Knee biomechanics in the deep squatting state after unicompartmental knee arthroplasty versus high tibial osteotomy: A 3-dimensional finite element study

Knee biomechanics in the deep squatting state after unicompartmental knee arthroplasty versus high tibial osteotomy: A 3-dimensional finite element study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Knee biomechanics in the deep squatting state after unicompartmental knee arthroplasty versus high tibial osteotomy: A 3-dimensional finite element study Ziheng Zhang, Baogang Wei, Yongxiang Wang, Bingxian Ma, Huricha Bao, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6740482/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective: Knee osteoarthritis (KOA) often necessitates surgical interventions like unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO), but their biomechanical responses during deep squatting. This three-dimensional finite element analysis (FEA) aimed to compare the mechanical behaviors of knees treated with UKA and open-wedge HTO (OW-HTO) during 120° squatting, providing insights for postoperative mechanical evaluations and patient management. Methods: Laser 3D scanning/MRI/CT data were used to construct 3D finite element models of the healthy knee, KOA knee, UKA knee and OW-HTO knee in 120° flexion conditions, and mechanical loads in the deep squat condition were applied to assess the stresses on the meniscus, cartilage, bone, ligaments, and implants under deep squat conditions. Results: The results showed that in the normal knee during deep squatting, the menisci had a symmetrical stress distribution. In KOA knees, there were significant stress increases and concentrations in the menisci, cartilage, and subchondral bone. UKA effectively reduced lateral meniscus stress, lateral femoral cartilage stress, and ligament stresses, restoring a more normal mechanical environment. In contrast, OW-HTO knees still had high meniscal, cartilage, and bone stresses, similar to the KOA state. The maximum stresses in the implants of both UKA and OW-HTO approached the fatigue limits of their materials, and high stresses at the bone-implant interfaces might lead to complications such as aseptic loosening. Conclusion: This study tentatively suggests that UKA is suitable for patients with high-frequency flexion demands, but there is a risk of aseptic loosening and fragmentation of the prosthesis, whereas HTO is suitable for young, well-boned patients with predominantly extra-articular deformities. Regardless of the procedure, prolonged knee flexion at large angles should be avoided to improve the prognosis. Knee osteoarthritis Unicompartmental knee arthroplasty High tibial osteotomy Squatting Finite element analysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction The diversity of occupations, sports, and cultures necessitates more frequent squatting in daily human activities. Unlike walking, squatting may impose negative impacts on the native knee joint structure and implanted prostheses, yet it also offers new perspectives for evaluating the functional and mechanical properties of post-operative knees ( 1 ). The mechanical behavior of the knee during squatting is closely linked to work types, population demographics, and cultural practices. Squatting can be categorized into three types based on knee flexion angles: partial squatting (approximately 40°), half squatting (70°-100°), and full squatting (>100°) ( 2 ). For example, occupations requiring frequent squatting, standing, or heavy lifting, such as construction workers and farmers ( 3 ), subject the knees to substantial loads, increasing susceptibility to joint wear and degeneration ( 1 , 4 ). Such mechanical demands significantly elevate intra articular stress and contact forces, potentially contributing to the early onset of knee osteoarthritis (KOA) ( 5 ). Unicompartmental arthroplasty (UKA) and high tibial osteotomy (HTO) serve as effective strategies to delay total knee arthroplasty (TKA) in active patients ( 6 , 7 ). However, the complex mechanical environment induced by squatting may accelerate KOA progression and cause implant related complications. Therefore, further analysis of the mechanical responses of post-operative knees and implants under squatting conditions is imperative to inform clinical practices and improve long-term outcomes. UKA corrects abnormal knee alignment by addressing articular surface wear, thus managing intra articular deformities, whereas HTO corrects abnormal knee alignment through modifying extra articular bony deformities, targeting deformities outside the joint compartment. While both procedures offer distinct advantages, the differences in post-operative knee mechanics between UKA and HTO remain under explored ( 8 , 9 ). Previous in vivo studies utilizing implant-borne sensors have evaluated tibiofemoral joint forces during squatting, but these were limited to a maximum knee flexion angle of approximately 100° and could not estimate contact pressures or stress distributions in soft tissues such as cartilage and menisci ( 10 ). Ex vivo experiments using cadaveric specimens allow quantification of joint contact forces and pressures, yet they suffer from the inability to compare multiple surgical techniques within the same specimen and lack the capacity to observe trends in contact surface stress distributions ( 11 – 13 ). These limitations hinder in-depth investigations. Finite element analysis (FEA), a computational simulation technique based on numerical methods, can model the mechanical behavior of complex structures under diverse loading conditions ( 14 – 16 ). A thorough understanding of the mechanical characteristics of knees treated with UKA and open-wedge HTO (OW-HTO) during deep squatting is therefore critical for evaluating post-operative functional recovery and long-term prognosis. This study aims to develop models of healthy knees, KOA, UKA and OW-HTO. Through FEA, we will compare the magnitude and distribution of contact stresses in the knee joints after UKA and OW-HTO during deep squatting, aiming to elucidate the mechanical similarities and differences between the two surgical approaches. 2. Methods 2.1. Knee 3D model creation One 55-year-old healthy female volunteer (height: 164 cm, weight: 58.9 kg) and one 57-year-old female patient with medial compartment KOA in the left knee (height: 166 cm, weight: 60.4 kg) were recruited (Fig. 1 A). After obtaining informed consent, scanning of lower limbs of volunteers using CT (Definition, SIEMENS Inc, Germany). MRI of the knee was conducted using a 3.0T superconducting scanner (Discovery 750w, General Electric Inc, USA) with the volunteer in lateral decubitus position. The study protocol was approved by the Ethics Committee of author’s institution and strictly adhered to ethical guidelines (Ethics Approval No. 202507305L). 3D models of the femur, tibia, tibiofemoral joint cartilage and meniscus were created using Mimics Research 20.0 (Materialise Inc, Belgium) (Fig. 1 B), Optimizations of the extracted structures by Geomagic Wrap 17.0 (Raindrop Inc, USA). Implant modelling by laser 3D scanner (FreeScan UE 11/13, Shining3D Inc, China) (Fig. 1 D). For the UKA, the Oxford®-IV cemented mobile-bearing UKA system (Zimmer Biomet Inc, USA) is selected (Fig. 1 C). As for the HTO, the left knee TomoFix plate of the fixation system is chosen. The most suitable implant model is selected according to the results of imaging measurement. In accordance with clinical standards, assembly of all components was performed using SolidWorks 2017 (Dassault Inc, France) (Fig. 1 E). 2.2. Material properties and meshing The models to be analyzed were imported into Ansys R17.0 (Synopsys Inc, USA). All models were meshed using tetrahedral elements (Table 1 ). When assigning material properties to the meshed structures, although bone, ligaments, menisci, and other tissues in the human body exhibit direction dependent physical properties, this study primarily focuses on comparing knee stress change trends across four flexion states. Given that this directional characteristic has less impact on the overall analysis and a relatively simplified knee model can reduce computational load, isotropic material properties were adopted for setup. The femoral component of the UKA prosthesis was constructed from cobalt chromium molybdenum alloy, the tibial component and TomoFix Plate from titanium alloy, and the bearing insert from ultra-high molecular weight polyethylene. Material property values for all structures were assigned based on established literature ( 17 – 20 ) (Table 2 ). Table 1 Elements and Nodes. Normal KOA UKA OW-HTO Nodes 253341 224884 244863 257463 Elements 147203 130578 142203 147621 Table 2 Material properties of each structure. Structure Young's modulus(MPa) Poisson's ratio Meniscus 27.5 0.33 Polyethylene Insert 685.0 0.40 Femoral component 220000.0 0.30 Bone cement 2400.0 0.45 Tibial component 110000.0 0.30 Screw 190000.0 0.27 TomoFix Plate 113000.0 0.33 Cortical bone 17000.0 0.30 Cancellous bone 350.0 0.25 Ligament 215.3 0.40 Cartilage 15.0 0.45 2.3. Boundary condition and loads The femur was permitted to undergo rotation, varus and valgus under ligamentous constraints, with the distal tibiofibular fully fixed. Frictional contact ( µ = 0.1) was defined both between femoral cartilage and menisci and within the patellofemoral joint, while all other contact pairs were set as bonded. To balance computational efficiency and anatomical fidelity, the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) were simplified appropriately in the model, ensuring structural realism was maintained. For all models, a single leg squatting deep squatting manoeuvre was simulated, with a 600 N vertical downward force applied from the proximal femur, and no other forces were set on the knee joint (Fig. 2 ). 3. Results 3.1. Validation of validity Given the current lack of reference finite element models of the knee in deep squat posture, validity verification was performed using a fully extended normal knee model. The femur was constrained with six degrees of freedom, while tibial and fibular flexion-extension degrees of freedom were restricted. An anterior thrust of 134 N was applied at the midpoints of the medial and lateral tibial plateaus to simulate the anterior drawer test, with displacement measured at the anterior tibial midpoint. The simulated anterior tibial displacement was 4.50 mm, comparable to the 4.75 mm reported by Geeslin et al. ( 21 ) (Fig. 2 E). Under a 1000 N vertical load applied to the femur, the resultant load distribution matched previous studies ( 22 ) (Fig. 2 F, 2 G), confirming the validity of the finite element knee model developed in this study. 3.2. Stress characteristics of the meniscus The distribution of loads on the medial and lateral meniscus of the normal knee was basically symmetrical in the deep squatting condition, and the peak meniscus stress in the KOA knee was significantly increased, and the lateral was higher than the medial, concentrating on the medial rim. The lateral meniscus stress was significantly decreased after UKA, whereas there was no significant improvement in the peak meniscus stress after OW-HTO compared to the preoperative period, but the concentration of the stress in the medial meniscus was alleviated compared to the preoperative period (Fig. 3 ). 3.3. Stress characteristics of cartilage and bone In the squatting state of KOA group, the stress on the medial and lateral femoral cartilages was approximately twice that of normal knee joints, with stress concentrated on the posterior part of the femoral condyle. After UKA, the stress on the lateral femoral cartilage decreased to a level basically consistent with that of the normal group. After OW-HTO, the stress on the medial and lateral femoral cartilages remained close to preoperative levels. The stress on the medial tibial cartilage in the KOA group was higher than that in the normal group. After UKA, the stress on the lateral tibial cartilage became basically consistent with that of the normal group, and the stress concentration improved compared with the preoperative state; after OW-HTO, it remained basically consistent with the preoperative state. The stress on the subchondral cortical bone in the KOA group was significantly higher than that in the normal group, decreasing to normal levels after UKA, while the cortical bone of the OW-HTO platform still bore higher loads. The stress on the cancellous bone after both UKA and OW-HTO was basically consistent with preoperative levels (Fig. 4 ). 3.4. Stress characteristics of ligaments The ACL and PCL stresses in the KOA group increased by about 2–3 times compared with the normal group in the deep squat condition. The ACL stresses in the UKA and OW-HTO groups were not significantly different from those in the preoperative period, but the distribution of the stresses in the UKA group was closer to that of the normal group. The distribution of the PCL stresses was basically the same in the KOA and the post-operative knees, but the peak value in the UKA group after the operation was closer to that of the normal group. The MCL stresses were higher than those in the normal group in the KOA group and decreased to normal after the UKA operation, but did not improve after the OW-HTO operation (Fig. 5 ). 3.5. Stress characteristics of implants and bone cements The stress distribution of each UKA prosthetic component in the deep squatting condition was biased towards the posterior side, and the trend of stress distribution at the cement interface and osteotomy interface was basically the same as the distribution of the high stress area of the prosthesis (Fig. 6 ).The stress distribution of the TomoFix plate was concentrated in the osteotomy opening area after OW-HTO, and the stress in the hinge area was concentrated in the junction of osteotomy area of the cortical bone and the hinge (Fig. 7 ). 3.6. Characterizations of maximum principal stress The maximum principal stresses in the meniscus of the normal knee in the deep squat condition were higher medially than laterally, and the femoral cartilage was basically the same medially and laterally. The meniscus and femoral cartilage stresses were higher than those in the normal knee in the KOA knee and were higher laterally than medially. The stresses of the lateral interstitial compartments were significantly decreased after UKA, and there was no significant change from the preoperative level after the OW-HTO procedure (Fig. 8 ). 4. Discussion 4.1 Mechanical differences between deep squat and standing conditions Clinically, it is generally recognized that femoral motion relative to the tibia during squatting generates higher joint pressures. Takuya et al. ( 23 ) calculated normal knee contact forces using gait testing combined with a musculoskeletal modeling system, revealing that knee contact forces increase linearly with knee flexion angle throughout the gait cycle. Conversely, Wang et al. ( 24 ) applied 400 N parallel to the femoral shaft and 300 N along the articular alignment load to knee specimens, observing an average 20° external rotation of the femur with 7mm posterior translation during 0–90° flexion. At 130° flexion, tibial internal rotation and femoral adduction significantly increased, with greater femoral posterior displacement causing the lateral condyle to lift off the tibial surface and contact the posterior horn of the meniscus. In KOA patients, Fukaya et al. ( 25 ) identified stress concentration at the medial meniscal margin in standing posture, inferring that narrowed medial joint space due to KOA leads to degenerative medial osteophyte formation, generating lateral thrust during standing that shifts tibial articular surface loads toward the medial margin. During deep squatting in normal knees, symmetrical von-Mises stress in medial and lateral menisci reflects physiological load balance. Wang et al. ( 24 ) observed nearly equal medial-lateral stresses during 0–90° flexion, with peak stress at 10 MPa in full extension decreasing to 6 MPa at 90°, whereas at 130° flexion, medial stress exceeded lateral with a peak of 21 MPa, more posteriorly concentrated on the femoral condyle compared to our normal group. This was attributed to increased femoral posterior displacement and lateral condyle lifting off the tibial surface, reducing tibiofemoral contact area and amplifying load-induced stress concentration. The higher peak stress in their study likely resulted from larger flexion angles and inclusion of lower limb alignment loads. In the KOA model, lateral meniscus stress surged to 26.167 MPa, higher than the normal group. We attribute this to two factors: 1) the KOA medial meniscus is thinner than normal, with the pressure center shifting posteriorly during flexion to act on the delicate medial margin, exacerbating stress concentration; 2) observation of tibial medial plateau cartilage stress and medial condyle stress distribution suggests partial medial meniscal dislocation in deep squatting, further reducing contact area and intensifying stress concentration. These findings indicate that alignment abnormalities disrupt joint surface compliance, imposing abnormal shear loads on menisci. The stress in the subchondral cortical bone of the KOA group is 80% higher than that of the normal group, which is associated with the tibial plateau posterior margin bearing the load during deep squatting. In contrast, trabecular bone stress post OW-HTO increased to 8.377 MPa, reflecting increased axial load borne by trabecular bone after osteotomy, contrasting with the cortical bone-dominated loading in standing posture. These differences highlight a more pronounced "stress amplification effect" of deep squatting in pathological and post-operative knees, particularly when joint surface integrity is compromised or alignment is altered. In patients with KOA, ACL stress was twice as high as in normal subjects, and PCL stress was 2.7 times higher than in the normal group. Such abnormal high stresses are likely caused by reduced joint stability, as the ACL and PCL normally restrict tibial translation relative to the femur in healthy knees. However, in KOA, articular cartilage wear leads to narrowed joint space, varus malalignment, and increased tibial plateau posterior slope, forcing these ligaments to bear greater stress to maintain joint stability. This compensatory mechanism may contribute to ligament damage, Rajgopal et al. ( 26 ) proposed that ACL injury during osteoarthritis progression induces kinematic changes, leading to posterior wear of medial and lateral femoral condyles, that aligns with our observation of elevated medial condyle stress in KOA. Additionally, an MRI imaging study carried out by Biswal et al. ( 27 ) found that ACL tears will result in rapid degradation of the tibial cartilage, with cartilage damage located anteriorly or posteriorly progressing faster than that located centrally, which is the same trend we observed in the distribution of high stress areas in the tibial cartilage of the KOA knee. 4.2 Mechanics-related effects of implants in the deep squat condition Prosthetic failure is one of the catastrophic complications of UKA and OW-HTO ( 28 ). Aseptic loosening and periprosthetic fractures account for 36% and 21% of revision cases in knee arthroplasty, respectively, which are closely associated with prosthetic materials, implantation techniques, and mechanical loading ( 29 ). The yield strength of Co-Cr-Mo alloy is about 800–1000 MPa in previous studies ( 30 ), while the fatigue limit of Ti-6Al-4V in air is 750 MPa, but related studies have found that the fatigue limit decreases to about 450 MPa in a simulated human environment (0.9% NaCl solution) ( 31 ). In this study, peak stresses in the UKA tibial component during deep squatting were observed to be 419.17 MPa, whereas femoral component and OW-HTO implant stresses reached 1075.6 MPa and 668.74 MPa, respectively, which basically reached the fatigue limit of each material, and repeated deep squatting may lead to fatigue cracking of the prosthetic component. Stress gradients at the bone implant interface may induce interfacial micromotion, which over time can lead to fatigue fracture of the bone cement. Previous studies indicate that the yield strength of bone cement typically ranges from 30–50 MPa, with fatigue cracks often originating at the bone-cement interface where crack initiation occurs at stress levels equivalent to 40–50% percent of its ultimate strength. In physiological environments (0.9% NaCl solution), the fatigue life of bone cement is shorter than in air ( 32 , 33 ). During deep squatting in this study, stress concentrated at the posterior margin of both femoral and tibial-cement interfaces, exceeding the yield strength of bone cement and posing a high risk of cement fragmentation. On the other hand, trabecular bone, as a porous network structure, has a strength limit closely associated with trabecular density, orientation, and mineral content. Experimental evidence shows that the compressive strength limit of knee trabecular bone ranges from approximately 1.5-8 MPa ( 34 ), in contrast to 100–200 MPa for cortical bone ( 35 ). While trabecular bone stresses at the bone cement interface in this study remained below these thresholds, the cortical bone stress at the femoral osteotomy interface after UKA reached 344.15 MPa. This "stress overload" may induce interfacial micromotion, accelerating interfacial bone resorption and collapse, and ultimately leading to fractures. Such mechanical behavior represents a critical factor contributing to prosthetic loosening after UKA. Due to the significantly higher Young’s modulus of metallic implants compared to human bone tissue, loads are transferred through the prosthesis rather than the surrounding bone, inducing a stress shielding effect. Following implantation, this effect occurs during knee flexion, manifesting as uneven stress distribution at the bone cement layer and osteotomy interface in this study, particularly severe on the tibial side of the UKA group. Stress shielding often leads to osteoporosis and osteolysis, which are closely associated with implant loosening and periprosthetic fractures ( 36 ). In this study, cortical bone stress at the tibial osteotomy surface was most concentrated in full extension, located at the anterior margin of the UKA osteotomy surface and the trabecular bone osteotomy surface of the OW-HTO group. This may activate osteoclast activity, leading to bone resorption at the osteotomy site or delayed nonunion in the hinge region ( 30 , 37 ). 4.3 Negative effects of deep squatting on knee joint structure The high stress states in menisci and ligaments during deep squatting pose potential threats to post-operative outcomes. Mononen et al. ( 38 ) developed an algorithm based on tissue biomechanics and computational simulation to model KOA progression, in which excessive maximum principal stress drives iterative reduction in collagen network stiffness. Their analysis determined a threshold of 5–7 MPa for maximum principal stress in collagen fiber degeneration. This study found that maximum principal stresses in menisci of both the normal and KOA groups exceeded this threshold, suggesting a long-term risk for meniscal fibrosis or tears. Daszkiewicz et al. ( 39 ) attributed such differences primarily to increased circumferential stress, demonstrating in their simulations that medial meniscal circumferential stress in the KOA model was 7-fold higher than in healthy knees at 0° knee flexion. Such elevated circumferential stress commonly leads to radial tears in the mid-posterior meniscus and posterior horn injuries. In the OW-HTO group, however, medial ligament stresses in both the arthritic and post OW-HTO states exceeded normal levels, resulting in ineffective medial compartment decompression. Neither maximum von-Mises stress nor maximum principal stress showed significant changes compared to the preoperative KOA state. Cartilage degeneration also signals further progression of KOA. Kerin et al. ( 40 ) measured the compressive strength range of normal adult knee cartilage as 3–10 MPa through in vitro compression tests. Malekipour et al. ( 41 ) combined impact tests with finite element analysis to propose that microdamage occurs in cartilage-bone complexes when peak stress exceeds 12 MPa. In this study, the distribution trend of maximum principal stress in the KOA knee was generally consistent with that in the normal knee, but the high-stress regions were more extensive. In the post UKA group, replacing the medial compartment restored normal joint space, and load by the prosthesis helped reduce lateral femoral cartilage stress to normal levels. In the OW-HTO group, femoral cartilage changes mirrored those in the menisci, which we attribute to insufficient release of the MCL. Van Egmond et al. ( 42 ) demonstrated through OW-HTO modeling that release of the superficial MCL helps reduce medial compartment pressure. Bagherifard et al. ( 43 ) reported via imaging measurements that 30 OW-HTO patients showed a 71.5% average reduction in medial joint space compared to preoperative levels, indicating that appropriate superficial MCL release aids in load transfer from the medial compartment consistent with our observations. However, as critical stabilizers, bone and cartilage tissue exhibit specific stress distributions during deep squatting, which warrants further analysis through full-cycle mechanical simulations. 4.4 Limitations of the study This time, we only focus on the mechanical situation under the specific condition of 120° squat, and the mechanical change of the dynamic process from standing to squatting is still unclear, and the results can not be extended to illustrate the mechanical state of more angles. Secondly, the setting of each result of the knee joint as isotropic material, as well as the simplified processing of some structures, inevitably differ from the real knee joint state, thus causing errors in the experimental results, and these shortcomings will be improved in further research. 5. Conclusion Squatting significantly increases stress on various structures of the knee joint. UKA reconstructs knee joint load balance by replacing the medial diseased compartment, demonstrating better adaptability for patients with high demands for frequent flexion movements such as squatting. However, the stress on UKA prosthetic components approaches the material fatigue limit, posing risks of aseptic loosening and prosthetic fragmentation. While HTO maximally preserves the original knee joint structure, it exhibits a tendency for accelerated degeneration during squatting, necessitating attention to MCL release during surgery. In future personalized treatment, there should be further integration of patient activity levels, deformity types, and soft tissue status to comprehensively evaluate the biomechanical adaptability of surgical procedures, aiming to achieve better prognoses. Abbreviations KOA Knee osteoarthritis UKA Unicompartmental knee arthroplasty HTO High tibial osteotomy OW-HTO Open-wedge HTO FEA Finite element analysis ACL Anterior cruciate ligament PCL Posterior cruciate ligament MCL Medial collateral ligament LCL lateral collateral ligament TKA Total knee arthroplasty Declarations Acknowledgements We would like to express our gratitude to all participants for their contributions. Author contributions Conception and design of the study: Z-H Z and Y-S Q; Acquisition of data: Z-H Z, Y-S Q, B-G W, Y-X W; Analyses of data: Z-H Z and B-X M; Drafting the work: Z-H Z and H-R-C B; Revising it critically for important intellectual content: Z Z and Y-S X; All authors approved the final version of the manuscript. Funding This study was supported by the National Natural Science Foundation of China (Grant numbers: 82172444, 81960399), the Natural Science Foundation of Inner Mongolia Autonomous Region (2024ZD32), the Science and Technology Plan Project of Inner Mongolia Autonomous Region (2023YFSH0020, 2022YFSH0053, 2021GG0127) and the Science and Technology Plan Project of Wuhai(2023WHSKJJH06). Data availability All relevant data supporting the conclusions are included within the article and tables. The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request. Ethical approval From The Ethics Committee of Inner Mongolia Autonomous Region People's Hospital approved this study (No. 202507305L). Informed consent Informed consent was obtained from all individual participants included in the study. All methods were performed in accordance with the guidelines and regulations of the Ethics Committee of Inner Mongolia Autonomous Region People's Hospital. Our study adhered to the Declaration of Helsinki. Consent for publication Not applicable. Competing interests The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Clinical trial number Not applicable. Author details 1 Orthopedic Center (Sports Medicine Center), Inner Mongolia Autonomous Region People's Hospital, Hohhot, 010017, China 2 The People's Hospital of Wu Hai Inner Mongolia, Wuhai, 016000, China References Jahn J, Ehlen QT, Huang CY. Finding the Goldilocks Zone of Mechanical Loading: A Comprehensive Review of Mechanical Loading in the Prevention and Treatment of Knee Osteoarthritis. Bioengineering (Basel). 2024;11(2). Schoenfeld BJ. Squatting kinematics and kinetics and their application to exercise performance. J Strength Cond Res. 2010;24(12):3497-506. Cooper C, McAlindon T, Coggon D, Egger P, Dieppe P. Occupational activity and osteoarthritis of the knee. Ann Rheum Dis. 1994;53(2):90-3. Hartmann H, Wirth K, Klusemann M. Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load. Sports Med. 2013;43(10):993-1008. Mulholland SJ, Wyss UP. Activities of daily living in non-Western cultures: range of motion requirements for hip and knee joint implants. Int J Rehabil Res. 2001;24(3):191-8. Cao Z, Mai X, Wang J, Feng E, Huang Y. Unicompartmental Knee Arthroplasty vs High Tibial Osteotomy for Knee Osteoarthritis: A Systematic Review and Meta-Analysis. J Arthroplasty. 2018;33(3):952-9. Debopadhaya S, Acosta E, Ortiz D, 3rd. Trends and outcomes in the surgical management of young adults with knee osteoarthritis using high tibial osteotomy and unicompartmental knee arthroplasty. Arch Orthop Trauma Surg. 2024;144(9):3995-4002. Koh IJ, Kim MS, Sohn S, Song KY, Choi NY, Jung H, In Y. Predictive factors for satisfaction after contemporary unicompartmental knee arthroplasty and high tibial osteotomy in isolated medial femorotibial osteoarthritis. Orthop Traumatol Surg Res. 2019;105(1):77-83. Ping H, Wen J, Liu Y, Li H, Wang X, Kong X, Chai W. Unicompartmental knee arthroplasty is associated with lower pain levels but inferior range of motion, compared with high tibial osteotomy: a systematic overview of meta-analyses. J Orthop Surg Res. 2022;17(1):425. Kothurkar R, Lekurwale R. Techniques to determine knee joint contact forces during squatting: A systematic review. Proc Inst Mech Eng H. 2022;236(6):775-84. Hale R, Green J, Hausselle J, Saxby D, Gonzalez RV. Quantified in vitro tibiofemoral contact during bodyweight back squats. J Biomech. 2018;79:21-30. Churchill DL, Incavo SJ, Johnson CC, Beynnon BD. The influence of femoral rollback on patellofemoral contact loads in total knee arthroplasty. J Arthroplasty. 2001;16(7):909-18. Wunschel M, Leichtle U, Obloh C, Wulker N, Muller O. The effect of different quadriceps loading patterns on tibiofemoral joint kinematics and patellofemoral contact pressure during simulated partial weight-bearing knee flexion. Knee Surg Sports Traumatol Arthrosc. 2011;19(7):1099-106. Shu J, Zheng N, Teng H, Tsai TY, Liu Z. In vivo biomechanical dynamic simulation of a healthy knee during the single-leg lunge and its experiment validation. Med Eng Phys. 2024;129:104183. Pfeiffer FM. The Use of Finite Element Analysis to Enhance Research and Clinical Practice in Orthopedics. J Knee Surg. 2016;29(2):149-58. Zhang ZH, Qi YS, Wei BG, Bao HR, Xu YS. Application strategy of finite element analysis in artificial knee arthroplasty. Front Bioeng Biotechnol. 2023;11:1127289. Kang KT, Son J, Suh DS, Kwon SK, Kwon OR, Koh YG. Patient-specific medial unicompartmental knee arthroplasty has a greater protective effect on articular cartilage in the lateral compartment: A Finite Element Analysis. Bone Joint Res. 2018;7(1):20-7. Wen PF, Guo WS, Gao FQ, Zhang QD, Yue JA, Cheng LM, Zhu GD. Effects of Lower Limb Alignment and Tibial Component Inclination on the Biomechanics of Lateral Compartment in Unicompartmental Knee Arthroplasty. Chin Med J (Engl). 2017;130(21):2563-8. Pan CS, Wang X, Ding LZ, Zhu XP, Xu WF, Huang LX. The best position of bone grafts in the medial open-wedge high tibial osteotomy: A finite element analysis. Comput Methods Programs Biomed. 2023;228:107253. Armillotta N, Bori E, Innocenti B. Finite element analysis of malposition in bi-unicompartmental knee arthroplasty. Arch Orthop Trauma Surg. 2023;143(6):3447-55. Geeslin AG, Civitarese D, Turnbull TL, Dornan GJ, Fuso FA, LaPrade RF. Influence of lateral meniscal posterior root avulsions and the meniscofemoral ligaments on tibiofemoral contact mechanics. Knee Surg Sports Traumatol Arthrosc. 2016;24(5):1469-77. Bao HR, Zhu D, Gong H, Gu GS. The effect of complete radial lateral meniscus posterior root tear on the knee contact mechanics: a finite element analysis. J Orthop Sci. 2013;18(2):256-63. Mitani T, Inoue K, Takahashi S. Relationship between joint angle and contact force at the knee during normal gait. J Adv Mech Des Syst Manuf. 2025;19(2):9. Wang J, Tao K, Li H, Wang C. Modelling and analysis on biomechanical dynamic characteristics of knee flexion movement under squatting. ScientificWorldJournal. 2014;2014:321080. Fukaya T, Mutsuzaki H, Aoyama T, Watanabe K, Mori K. A Simulation Case Study of Knee Joint Compressive Stress during the Stance Phase in Severe Knee Osteoarthritis Using Finite Element Method. Medicina (Kaunas). 2021;57(6). Rajgopal A, Noble PC, Vasdev A, Ismaily SK, Sawant A, Dahiya V. Wear Patterns in Knee Articular Surfaces in Varus Deformity. J Arthroplasty. 2015;30(11):2012-6. Biswal S, Hastie T, Andriacchi TP, Bergman GA, Dillingham MF, Lang P. Risk factors for progressive cartilage loss in the knee: a longitudinal magnetic resonance imaging study in forty-three patients. Arthritis Rheum. 2002;46(11):2884-92. Fisher CR, Patel R. Profiling the Immune Response to Periprosthetic Joint Infection and Non-Infectious Arthroplasty Failure. Antibiotics (Basel). 2023;12(2). Kim S, Baril C, Rudraraju S, Ploeg HL. Influence of Porosity on Fracture Toughness and Fracture Behavior of Antibiotic-Loaded PMMA Bone Cement. J Biomech Eng. 2022;144(1). Zeng L, Xiang N, Wei B. A COMPARISON OF CORROSION RESISTANCE OF COBALT-CHROMIUM-MOLYBDENUM METAL CERAMIC ALLOY FABRICATED WITH SELECTIVE LASER MELTING AND TRADITIONAL PROCESSING. Journal of Prosthetic Dentistry. 2014;112(5):1217-24. dos Santos SV, Lima GD, Santos RCS, Nascimento BL, Griza S. Fatigue and Corrosion Fatigue of Thermally Oxidized Ti6Al4V Alloy. J Mater Eng Perform. 2024:8. Roemhildt ML, McGee TD, Wagner SD. Novel calcium phosphate composite bone cement: strength and bonding properties. J Mater Sci Mater Med. 2003;14(2):137-41. Dunne NJ, Orr JF, Mushipe MT, Eveleigh RJ. The relationship between porosity and fatigue characteristics of bone cements. Biomaterials. 2003;24(2):239-45. Hvid I. Mechanical strength of trabecular bone at the knee. Dan Med Bull. 1988;35(4):345-65. Wachter NJ, Krischak GD, Mentzel M, Sarkar MR, Ebinger T, Kinzl L, et al. Correlation of bone mineral density with strength and microstructural parameters of cortical bone in vitro. Bone. 2002;31(1):90-5. Bori E, Armaroli F, Innocenti B. Biomechanical analysis of femoral stems in hinged total knee arthroplasty in physiological and osteoporotic bone. Comput Methods Programs Biomed. 2022;213:106499. Galas A, Banci L, Innocenti B. The Effects of Different Femoral Component Materials on Bone and Implant Response in Total Knee Arthroplasty: A Finite Element Analysis. Materials (Basel). 2023;16(16). Mononen ME, Tanska P, Isaksson H, Korhonen RK. A Novel Method to Simulate the Progression of Collagen Degeneration of Cartilage in the Knee: Data from the Osteoarthritis Initiative. Sci Rep. 2016;6:21415. Daszkiewicz K, Luczkiewicz P. Biomechanics of the medial meniscus in the osteoarthritic knee joint. PeerJ. 2021;9:e12509. Kerin AJ, Wisnom MR, Adams MA. The compressive strength of articular cartilage. Proc Inst Mech Eng H. 1998;212(4):273-80. Malekipour F, Oetomo D, Lee PV. Equine subchondral bone failure threshold under impact compression applied through articular cartilage. J Biomech. 2016;49(10):2053-9. van Egmond N, Hannink G, Janssen D, Vrancken AC, Verdonschot N, van Kampen A. Relaxation of the MCL after an Open-Wedge High Tibial Osteotomy results in decreasing contact pressures of the knee over time. Knee Surg Sports Traumatol Arthrosc. 2017;25(3):800-7. Bagherifard A, Jabalameli M, Mirzaei A, Khodabandeh A, Abedi M, Yahyazadeh H. Retaining the medial collateral ligament in high tibial medial open-wedge osteotomy mostly results in post-operative intra-articular gap reduction. Knee Surg Sports Traumatol Arthrosc. 2020;28(5):1388-93. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6740482","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":472572714,"identity":"fd5bd11b-a9af-4f20-a981-075b9a62239d","order_by":0,"name":"Ziheng Zhang","email":"","orcid":"","institution":"Inner Mongolia Autonomous Region People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ziheng","middleName":"","lastName":"Zhang","suffix":""},{"id":472572715,"identity":"8e9ab5dc-1388-4109-a250-7d81d00c3d40","order_by":1,"name":"Baogang Wei","email":"","orcid":"","institution":"Inner Mongolia Autonomous Region People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Baogang","middleName":"","lastName":"Wei","suffix":""},{"id":472572716,"identity":"0f637cd4-6f2c-4211-9b1b-d82ba0415aac","order_by":2,"name":"Yongxiang Wang","email":"","orcid":"","institution":"Inner Mongolia Autonomous Region People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yongxiang","middleName":"","lastName":"Wang","suffix":""},{"id":472572717,"identity":"55ac4f5e-5558-4b03-b710-d29457a12b4f","order_by":3,"name":"Bingxian Ma","email":"","orcid":"","institution":"Inner Mongolia Autonomous Region People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Bingxian","middleName":"","lastName":"Ma","suffix":""},{"id":472572718,"identity":"2aa0f49a-b8c6-4997-9455-979d5cb7e2a1","order_by":4,"name":"Huricha Bao","email":"","orcid":"","institution":"Inner Mongolia Autonomous Region People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Huricha","middleName":"","lastName":"Bao","suffix":""},{"id":472572719,"identity":"f24a3576-8c79-4a10-86d9-715a506b9665","order_by":5,"name":"Zhong Zhang","email":"","orcid":"","institution":"The People's Hospital of Wu Hai Inner Mongolia","correspondingAuthor":false,"prefix":"","firstName":"Zhong","middleName":"","lastName":"Zhang","suffix":""},{"id":472572720,"identity":"c9fe086a-3dc3-4dfa-9d79-fcbfa7a5ede2","order_by":6,"name":"Yongsheng Xu","email":"","orcid":"","institution":"Inner Mongolia Autonomous Region People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yongsheng","middleName":"","lastName":"Xu","suffix":""},{"id":472572721,"identity":"f950923a-963c-40f0-9573-9b767f706b4a","order_by":7,"name":"Yansong Qi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyklEQVRIiWNgGAWjYFAC5gYGBgMGfgb2xsYHH4jTwgjWItnAc7jZcAbxWhiAWiTS26Q5iNGg236w8cObgjsSBjcfNkgzMNjJ6TYQ0GJ2JrFZco7BMwmD24kNxgUMycZmBwhpOZDYIM1jcLgOpCV5BsOBxG0EtZx/2PwbqAXosIMNh3mI0nIjsU0arOUGY2MzkVoetlnOAWqRBHqKcYYBMX45n3z4xps/hyX4jh9//uNDhZ0cQS1gwANnGRCjHFXLKBgFo2AUjAIsAACAJ0mQjzWDdwAAAABJRU5ErkJggg==","orcid":"","institution":"Inner Mongolia Autonomous Region People's Hospital","correspondingAuthor":true,"prefix":"","firstName":"Yansong","middleName":"","lastName":"Qi","suffix":""}],"badges":[],"createdAt":"2025-05-24 18:23:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6740482/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6740482/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85069023,"identity":"f5de5f5a-ad31-475b-ab08-74c92b41bd9e","added_by":"auto","created_at":"2025-06-20 15:27:09","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":675178,"visible":true,"origin":"","legend":"\u003cp\u003eFinite element model building and assembly. KOA patient (A), extraction of bone and soft tissue (B), TomoFix plate and UKA prosthesis (C), implant surface treatment and 3D scanning (D), Complete knee model (E).\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/6d750399462686faa73c6c31.png"},{"id":85069026,"identity":"1a5f1e31-ba8f-452e-93c0-4df3b5dbb32d","added_by":"auto","created_at":"2025-06-20 15:27:09","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":809848,"visible":true,"origin":"","legend":"\u003cp\u003eModels and validation of 0°. 600 N vertical downward force applied to the proximal femoral section of normal knee (A), KOA knee (B), post UKA (C), post OW-HTO (D), anterior drawer test was simulated to observe tibial displacement along the force direction (E), femoral cartilage stress distribution (F), tibial plateau cartilage stress distribution (G).\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/b404104706ff81faedecebc0.png"},{"id":85071859,"identity":"24c3bd79-6bcc-4e1a-9a91-d5e2b66a8884","added_by":"auto","created_at":"2025-06-20 15:43:09","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":302989,"visible":true,"origin":"","legend":"\u003cp\u003eVon-Mises stress and distribution of the meniscus.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/e4aaec061b06f2cd7a92c56a.png"},{"id":85069030,"identity":"96849164-0d61-4f54-990e-3920d226d165","added_by":"auto","created_at":"2025-06-20 15:27:09","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1037998,"visible":true,"origin":"","legend":"\u003cp\u003eVon-Mises stress and distribution of bone and cartilage.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/dc47505cd3b102c60d9bf1ea.png"},{"id":85069032,"identity":"9d3da6ba-1623-4a27-a0df-e374e5b40488","added_by":"auto","created_at":"2025-06-20 15:27:09","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1310472,"visible":true,"origin":"","legend":"\u003cp\u003eVon-Mises stress and distribution of knee ligaments.\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/a7e4c60e0058659df41bca48.png"},{"id":85070262,"identity":"b070fa1e-98c6-4189-a663-fe91c2f9380d","added_by":"auto","created_at":"2025-06-20 15:35:09","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":444091,"visible":true,"origin":"","legend":"\u003cp\u003eVon-Mises stress and distribution of the UKA prosthetic component, bone cement and osteotomy interface.\u003c/p\u003e","description":"","filename":"Figure6.png","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/0a661673250a5535a43a750e.png"},{"id":85070261,"identity":"9ca89f36-31d4-428b-838c-a0429dbb6853","added_by":"auto","created_at":"2025-06-20 15:35:09","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":332025,"visible":true,"origin":"","legend":"\u003cp\u003eVon-Mises stress and distribution of the OW-HTO implant and hinge region.\u003c/p\u003e","description":"","filename":"Figure7.png","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/56d760ca0d5ceff2d0081c5e.png"},{"id":85069039,"identity":"b795db3b-97e7-43a4-9ad9-4e04a97b946b","added_by":"auto","created_at":"2025-06-20 15:27:09","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":708661,"visible":true,"origin":"","legend":"\u003cp\u003eMaximum principal stress and distribution in the structure associated with the degeneration.\u003c/p\u003e","description":"","filename":"Figure8.png","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/d34a6449833d6f2ac4934bc3.png"},{"id":88633616,"identity":"407f8857-aa41-48e4-b413-21424607360c","added_by":"auto","created_at":"2025-08-08 14:32:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6769245,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6740482/v1/27a90c86-0c7d-4101-9118-0b53e6c6c1f8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Knee biomechanics in the deep squatting state after unicompartmental knee arthroplasty versus high tibial osteotomy: A 3-dimensional finite element study","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe diversity of occupations, sports, and cultures necessitates more frequent squatting in daily human activities. Unlike walking, squatting may impose negative impacts on the native knee joint structure and implanted prostheses, yet it also offers new perspectives for evaluating the functional and mechanical properties of post-operative knees (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). The mechanical behavior of the knee during squatting is closely linked to work types, population demographics, and cultural practices. Squatting can be categorized into three types based on knee flexion angles: partial squatting (approximately 40\u0026deg;), half squatting (70\u0026deg;-100\u0026deg;), and full squatting (\u0026gt;100\u0026deg;) (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). For example, occupations requiring frequent squatting, standing, or heavy lifting, such as construction workers and farmers (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e), subject the knees to substantial loads, increasing susceptibility to joint wear and degeneration (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Such mechanical demands significantly elevate intra articular stress and contact forces, potentially contributing to the early onset of knee osteoarthritis (KOA) (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Unicompartmental arthroplasty (UKA) and high tibial osteotomy (HTO) serve as effective strategies to delay total knee arthroplasty (TKA) in active patients (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). However, the complex mechanical environment induced by squatting may accelerate KOA progression and cause implant related complications. Therefore, further analysis of the mechanical responses of post-operative knees and implants under squatting conditions is imperative to inform clinical practices and improve long-term outcomes.\u003c/p\u003e \u003cp\u003eUKA corrects abnormal knee alignment by addressing articular surface wear, thus managing intra articular deformities, whereas HTO corrects abnormal knee alignment through modifying extra articular bony deformities, targeting deformities outside the joint compartment. While both procedures offer distinct advantages, the differences in post-operative knee mechanics between UKA and HTO remain under explored (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Previous in vivo studies utilizing implant-borne sensors have evaluated tibiofemoral joint forces during squatting, but these were limited to a maximum knee flexion angle of approximately 100\u0026deg; and could not estimate contact pressures or stress distributions in soft tissues such as cartilage and menisci (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). Ex vivo experiments using cadaveric specimens allow quantification of joint contact forces and pressures, yet they suffer from the inability to compare multiple surgical techniques within the same specimen and lack the capacity to observe trends in contact surface stress distributions (\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). These limitations hinder in-depth investigations. Finite element analysis (FEA), a computational simulation technique based on numerical methods, can model the mechanical behavior of complex structures under diverse loading conditions (\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). A thorough understanding of the mechanical characteristics of knees treated with UKA and open-wedge HTO (OW-HTO) during deep squatting is therefore critical for evaluating post-operative functional recovery and long-term prognosis.\u003c/p\u003e \u003cp\u003eThis study aims to develop models of healthy knees, KOA, UKA and OW-HTO. Through FEA, we will compare the magnitude and distribution of contact stresses in the knee joints after UKA and OW-HTO during deep squatting, aiming to elucidate the mechanical similarities and differences between the two surgical approaches.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Knee 3D model creation\u003c/h2\u003e \u003cp\u003eOne 55-year-old healthy female volunteer (height: 164 cm, weight: 58.9 kg) and one 57-year-old female patient with medial compartment KOA in the left knee (height: 166 cm, weight: 60.4 kg) were recruited (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). After obtaining informed consent, scanning of lower limbs of volunteers using CT (Definition, SIEMENS Inc, Germany). MRI of the knee was conducted using a 3.0T superconducting scanner (Discovery 750w, General Electric Inc, USA) with the volunteer in lateral decubitus position. The study protocol was approved by the Ethics Committee of author\u0026rsquo;s institution and strictly adhered to ethical guidelines (Ethics Approval No. 202507305L). 3D models of the femur, tibia, tibiofemoral joint cartilage and meniscus were created using Mimics Research 20.0 (Materialise Inc, Belgium) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB), Optimizations of the extracted structures by Geomagic Wrap 17.0 (Raindrop Inc, USA). Implant modelling by laser 3D scanner (FreeScan UE 11/13, Shining3D Inc, China) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD). For the UKA, the Oxford\u0026reg;-IV cemented mobile-bearing UKA system (Zimmer Biomet Inc, USA) is selected (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC). As for the HTO, the left knee TomoFix plate of the fixation system is chosen. The most suitable implant model is selected according to the results of imaging measurement. In accordance with clinical standards, assembly of all components was performed using SolidWorks 2017 (Dassault Inc, France) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eE).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Material properties and meshing\u003c/h2\u003e \u003cp\u003eThe models to be analyzed were imported into Ansys R17.0 (Synopsys Inc, USA). All models were meshed using tetrahedral elements (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). When assigning material properties to the meshed structures, although bone, ligaments, menisci, and other tissues in the human body exhibit direction dependent physical properties, this study primarily focuses on comparing knee stress change trends across four flexion states. Given that this directional characteristic has less impact on the overall analysis and a relatively simplified knee model can reduce computational load, isotropic material properties were adopted for setup. The femoral component of the UKA prosthesis was constructed from cobalt chromium molybdenum alloy, the tibial component and TomoFix Plate from titanium alloy, and the bearing insert from ultra-high molecular weight polyethylene. Material property values for all structures were assigned based on established literature (\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eElements and Nodes.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNormal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKOA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eUKA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOW-HTO\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNodes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e253341\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e224884\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e244863\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e257463\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElements\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e147203\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e130578\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e142203\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e147621\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMaterial properties of each structure.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStructure\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYoung's modulus(MPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePoisson's ratio\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMeniscus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e27.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePolyethylene Insert\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e685.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemoral component\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e220000.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBone cement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2400.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTibial component\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e110000.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eScrew\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e190000.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTomoFix Plate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e113000.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCortical bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17000.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCancellous bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e350.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLigament\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e215.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCartilage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Boundary condition and loads\u003c/h2\u003e \u003cp\u003eThe femur was permitted to undergo rotation, varus and valgus under ligamentous constraints, with the distal tibiofibular fully fixed. Frictional contact (\u003cem\u003e\u0026micro;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.1) was defined both between femoral cartilage and menisci and within the patellofemoral joint, while all other contact pairs were set as bonded. To balance computational efficiency and anatomical fidelity, the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) were simplified appropriately in the model, ensuring structural realism was maintained. For all models, a single leg squatting deep squatting manoeuvre was simulated, with a 600 N vertical downward force applied from the proximal femur, and no other forces were set on the knee joint (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Validation of validity\u003c/h2\u003e \u003cp\u003eGiven the current lack of reference finite element models of the knee in deep squat posture, validity verification was performed using a fully extended normal knee model. The femur was constrained with six degrees of freedom, while tibial and fibular flexion-extension degrees of freedom were restricted. An anterior thrust of 134 N was applied at the midpoints of the medial and lateral tibial plateaus to simulate the anterior drawer test, with displacement measured at the anterior tibial midpoint. The simulated anterior tibial displacement was 4.50 mm, comparable to the 4.75 mm reported by Geeslin et al. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE). Under a 1000 N vertical load applied to the femur, the resultant load distribution matched previous studies (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eF, \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eG), confirming the validity of the finite element knee model developed in this study.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Stress characteristics of the meniscus\u003c/h2\u003e \u003cp\u003eThe distribution of loads on the medial and lateral meniscus of the normal knee was basically symmetrical in the deep squatting condition, and the peak meniscus stress in the KOA knee was significantly increased, and the lateral was higher than the medial, concentrating on the medial rim. The lateral meniscus stress was significantly decreased after UKA, whereas there was no significant improvement in the peak meniscus stress after OW-HTO compared to the preoperative period, but the concentration of the stress in the medial meniscus was alleviated compared to the preoperative period (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Stress characteristics of cartilage and bone\u003c/h2\u003e \u003cp\u003eIn the squatting state of KOA group, the stress on the medial and lateral femoral cartilages was approximately twice that of normal knee joints, with stress concentrated on the posterior part of the femoral condyle. After UKA, the stress on the lateral femoral cartilage decreased to a level basically consistent with that of the normal group. After OW-HTO, the stress on the medial and lateral femoral cartilages remained close to preoperative levels. The stress on the medial tibial cartilage in the KOA group was higher than that in the normal group. After UKA, the stress on the lateral tibial cartilage became basically consistent with that of the normal group, and the stress concentration improved compared with the preoperative state; after OW-HTO, it remained basically consistent with the preoperative state. The stress on the subchondral cortical bone in the KOA group was significantly higher than that in the normal group, decreasing to normal levels after UKA, while the cortical bone of the OW-HTO platform still bore higher loads. The stress on the cancellous bone after both UKA and OW-HTO was basically consistent with preoperative levels (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Stress characteristics of ligaments\u003c/h2\u003e \u003cp\u003eThe ACL and PCL stresses in the KOA group increased by about 2\u0026ndash;3 times compared with the normal group in the deep squat condition. The ACL stresses in the UKA and OW-HTO groups were not significantly different from those in the preoperative period, but the distribution of the stresses in the UKA group was closer to that of the normal group. The distribution of the PCL stresses was basically the same in the KOA and the post-operative knees, but the peak value in the UKA group after the operation was closer to that of the normal group. The MCL stresses were higher than those in the normal group in the KOA group and decreased to normal after the UKA operation, but did not improve after the OW-HTO operation (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.5. Stress characteristics of implants and bone cements\u003c/h2\u003e \u003cp\u003eThe stress distribution of each UKA prosthetic component in the deep squatting condition was biased towards the posterior side, and the trend of stress distribution at the cement interface and osteotomy interface was basically the same as the distribution of the high stress area of the prosthesis (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).The stress distribution of the TomoFix plate was concentrated in the osteotomy opening area after OW-HTO, and the stress in the hinge area was concentrated in the junction of osteotomy area of the cortical bone and the hinge (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.6. Characterizations of maximum principal stress\u003c/h2\u003e \u003cp\u003eThe maximum principal stresses in the meniscus of the normal knee in the deep squat condition were higher medially than laterally, and the femoral cartilage was basically the same medially and laterally. The meniscus and femoral cartilage stresses were higher than those in the normal knee in the KOA knee and were higher laterally than medially. The stresses of the lateral interstitial compartments were significantly decreased after UKA, and there was no significant change from the preoperative level after the OW-HTO procedure (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Mechanical differences between deep squat and standing conditions\u003c/h2\u003e \u003cp\u003eClinically, it is generally recognized that femoral motion relative to the tibia during squatting generates higher joint pressures. Takuya et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e) calculated normal knee contact forces using gait testing combined with a musculoskeletal modeling system, revealing that knee contact forces increase linearly with knee flexion angle throughout the gait cycle. Conversely, Wang et al. (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e) applied 400 N parallel to the femoral shaft and 300 N along the articular alignment load to knee specimens, observing an average 20\u0026deg; external rotation of the femur with 7mm posterior translation during 0\u0026ndash;90\u0026deg; flexion. At 130\u0026deg; flexion, tibial internal rotation and femoral adduction significantly increased, with greater femoral posterior displacement causing the lateral condyle to lift off the tibial surface and contact the posterior horn of the meniscus. In KOA patients, Fukaya et al. (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e) identified stress concentration at the medial meniscal margin in standing posture, inferring that narrowed medial joint space due to KOA leads to degenerative medial osteophyte formation, generating lateral thrust during standing that shifts tibial articular surface loads toward the medial margin.\u003c/p\u003e \u003cp\u003eDuring deep squatting in normal knees, symmetrical von-Mises stress in medial and lateral menisci reflects physiological load balance. Wang et al. (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e) observed nearly equal medial-lateral stresses during 0\u0026ndash;90\u0026deg; flexion, with peak stress at 10 MPa in full extension decreasing to 6 MPa at 90\u0026deg;, whereas at 130\u0026deg; flexion, medial stress exceeded lateral with a peak of 21 MPa, more posteriorly concentrated on the femoral condyle compared to our normal group. This was attributed to increased femoral posterior displacement and lateral condyle lifting off the tibial surface, reducing tibiofemoral contact area and amplifying load-induced stress concentration. The higher peak stress in their study likely resulted from larger flexion angles and inclusion of lower limb alignment loads. In the KOA model, lateral meniscus stress surged to 26.167 MPa, higher than the normal group. We attribute this to two factors: 1) the KOA medial meniscus is thinner than normal, with the pressure center shifting posteriorly during flexion to act on the delicate medial margin, exacerbating stress concentration; 2) observation of tibial medial plateau cartilage stress and medial condyle stress distribution suggests partial medial meniscal dislocation in deep squatting, further reducing contact area and intensifying stress concentration. These findings indicate that alignment abnormalities disrupt joint surface compliance, imposing abnormal shear loads on menisci. The stress in the subchondral cortical bone of the KOA group is 80% higher than that of the normal group, which is associated with the tibial plateau posterior margin bearing the load during deep squatting. In contrast, trabecular bone stress post OW-HTO increased to 8.377 MPa, reflecting increased axial load borne by trabecular bone after osteotomy, contrasting with the cortical bone-dominated loading in standing posture. These differences highlight a more pronounced \"stress amplification effect\" of deep squatting in pathological and post-operative knees, particularly when joint surface integrity is compromised or alignment is altered.\u003c/p\u003e \u003cp\u003eIn patients with KOA, ACL stress was twice as high as in normal subjects, and PCL stress was 2.7 times higher than in the normal group. Such abnormal high stresses are likely caused by reduced joint stability, as the ACL and PCL normally restrict tibial translation relative to the femur in healthy knees. However, in KOA, articular cartilage wear leads to narrowed joint space, varus malalignment, and increased tibial plateau posterior slope, forcing these ligaments to bear greater stress to maintain joint stability. This compensatory mechanism may contribute to ligament damage, Rajgopal et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e) proposed that ACL injury during osteoarthritis progression induces kinematic changes, leading to posterior wear of medial and lateral femoral condyles, that aligns with our observation of elevated medial condyle stress in KOA. Additionally, an MRI imaging study carried out by Biswal et al. (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e) found that ACL tears will result in rapid degradation of the tibial cartilage, with cartilage damage located anteriorly or posteriorly progressing faster than that located centrally, which is the same trend we observed in the distribution of high stress areas in the tibial cartilage of the KOA knee.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Mechanics-related effects of implants in the deep squat condition\u003c/h2\u003e \u003cp\u003eProsthetic failure is one of the catastrophic complications of UKA and OW-HTO (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). Aseptic loosening and periprosthetic fractures account for 36% and 21% of revision cases in knee arthroplasty, respectively, which are closely associated with prosthetic materials, implantation techniques, and mechanical loading (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e). The yield strength of Co-Cr-Mo alloy is about 800\u0026ndash;1000 MPa in previous studies (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e), while the fatigue limit of Ti-6Al-4V in air is 750 MPa, but related studies have found that the fatigue limit decreases to about 450 MPa in a simulated human environment (0.9% NaCl solution) (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). In this study, peak stresses in the UKA tibial component during deep squatting were observed to be 419.17 MPa, whereas femoral component and OW-HTO implant stresses reached 1075.6 MPa and 668.74 MPa, respectively, which basically reached the fatigue limit of each material, and repeated deep squatting may lead to fatigue cracking of the prosthetic component.\u003c/p\u003e \u003cp\u003eStress gradients at the bone implant interface may induce interfacial micromotion, which over time can lead to fatigue fracture of the bone cement. Previous studies indicate that the yield strength of bone cement typically ranges from 30\u0026ndash;50 MPa, with fatigue cracks often originating at the bone-cement interface where crack initiation occurs at stress levels equivalent to 40\u0026ndash;50% percent of its ultimate strength. In physiological environments (0.9% NaCl solution), the fatigue life of bone cement is shorter than in air (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). During deep squatting in this study, stress concentrated at the posterior margin of both femoral and tibial-cement interfaces, exceeding the yield strength of bone cement and posing a high risk of cement fragmentation. On the other hand, trabecular bone, as a porous network structure, has a strength limit closely associated with trabecular density, orientation, and mineral content. Experimental evidence shows that the compressive strength limit of knee trabecular bone ranges from approximately 1.5-8 MPa (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e), in contrast to 100\u0026ndash;200 MPa for cortical bone (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e). While trabecular bone stresses at the bone cement interface in this study remained below these thresholds, the cortical bone stress at the femoral osteotomy interface after UKA reached 344.15 MPa. This \"stress overload\" may induce interfacial micromotion, accelerating interfacial bone resorption and collapse, and ultimately leading to fractures. Such mechanical behavior represents a critical factor contributing to prosthetic loosening after UKA.\u003c/p\u003e \u003cp\u003eDue to the significantly higher Young\u0026rsquo;s modulus of metallic implants compared to human bone tissue, loads are transferred through the prosthesis rather than the surrounding bone, inducing a stress shielding effect. Following implantation, this effect occurs during knee flexion, manifesting as uneven stress distribution at the bone cement layer and osteotomy interface in this study, particularly severe on the tibial side of the UKA group. Stress shielding often leads to osteoporosis and osteolysis, which are closely associated with implant loosening and periprosthetic fractures (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e). In this study, cortical bone stress at the tibial osteotomy surface was most concentrated in full extension, located at the anterior margin of the UKA osteotomy surface and the trabecular bone osteotomy surface of the OW-HTO group. This may activate osteoclast activity, leading to bone resorption at the osteotomy site or delayed nonunion in the hinge region (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Negative effects of deep squatting on knee joint structure\u003c/h2\u003e \u003cp\u003eThe high stress states in menisci and ligaments during deep squatting pose potential threats to post-operative outcomes. Mononen et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e) developed an algorithm based on tissue biomechanics and computational simulation to model KOA progression, in which excessive maximum principal stress drives iterative reduction in collagen network stiffness. Their analysis determined a threshold of 5\u0026ndash;7 MPa for maximum principal stress in collagen fiber degeneration. This study found that maximum principal stresses in menisci of both the normal and KOA groups exceeded this threshold, suggesting a long-term risk for meniscal fibrosis or tears. Daszkiewicz et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e) attributed such differences primarily to increased circumferential stress, demonstrating in their simulations that medial meniscal circumferential stress in the KOA model was 7-fold higher than in healthy knees at 0\u0026deg; knee flexion. Such elevated circumferential stress commonly leads to radial tears in the mid-posterior meniscus and posterior horn injuries. In the OW-HTO group, however, medial ligament stresses in both the arthritic and post OW-HTO states exceeded normal levels, resulting in ineffective medial compartment decompression. Neither maximum von-Mises stress nor maximum principal stress showed significant changes compared to the preoperative KOA state.\u003c/p\u003e \u003cp\u003eCartilage degeneration also signals further progression of KOA. Kerin et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e) measured the compressive strength range of normal adult knee cartilage as 3\u0026ndash;10 MPa through in vitro compression tests. Malekipour et al. (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e) combined impact tests with finite element analysis to propose that microdamage occurs in cartilage-bone complexes when peak stress exceeds 12 MPa. In this study, the distribution trend of maximum principal stress in the KOA knee was generally consistent with that in the normal knee, but the high-stress regions were more extensive. In the post UKA group, replacing the medial compartment restored normal joint space, and load by the prosthesis helped reduce lateral femoral cartilage stress to normal levels.\u003c/p\u003e \u003cp\u003eIn the OW-HTO group, femoral cartilage changes mirrored those in the menisci, which we attribute to insufficient release of the MCL. Van Egmond et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e) demonstrated through OW-HTO modeling that release of the superficial MCL helps reduce medial compartment pressure. Bagherifard et al. (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e) reported via imaging measurements that 30 OW-HTO patients showed a 71.5% average reduction in medial joint space compared to preoperative levels, indicating that appropriate superficial MCL release aids in load transfer from the medial compartment consistent with our observations. However, as critical stabilizers, bone and cartilage tissue exhibit specific stress distributions during deep squatting, which warrants further analysis through full-cycle mechanical simulations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Limitations of the study\u003c/h2\u003e \u003cp\u003eThis time, we only focus on the mechanical situation under the specific condition of 120\u0026deg; squat, and the mechanical change of the dynamic process from standing to squatting is still unclear, and the results can not be extended to illustrate the mechanical state of more angles. Secondly, the setting of each result of the knee joint as isotropic material, as well as the simplified processing of some structures, inevitably differ from the real knee joint state, thus causing errors in the experimental results, and these shortcomings will be improved in further research.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eSquatting significantly increases stress on various structures of the knee joint. UKA reconstructs knee joint load balance by replacing the medial diseased compartment, demonstrating better adaptability for patients with high demands for frequent flexion movements such as squatting. However, the stress on UKA prosthetic components approaches the material fatigue limit, posing risks of aseptic loosening and prosthetic fragmentation. While HTO maximally preserves the original knee joint structure, it exhibits a tendency for accelerated degeneration during squatting, necessitating attention to MCL release during surgery. In future personalized treatment, there should be further integration of patient activity levels, deformity types, and soft tissue status to comprehensively evaluate the biomechanical adaptability of surgical procedures, aiming to achieve better prognoses.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eKOA Knee osteoarthritis\u003c/p\u003e\n\u003cp\u003eUKA Unicompartmental knee arthroplasty\u003c/p\u003e\n\u003cp\u003eHTO High tibial osteotomy\u003c/p\u003e\n\u003cp\u003eOW-HTO Open-wedge HTO\u003c/p\u003e\n\u003cp\u003eFEA Finite element analysis\u003c/p\u003e\n\u003cp\u003eACL Anterior cruciate ligament\u003c/p\u003e\n\u003cp\u003ePCL Posterior cruciate ligament\u003c/p\u003e\n\u003cp\u003eMCL Medial collateral ligament\u003c/p\u003e\n\u003cp\u003eLCL lateral collateral ligament\u003c/p\u003e\n\u003cp\u003eTKA Total knee arthroplasty\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to express our gratitude to all participants for their contributions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConception and design of the study: Z-H Z and Y-S Q; Acquisition of data: Z-H Z, Y-S Q, B-G W, Y-X W; Analyses of data: Z-H Z and B-X M; Drafting the work: Z-H Z and H-R-C B; Revising it critically for important intellectual content: Z Z and Y-S X; All authors approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the National Natural Science Foundation of China (Grant numbers: 82172444, 81960399), the Natural Science Foundation of Inner Mongolia Autonomous Region (2024ZD32), the Science and Technology Plan Project of Inner Mongolia Autonomous Region (2023YFSH0020, 2022YFSH0053, 2021GG0127) and the Science and Technology Plan Project of Wuhai(2023WHSKJJH06).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll relevant data supporting the conclusions are included within the article and tables. The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFrom The Ethics Committee of Inner Mongolia Autonomous Region People\u0026apos;s Hospital approved this study (No. 202507305L). Informed consent Informed consent was obtained from all individual participants included in the study. All methods were performed in accordance with the guidelines and regulations of the Ethics Committee of Inner Mongolia Autonomous Region People\u0026apos;s Hospital. Our study adhered to the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor details\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eOrthopedic Center (Sports Medicine Center), Inner Mongolia Autonomous Region People\u0026apos;s Hospital, Hohhot, 010017, China\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e2\u003c/sup\u003eThe People\u0026apos;s Hospital of Wu Hai Inner Mongolia, Wuhai, 016000, China\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eJahn J, Ehlen QT, Huang CY. Finding the Goldilocks Zone of Mechanical Loading: A Comprehensive Review of Mechanical Loading in the Prevention and Treatment of Knee Osteoarthritis. Bioengineering (Basel). 2024;11(2).\u003c/li\u003e\n\u003cli\u003eSchoenfeld BJ. Squatting kinematics and kinetics and their application to exercise performance. J Strength Cond Res. 2010;24(12):3497-506.\u003c/li\u003e\n\u003cli\u003eCooper C, McAlindon T, Coggon D, Egger P, Dieppe P. Occupational activity and osteoarthritis of the knee. Ann Rheum Dis. 1994;53(2):90-3.\u003c/li\u003e\n\u003cli\u003eHartmann H, Wirth K, Klusemann M. Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load. Sports Med. 2013;43(10):993-1008.\u003c/li\u003e\n\u003cli\u003eMulholland SJ, Wyss UP. Activities of daily living in non-Western cultures: range of motion requirements for hip and knee joint implants. Int J Rehabil Res. 2001;24(3):191-8.\u003c/li\u003e\n\u003cli\u003eCao Z, Mai X, Wang J, Feng E, Huang Y. Unicompartmental Knee Arthroplasty vs High Tibial Osteotomy for Knee Osteoarthritis: A Systematic Review and Meta-Analysis. J Arthroplasty. 2018;33(3):952-9.\u003c/li\u003e\n\u003cli\u003eDebopadhaya S, Acosta E, Ortiz D, 3rd. Trends and outcomes in the surgical management of young adults with knee osteoarthritis using high tibial osteotomy and unicompartmental knee arthroplasty. Arch Orthop Trauma Surg. 2024;144(9):3995-4002.\u003c/li\u003e\n\u003cli\u003eKoh IJ, Kim MS, Sohn S, Song KY, Choi NY, Jung H, In Y. Predictive factors for satisfaction after contemporary unicompartmental knee arthroplasty and high tibial osteotomy in isolated medial femorotibial osteoarthritis. Orthop Traumatol Surg Res. 2019;105(1):77-83.\u003c/li\u003e\n\u003cli\u003ePing H, Wen J, Liu Y, Li H, Wang X, Kong X, Chai W. Unicompartmental knee arthroplasty is associated with lower pain levels but inferior range of motion, compared with high tibial osteotomy: a systematic overview of meta-analyses. J Orthop Surg Res. 2022;17(1):425.\u003c/li\u003e\n\u003cli\u003eKothurkar R, Lekurwale R. Techniques to determine knee joint contact forces during squatting: A systematic review. Proc Inst Mech Eng H. 2022;236(6):775-84.\u003c/li\u003e\n\u003cli\u003eHale R, Green J, Hausselle J, Saxby D, Gonzalez RV. Quantified in vitro tibiofemoral contact during bodyweight back squats. J Biomech. 2018;79:21-30.\u003c/li\u003e\n\u003cli\u003eChurchill DL, Incavo SJ, Johnson CC, Beynnon BD. The influence of femoral rollback on patellofemoral contact loads in total knee arthroplasty. J Arthroplasty. 2001;16(7):909-18.\u003c/li\u003e\n\u003cli\u003eWunschel M, Leichtle U, Obloh C, Wulker N, Muller O. The effect of different quadriceps loading patterns on tibiofemoral joint kinematics and patellofemoral contact pressure during simulated partial weight-bearing knee flexion. Knee Surg Sports Traumatol Arthrosc. 2011;19(7):1099-106.\u003c/li\u003e\n\u003cli\u003eShu J, Zheng N, Teng H, Tsai TY, Liu Z. In vivo biomechanical dynamic simulation of a healthy knee during the single-leg lunge and its experiment validation. Med Eng Phys. 2024;129:104183.\u003c/li\u003e\n\u003cli\u003ePfeiffer FM. The Use of Finite Element Analysis to Enhance Research and Clinical Practice in Orthopedics. J Knee Surg. 2016;29(2):149-58.\u003c/li\u003e\n\u003cli\u003eZhang ZH, Qi YS, Wei BG, Bao HR, Xu YS. Application strategy of finite element analysis in artificial knee arthroplasty. Front Bioeng Biotechnol. 2023;11:1127289.\u003c/li\u003e\n\u003cli\u003eKang KT, Son J, Suh DS, Kwon SK, Kwon OR, Koh YG. Patient-specific medial unicompartmental knee arthroplasty has a greater protective effect on articular cartilage in the lateral compartment: A Finite Element Analysis. Bone Joint Res. 2018;7(1):20-7.\u003c/li\u003e\n\u003cli\u003eWen PF, Guo WS, Gao FQ, Zhang QD, Yue JA, Cheng LM, Zhu GD. Effects of Lower Limb Alignment and Tibial Component Inclination on the Biomechanics of Lateral Compartment in Unicompartmental Knee Arthroplasty. Chin Med J (Engl). 2017;130(21):2563-8.\u003c/li\u003e\n\u003cli\u003ePan CS, Wang X, Ding LZ, Zhu XP, Xu WF, Huang LX. The best position of bone grafts in the medial open-wedge high tibial osteotomy: A finite element analysis. Comput Methods Programs Biomed. 2023;228:107253.\u003c/li\u003e\n\u003cli\u003eArmillotta N, Bori E, Innocenti B. Finite element analysis of malposition in bi-unicompartmental knee arthroplasty. Arch Orthop Trauma Surg. 2023;143(6):3447-55.\u003c/li\u003e\n\u003cli\u003eGeeslin AG, Civitarese D, Turnbull TL, Dornan GJ, Fuso FA, LaPrade RF. Influence of lateral meniscal posterior root avulsions and the meniscofemoral ligaments on tibiofemoral contact mechanics. Knee Surg Sports Traumatol Arthrosc. 2016;24(5):1469-77.\u003c/li\u003e\n\u003cli\u003eBao HR, Zhu D, Gong H, Gu GS. The effect of complete radial lateral meniscus posterior root tear on the knee contact mechanics: a finite element analysis. J Orthop Sci. 2013;18(2):256-63.\u003c/li\u003e\n\u003cli\u003eMitani T, Inoue K, Takahashi S. Relationship between joint angle and contact force at the knee during normal gait. J Adv Mech Des Syst Manuf. 2025;19(2):9.\u003c/li\u003e\n\u003cli\u003eWang J, Tao K, Li H, Wang C. Modelling and analysis on biomechanical dynamic characteristics of knee flexion movement under squatting. ScientificWorldJournal. 2014;2014:321080.\u003c/li\u003e\n\u003cli\u003eFukaya T, Mutsuzaki H, Aoyama T, Watanabe K, Mori K. A Simulation Case Study of Knee Joint Compressive Stress during the Stance Phase in Severe Knee Osteoarthritis Using Finite Element Method. Medicina (Kaunas). 2021;57(6).\u003c/li\u003e\n\u003cli\u003eRajgopal A, Noble PC, Vasdev A, Ismaily SK, Sawant A, Dahiya V. Wear Patterns in Knee Articular Surfaces in Varus Deformity. J Arthroplasty. 2015;30(11):2012-6.\u003c/li\u003e\n\u003cli\u003eBiswal S, Hastie T, Andriacchi TP, Bergman GA, Dillingham MF, Lang P. Risk factors for progressive cartilage loss in the knee: a longitudinal magnetic resonance imaging study in forty-three patients. Arthritis Rheum. 2002;46(11):2884-92.\u003c/li\u003e\n\u003cli\u003eFisher CR, Patel R. Profiling the Immune Response to Periprosthetic Joint Infection and Non-Infectious Arthroplasty Failure. Antibiotics (Basel). 2023;12(2).\u003c/li\u003e\n\u003cli\u003eKim S, Baril C, Rudraraju S, Ploeg HL. Influence of Porosity on Fracture Toughness and Fracture Behavior of Antibiotic-Loaded PMMA Bone Cement. J Biomech Eng. 2022;144(1).\u003c/li\u003e\n\u003cli\u003eZeng L, Xiang N, Wei B. A COMPARISON OF CORROSION RESISTANCE OF COBALT-CHROMIUM-MOLYBDENUM METAL CERAMIC ALLOY FABRICATED WITH SELECTIVE LASER MELTING AND TRADITIONAL PROCESSING. Journal of Prosthetic Dentistry. 2014;112(5):1217-24.\u003c/li\u003e\n\u003cli\u003edos Santos SV, Lima GD, Santos RCS, Nascimento BL, Griza S. Fatigue and Corrosion Fatigue of Thermally Oxidized Ti6Al4V Alloy. J Mater Eng Perform. 2024:8.\u003c/li\u003e\n\u003cli\u003eRoemhildt ML, McGee TD, Wagner SD. Novel calcium phosphate composite bone cement: strength and bonding properties. J Mater Sci Mater Med. 2003;14(2):137-41.\u003c/li\u003e\n\u003cli\u003eDunne NJ, Orr JF, Mushipe MT, Eveleigh RJ. The relationship between porosity and fatigue characteristics of bone cements. Biomaterials. 2003;24(2):239-45.\u003c/li\u003e\n\u003cli\u003eHvid I. Mechanical strength of trabecular bone at the knee. Dan Med Bull. 1988;35(4):345-65.\u003c/li\u003e\n\u003cli\u003eWachter NJ, Krischak GD, Mentzel M, Sarkar MR, Ebinger T, Kinzl L, et al. Correlation of bone mineral density with strength and microstructural parameters of cortical bone in vitro. Bone. 2002;31(1):90-5.\u003c/li\u003e\n\u003cli\u003eBori E, Armaroli F, Innocenti B. Biomechanical analysis of femoral stems in hinged total knee arthroplasty in physiological and osteoporotic bone. Comput Methods Programs Biomed. 2022;213:106499.\u003c/li\u003e\n\u003cli\u003eGalas A, Banci L, Innocenti B. The Effects of Different Femoral Component Materials on Bone and Implant Response in Total Knee Arthroplasty: A Finite Element Analysis. Materials (Basel). 2023;16(16).\u003c/li\u003e\n\u003cli\u003eMononen ME, Tanska P, Isaksson H, Korhonen RK. A Novel Method to Simulate the Progression of Collagen Degeneration of Cartilage in the Knee: Data from the Osteoarthritis Initiative. Sci Rep. 2016;6:21415.\u003c/li\u003e\n\u003cli\u003eDaszkiewicz K, Luczkiewicz P. Biomechanics of the medial meniscus in the osteoarthritic knee joint. PeerJ. 2021;9:e12509.\u003c/li\u003e\n\u003cli\u003eKerin AJ, Wisnom MR, Adams MA. The compressive strength of articular cartilage. Proc Inst Mech Eng H. 1998;212(4):273-80.\u003c/li\u003e\n\u003cli\u003eMalekipour F, Oetomo D, Lee PV. Equine subchondral bone failure threshold under impact compression applied through articular cartilage. J Biomech. 2016;49(10):2053-9.\u003c/li\u003e\n\u003cli\u003evan Egmond N, Hannink G, Janssen D, Vrancken AC, Verdonschot N, van Kampen A. Relaxation of the MCL after an Open-Wedge High Tibial Osteotomy results in decreasing contact pressures of the knee over time. Knee Surg Sports Traumatol Arthrosc. 2017;25(3):800-7.\u003c/li\u003e\n\u003cli\u003eBagherifard A, Jabalameli M, Mirzaei A, Khodabandeh A, Abedi M, Yahyazadeh H. Retaining the medial collateral ligament in high tibial medial open-wedge osteotomy mostly results in post-operative intra-articular gap reduction. Knee Surg Sports Traumatol Arthrosc. 2020;28(5):1388-93.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Knee osteoarthritis, Unicompartmental knee arthroplasty, High tibial osteotomy, Squatting, Finite element analysis","lastPublishedDoi":"10.21203/rs.3.rs-6740482/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6740482/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective: \u003c/strong\u003eKnee osteoarthritis (KOA) often necessitates surgical interventions like unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO), but their biomechanical responses during deep squatting. This three-dimensional finite element analysis (FEA) aimed to compare the mechanical behaviors of knees treated with UKA and open-wedge HTO (OW-HTO) during 120° squatting, providing insights for postoperative mechanical evaluations and patient management.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eLaser 3D scanning/MRI/CT data were used to construct 3D finite element models of the healthy knee, KOA knee, UKA knee and OW-HTO knee in 120° flexion conditions, and mechanical loads in the deep squat condition were applied to assess the stresses on the meniscus, cartilage, bone, ligaments, and implants under deep squat conditions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eThe results showed that in the normal knee during deep squatting, the menisci had a symmetrical stress distribution. In KOA knees, there were significant stress increases and concentrations in the menisci, cartilage, and subchondral bone. UKA effectively reduced lateral meniscus stress, lateral femoral cartilage stress, and ligament stresses, restoring a more normal mechanical environment. In contrast, OW-HTO knees still had high meniscal, cartilage, and bone stresses, similar to the KOA state. The maximum stresses in the implants of both UKA and OW-HTO approached the fatigue limits of their materials, and high stresses at the bone-implant interfaces might lead to complications such as aseptic loosening.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eThis study tentatively suggests that UKA is suitable for patients with high-frequency flexion demands, but there is a risk of aseptic loosening and fragmentation of the prosthesis, whereas HTO is suitable for young, well-boned patients with predominantly extra-articular deformities. Regardless of the procedure, prolonged knee flexion at large angles should be avoided to improve the prognosis.\u003c/p\u003e","manuscriptTitle":"Knee biomechanics in the deep squatting state after unicompartmental knee arthroplasty versus high tibial osteotomy: A 3-dimensional finite element study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-20 15:27:04","doi":"10.21203/rs.3.rs-6740482/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ab33efc4-07df-48d1-a357-ae1fd7dd8a49","owner":[],"postedDate":"June 20th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-08-08T14:23:57+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-20 15:27:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6740482","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6740482","identity":"rs-6740482","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}