Comparison of Functional and Mechanical Alignment in Posterior-Stabilized Total Knee Arthroplasty: A Propensity-Matched Retrospective Cohort Study

Comparison of Functional and Mechanical Alignment in Posterior-Stabilized Total Knee Arthroplasty: A Propensity-Matched Retrospective Cohort 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 Comparison of Functional and Mechanical Alignment in Posterior-Stabilized Total Knee Arthroplasty: A Propensity-Matched Retrospective Cohort Study Pierre-Alban Bouche, Halah Kutaish, Toscan Donat, William Digiovanni, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9226681/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 Background: While mechanical alignment (MA) has long been the gold standard in total knee arthroplasty (TKA), functional alignment (FA) has recently emerged as a promising alternative, particularly with the advent of robotic-assisted techniques. The present study aims to compare MA and FA in terms of pain, functional outcomes, and perioperative outcomes. Methods: This single-center, retrospective cohort study included 172 patients undergoing primary TKA performed by the same surgeon between 2016 and 2024. Following a 1:1 propensity score matching, patients receiving MA-TKA with navigation (n = 86) were compared with those receiving FA-TKA with robotic assistance (n = 86). The primary outcome was the rate of chronic pain (VAS ≥ 4/10) at six months. Secondary outcomes included validated patient-reported outcomes (PROs: OKS, SF-12, WOMAC, FJS, SKV), Net Promoter Score (NPS), operative time, hospital stay, and complications. Results: At six months, the prevalence of chronic pain was comparable between groups (MA: 15.1%, FA: 19.8%; p = 0.55). At one-year, PROs were similar across all metrics (p > 0.05), although the FA group consistently demonstrated numerically superior scores. Two individual WOMAC items favored the FA group (pain and difficulty walking on flat surfaces; both p = 0.02). Operative time (101.7 ± 16.7 vs 119.6 ± 16.0 min; p < 0.01) and hospital stay (7.7 ± 2.0 vs 9.2 ± 3.8 days; p < 0.01) were significantly shorter in the FA group. Complication and revision rates were low and not significantly different between groups. Conclusion: Functional alignment in robotic-assisted TKA results in comparable pain and functional outcomes to mechanical alignment, while also demonstrating shorter operative time and hospital stay. These findings support the safety and clinical application of individualized alignment strategies in contemporary TKA. Level of evidence IV, retrospective cohort Functional alignment Robotic TKA PROMs TKA Figures Figure 1 Figure 2 Figure 3 Introduction Total knee arthroplasty (TKA) is one of the most frequently performed surgical procedures worldwide 1 , 2 . Moreover TKA demand is projected to increase substantially in the coming years due to aging populations and the rising prevalence of degenerative joint disease 3 , 4 . Despite the overall success of TKA, an estimated 10% to 20% of patients remain dissatisfied after the operation 5 . This dissatisfaction underscores the importance of optimizing long-term outcomes and tailoring surgical techniques to patient-specific anatomy and function. Malalignment of prosthetic components can adversely affect functional outcomes and implant longevity, leading to accelerated polyethylene wear and early implant loosening 6 – 10 . Historically, alignment strategies have relied on the principle of mechanical alignment (MA), which aims to restore a neutral coronal alignment between the hip, knee, and ankle. A mechanical axis within ± 3° of neutral varus or valgus has traditionally been associated with improved implant survival 8 , 11 , 12 . However, the reconstructed neutral mechanical axis, perpendicular to the joint line, often diverges from the native anatomical and kinematic characteristics of the knee. This mismatch has been identified as a potential contributor to patient dissatisfaction 9 , 12 – 14 , particularly when it results in unintended alterations to joint line obliquity or imbalances in medial-lateral soft tissue tension—factors not addressed by the mechanical alignment philosophy. As such, alternative alignment strategies have since emerged. Kinematic alignment (KA), initially proposed by Howell et al. 13,14 , seeks to restore the patient’s pre-arthritic joint line and limb orientation by matching the thickness of the resected bone and cartilage with that of the prosthetic components, thereby preserving the native orientation and kinematics of the knee. Despite deviating from the neutral mechanical axis, KA has not been associated with increased implant failure in mid-term studies, and the relationship between mechanical axis alignment within ± 3° and implant survivorship remains unconfirmed 13 , 15 . However, no conclusive evidence to date has demonstrated the superiority of KA over MA in terms of functional outcomes 16 . More recently, the adoption of robotic-assisted TKA has enabled the implementation of functional alignment (FA) 17 . Functional alignment aims to achieve a balanced knee in both extension and flexion by reproducing the patient’s native anatomy and soft tissue envelope. Robotic systems allow for real-time intraoperative assessment of knee alignment, bone resection, ligament balance, and joint space symmetry, facilitating individualized implant positioning that aims to restore native knee kinematics while compensating for arthritic changes 18 – 20 . Although functional alignment is increasingly adopted in clinical practice, comparative data with traditional mechanical alignment remains limited, especially for postero-stabilized (PS) TKA 21 . The present study means to compare mechanical and functional alignment in TKA in terms of patient-reported and functional outcomes at a minimum of one year follow-up. By evaluating these two alignment philosophies in a modern, technologically enhanced surgical setting, we aim to provide further evidence to guide surgical decision-making and improve patient satisfaction following TKA. Methods The Cantonal Commission for Research Ethics of Geneva (N°: 2024 − 01604) approved this single-center, retrospective study of prospectively collected data in accordance with the Declaration of Helsinki. All patients were informed about the study. All patients have given their consent. Patients This retrospective cohort study included all patients who underwent primary TKA for osteoarthritis between January 2016 and April 2024 and received a cemented posterior-stabilized Persona total knee arthroplasty (Zimmer Biomet) by the same senior orthopedic surgeon. Between 2016 and 2019, 118 patients received MA TKA using a navigation system (OrthoKey, Zimmer). From 2019 to April 2024, 199 patients underwent FA TKA with robotic assistance (ROSA system, Zimmer). After propensity score matching, 172 patients remained for final analysis, with 86 in each group (Fig. 1). The overall cohort had a mean age of 72.0 ± 7.9 years (range: 56–91), and 68.6% were women (118/172). Mean body mass index (BMI) was 28.6 ± 5.7 kg/m² (range: 18.3–43.6). Preoperative alignment analysis showed a mean hip-knee-ankle (HKA) angle of 177.7° ± 7.9° (range: 153–195°), a mean lateral distal femoral angle (LDFA) of 88.0° ± 3.0° (range: 78–98°), and a mean medial tibial plateau angle (MTPA) of 87.3° ± 4.0° (range: 74–97°). Based on coronal alignment, 60.5% (101/167) of knees were classified as varus and 39.5% (66/167) as valgus. According to the CPAK classification, the distribution was as follows: Type I, 15.5% (25/167); Type II, 23.0% (37/167); Type III, 24.8% (40/167); Type IV, 11.2% (18/167); Type V, 14.9% (24/167); Type VI, 7.5% (12/167); Type VII, 2.5% (4/167); Type VIII, 0.0% (0/167); and Type IX, 0.6% (1/167). Mean follow-up duration was 4.3 ± 2.1 years, with a significant difference between the MA group (5.8 ± 1.7 years) and the FA group (2.9 ± 0.9 years) (p < 0.01). Demographic and baseline characteristics for both groups are detailed in Table 1 . Table 1 Variables N Mechanical aligment Functional alignment p-value Age (years) 86 72.6 (8.3) 86 71.4 (7.6) 0.47 Gender man 27 31.4% 27 31.4% 1.0 woman 59 68.6% 59 68.6% BMI 86 28.5(5.9) 86 28.6(5.4) 0.94 ASA score 86 2.4(0.5) 86 2.3(0.5) 0.4 Side Left 36 41.9% 36 41.9% 1.0 Right 50 58.1% 50 58.1% HKA preop(°) 86 178.9 (8.3) 84 176.5(7.5) 0.05 Deformity Varus 43 51.8% 58 69.0% 0.03 Valgus 40 48.2% 26 31.0% LDFA preop(°) 43 87.7(2.3) 48 88.1(3.0) 0.50 MPTA preop(°) 43 87.5(3.9) 48 85.9(3.5) 0.03 CPAK preop I 15 19.2% 10 12.0% 0.77 II 16 20.5% 21 25.3% III 18 23.1% 22 26.5% IV 9 11.5% 9 10.8% V 13 16.7% 11 13.3% VI 5 6.4% 7 8.4% VII 1 1.3% 3 3.6% VIII 0 0.0% 0 0.0% IX 1 1.3% 0 0.0% Surgical Data All procedures were performed using a medial parapatellar approach without a tourniquet, with cemented PS implants and patellar resurfacing. The alignment strategy differed between groups. In the mechanical alignment group, the objective was to restore a neutral mechanical axis (± 3°), targeting an MPTA and LDFA of 90° (± 3°). The functional alignment group instead utilized individualized bone resections to recreate each patient’s native anatomy and knee kinematics by balancing the medial and lateral collateral ligaments in both flexion and extension. The detailed parameters and boundaries defining the functional alignment strategy are presented in Table 2 . Intraoperative collateral ligament tension was assessed using the ROSA software and quantified as medial and lateral joint line openings (in millimeters). In the functional alignment group, intraoperative data were available for 68 of the 86 patients. Based on the criteria defined in Table 2 , 91% of TKAs (62/68) were considered balanced in extension, with a mean medial–lateral gap difference of − 0.28 ± 1.1 mm. In flexion, 100% (68/68) were balanced, with a mean medial-lateral difference of − 0.92 ± 1.7 mm. As defined by the flexion-extension gap difference, 85.3% (58/68) were balanced medially, with a mean delta of − 0.08 ± 1.7 mm. Surgical technique, perioperative management, and rehabilitation protocols remained consistent throughout the study period. All patients followed an identical postoperative rehabilitation program, which included early full weight-bearing and mobilization using two crutches beginning the day after surgery. Variables/ Outcomes Demographic data including age, sex, BMI, and American Society of Anesthesiologists (ASA) physical status classification were collected for each patient on the day of surgery. Clinical follow-up data were recorded during hospitalization and at one year postoperatively. Functional outcomes included the following validated scores: Visual Analogue Scale (VAS) for pain, Oxford Knee Score (OKS), SF-12 (physical and mental components), Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain and function subscales, the Simple Knee Value (SKV), the Forgotten Joint Score (FJS), and the Net Promoter Score (NPS). For the WOMAC and FJS, individual item analysis was also performed. Data on surgical complications were collected, as well as data on surgical revision and reoperation. Operative time and length of hospital stay were also recorded. The primary outcome was the proportion of patients experiencing moderate to severe pain (defined as VAS ≥ 4/10, referred to as chronic pain 22 ) after 6 months postoperatively. Secondary outcomes included comparisons between groups for pain and functional scores, length of hospital stay, operative time, and complication rates at 1-year follow-up. Statistical Analysis A total of 70 patients per group was estimated to be necessary to detect a 1.0-point difference in pain scores between groups, assuming a standard deviation of 2.0, with a two-sided alpha level of 0.05 and 80% statistical power. To ensure comparability between groups and reduce the influence of confounding factors and selection bias, a propensity score matching approach was applied. The propensity score incorporated age at surgery, sex, and BMI. Patients in the MA group were matched 1:1 to those in the FA group using a logit model with a caliper width of 0.05. Categorical variables are presented as counts and percentages, whereas continuous variables are expressed as means with standard deviations. Group comparisons were performed using Fisher’s exact test for categorical variables and the Wilcoxon rank-sum test for continuous variables. A p-value ≤ 0.05 was considered statistically significant. All analyses were conducted using R software (version 3.5.0; https://www.r-project.org/ ). Results Pain outcomes At six months postoperatively, the mean VAS pain score was 1.5 ± 2.38 (range: 0–10) in the MA group and 1.4 ± 2.20 (range: 0–8) in the FA group, with no statistically significant difference between groups (p = 0.69, Fig. 2). The proportion of patients reporting chronic pain was 17.4% (30/172), with no significant difference between the MA (15.1%, 13/86) and FA groups (19.8%, 17/86; p = 0.55, Fig. 2). Clinical outcomes Baseline preoperative scores were comparable between the two groups (Table 3). At one year postoperatively, no statistically significant differences were observed between the MA and FA groups across all clinical outcome measures, including SF-12 mental and physical scores, WOMAC pain and function subscales, OKS function and pain subscales, FJS, and SKV (all p > 0.05, Table 3). Although none of these differences reached statistical significance, the FA group consistently demonstrated numerically higher scores across several domains, including the SF-12 (mental and physical), WOMAC pain, OKS (total and subscales), and SKV. Changes from baseline to one year are also detailed in Table 3 and did not differ significantly between groups. Analysis of individual WOMAC items revealed two statistically significant differences favoring the FA group. For the items “Pain while walking on a flat surface” and “Difficulty walking on a flat surface,” a greater proportion of patients in the FA group reported no pain (64.7% vs 49.3%; p = 0.02) and no difficulty (64.7% vs 52.9%; p = 0.02), respectively (Fig. 3). No significant differences were found in individual FJS items. Patient satisfaction, assessed by the NPS, was comparable between groups. The proportion of promoter patients (NPS > 8/10) was similar (MA: 85.5% vs FA: 84.6%; p > 0.90), as was the proportion of detractor patients (NPS < 7/10; MA: 8.1% vs FA: 4.6%; p = 0.49). Perioperative Outcomes and Complications Mmean hospital stay was significantly shorter in the FA group compared to the MA group (7.7 ± 2.0 vs 9.2 ± 3.8 days; p < 0.01). Similarly, the mean operative time was significantly lower in the FA group (101.7 ± 16.7 vs 119.6 ± 16.0 minutes; p < 0.01). There were no significant differences between groups regarding early complications or revision rates. The overall complication rate was 7.0% (6/86) in the MA group—comprising three cases of postoperative stiffness, one hematoma, one debridement for a hematogenous infection and one case of persistent pain—compared to 4.7% (4/86) in the FA group, which included one traumatic open joint injury, one superficial infection at the pins sites, one hematoma, and one medial collateral ligament injury (p = 0.75). The overall revision rate remained low in both groups: 1.2% (1/86) in the MA group (one aseptic loosening) and 0.0% (0/86) in the FA group (p = 1.00). Discussion This study demonstrates that at one-year follow-up, no statistically significant differences were observed between MA and FA in terms of postoperative pain, global functional outcomes, or patient satisfaction following TKA with PS implants. However, patients in the FA group exhibited slightly higher, albeit non-significant, scores in several functional and quality-of-life domains, suggesting a potentially favorable trend toward this alignment strategy. These findings raise the question of the sensitivity of global scores in detecting clinically meaningful differences. To our knowledge, this is the first study to compare MA and FA with respect to PROs in a homogeneous cohort receiving the same posterior-stabilized implant. Our observations align with recent literature. Several comparative studies between MA and FA have reported minimal or no differences in global pain and function scores 17 , 21 , 23 – 26 , though a trend favoring FA is often observed without always reaching statistical significance. Lee et al. 25 compared 70 robot-assisted MA, 70 conventional MA, and 70 robot-assisted FA patients and reported significantly better functional outcomes at 6 and 12 months in the FA group. Similarly, Gustke et al. 21 compared 140 FA and 70 MA patients (PS and CS implants) and reported a higher FJS in the FA group (66.3 ± 26.2 vs 60.4 ± 29.2; p = 0.155), as well as significantly greater maximal flexion (125.4° ± 12.5° vs 120.9° ± 7.2°; p < 0.001). In a randomized trial, Young et al. 26 compared 121 MA and 123 FA cases (CR TKA) and observed significant differences favoring FA in the KOOS symptoms subscale (86.6 ± 12.9 vs 82.5 ± 14.0; p = 0.01) and quality of life subscale (76.4 ± 21.7 vs 64.2 ± 19.2; p = 0.02). In our cohort, a detailed analysis of individual WOMAC items revealed statistically significant differences favoring FA in certain domains: a higher proportion of patients reported being pain-free (64.7% vs 49.3%; p = 0.02) and experienced less difficulty walking on a flat surface (64.7% vs 52.9%; p = 0.02). These results highlight the complexity of functional evaluation after TKA and underscore the limitations of global scores in capturing the nuances of patient-perceived recovery. Specifically, ceiling or floor effects may mask subtle but clinically meaningful benefits in specific subpopulations. A more focused approach targeting specific subdomains of function or quality of life may better capture the potential advantages of personalized alignment strategies. Furthermore, other pathophysiological mechanisms may help explain the functional benefits observed with FA. In a randomized trial comparing 29 FA to 31 MA patients with CR implants, Manara et al. 17 found no significant differences in PROMs but reported a higher incidence of medial pivot kinematics in the FA group (58.6% vs 19.4% in MA). This kinematic pattern was associated with improved PROMs compared to symmetrical rollback or lateral pivot patterns, possibly because medial pivot enhances quadriceps mechanics and patellar tracking. This observation may help explain the superior performance of FA patients in our study regarding flat-surface walking in the WOMAC score. In this group, the mean medial-lateral gap difference was − 0.28 ± 1.1 mm in extension, − 0.92 ± 1.7 mm in flexion, and the mean flexion-extension gap difference for the medial compartment was − 0.08 ± 1.7 mm. Preservation of key ligaments and restoration of the native joint line likely contribute to this stability and superior function following FA-TKA. Finally, Yang et al. 27 showed that FA improved joint line parallelism to the floor and resulted in more neutral weight-bearing alignment on gait analysis, compared to MA. These biomechanical parameters may also contribute to the better functional tolerance of FA in certain daily activities. Another notable finding was that hospital stay was shorter in the FA group compared to the MA group (7.7 ± 2.0 vs 9.2 ± 3.8 days; p < 0.01). This difference is likely related to the use of different technologies in the MA and the FA groups. Recent research indicates that the early inflammatory response after robotic surgery is reduced, resulting in decreased postoperative pain during the initial days and facilitating earlier discharge 28 , 29 . Furthermore, robotic placement of cutting guides and accurate bone cuts save time once the learning curve has been surpassed 30 . The current study has several limitations. First, this research is a retrospecitve cohort study based on a prospective institutional arthroplasty registry,not a randomized controlled trial. However, comparable groups were obtained for age, sex, and BMI through propensity score matching. Second, the follow-up duration is relatively short at oneyear. Nevertheless, a recent study by Spece et al. 31 suggests that long-term PROMs beyond one or two years are often incomplete and lose sensitivity over time. Third, different technologies were used between groups: navigation in the MA group and robotic surgery in the FA group. However, no study to date has demonstrated a difference in functional outcomes between these two cutting guide technologies 32 – 34 . Conclusion At one-year follow-up, functional alignment demonstrated comparable outcomes to mechanical alignment in global PROs, pain, and patient satisfaction after posterior-stabilized total knee arthroplasty. However, the FA group exhibited favorable trends and significant improvements in selected functional items, suggesting potential clinical benefits that may not be fully captured by composite scores. These findings support growing interest in personalized alignment strategies and highlight the importance of using more sensitive, domain-specific measures when evaluating patient outcomes after TKA. Abbreviations ASA American Society of Anesthesiologists BMI Body Mass Index CR Cruciate retaining CS Cruciate sacrificing FA Functional Alignment FJS Forgotten Joint Score HKA Hip Knee Ankle angle JLO Joint Line Obliquity LDFA Lateral Distal Femur angle OKS Oxford Knee Score MA Mechanical alignment MPTA Medial Proximal Tibial Angle NPS Net Promoter Score PS Postero stabilized SKV Simple Knee Value TKA Total Knee Arthroplasty VAS Visual Analogue Scale WOMAC Western Ontario and McMaster Universities Arthritis Index Declarations Funding: The researchers did not receive any funding to conduct this study. Ethical approval: This study was approved by the local ethics committee under the N°: 2024-01604. Informed consent: All patients were informed about the study. All patients have given their consent. Declaration of AI Usage: none Consent for publication: Consent for publication: All authors have read and approved the manuscript and consent to its publication. References Blom AW, Donovan RL, Beswick AD, Whitehouse MR, Kunutsor SK. Common elective orthopaedic procedures and their clinical effectiveness: umbrella review of level 1 evidence. BMJ 2021;374:n1511. Bouché P-A, Kutaish H, Gasparutto X, Lubbeke A, Miozzari HH, Hannouche D. Coronal Plane Alignment of the Knee Classification in Osteoarthritic Knees: Poor to Moderate Reliability and Implications for Imaging Choice. The Journal of Arthroplasty 2026;41(3):725–32. Carr AJ, Robertsson O, Graves S, Price AJ, Arden NK, Judge A, et al. Knee replacement. Lancet (London, England) 2012;379(9823):1331–40. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. The Journal of Bone and Joint Surgery American Volume 2007;89(4):780–85. DeFrance MJ, Scuderi GR. Are 20% of Patients Actually Dissatisfied Following Total Knee Arthroplasty? A Systematic Review of the Literature. The Journal of Arthroplasty 2023;38(3):594–99. Schroer WC, Berend KR, Lombardi AV, Barnes CL, Bolognesi MP, Berend ME, et al. Why are total knees failing today? Etiology of total knee revision in 2010 and 2011. The Journal of Arthroplasty 2013;28(8 Suppl):116–19. Mason JB, Fehring TK, Estok R, Banel D, Fahrbach K. Meta-analysis of alignment outcomes in computer-assisted total knee arthroplasty surgery. The Journal of Arthroplasty 2007;22(8):1097–1106. Jeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. The Journal of Bone and Joint Surgery British Volume 1991;73(5):709–14. Bargren JH, Blaha JD, Freeman MA. Alignment in total knee arthroplasty. Correlated biomechanical and clinical observations. Clinical Orthopaedics and Related Research 1983;(173):178–83. Longstaff LM, Sloan K, Stamp N, Scaddan M, Beaver R. Good alignment after total knee arthroplasty leads to faster rehabilitation and better function. The Journal of Arthroplasty 2009;24(4):570–78. Rivière C, Iranpour F, Auvinet E, Howell S, Vendittoli P-A, Cobb J, et al. Alignment options for total knee arthroplasty: A systematic review. Orthopaedics & traumatology, surgery & research: OTSR 2017;103(7):1047–56. Oussedik S, Abdel MP, Victor J, Pagnano MW, Haddad FS. Alignment in total knee arthroplasty. The Bone & Joint Journal 2020;102-B(3):276–79. Howell SM, Howell SJ, Kuznik KT, Cohen J, Hull ML. Does a kinematically aligned total knee arthroplasty restore function without failure regardless of alignment category? Clinical Orthopaedics and Related Research 2013;471(3):1000–1007. Lee YS, Howell SM, Won Y-Y, Lee O-S, Lee SH, Vahedi H, et al. Kinematic alignment is a possible alternative to mechanical alignment in total knee arthroplasty. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA 2017;25(11):3467–79. Parratte S, Pagnano MW, Trousdale RT, Berry DJ. Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern, cemented total knee replacements. The Journal of Bone and Joint Surgery American Volume 2010;92(12):2143–49. Gibbons JP, Zeng N, Bayan A, Walker ML, Farrington B, Young SW. No Difference in 10-year Clinical or Radiographic Outcomes Between Kinematic and Mechanical Alignment in TKA: A Randomized Trial. Clinical Orthopaedics and Related Research 2025;483(1):140–49. Manara JR, Steer R, Whitehouse SL, Collopy D, Clark GW. Functional alignment restores native kinematics more consistently than mechanical axis alignment in total knee arthroplasty. The Bone & Joint Journal 2025;107-B(4):423–31. Desai AS, Dramis A, Kendoff D, Board TN. Critical review of the current practice for computer-assisted navigation in total knee replacement surgery: cost-effectiveness and clinical outcome. Current Reviews in Musculoskeletal Medicine 2011;4(1):11–15. Batailler C, Hannouche D, Benazzo F, Parratte S. Concepts and techniques of a new robotically assisted technique for total knee arthroplasty: the ROSA knee system. Archives of Orthopaedic and Trauma Surgery 2021;141(12):2049–58. Fu Y, Wang M, Liu Y, Fu Q. Alignment outcomes in navigated total knee arthroplasty: a meta-analysis. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA 2012;20(6):1075–82. Gustke KA, Simon P. Two-Year Outcome Comparison of a Matched Set of Total Knee Arthroplasties Performed With Robotic-Arm-Assisted Functional Alignment Balancing or Manual Instrument-Assisted Adjusted Mechanical Alignment. The Journal of Arthroplasty February 2025:S0883-5403(25)00179-2. Croppi C, Delaigue F, Guinebertière V, Devriese F, Bizot P, Descamps J, et al. Catastrophism and anxiety are risk factors of chronic pain after total knee arthroplasty: a prospective cohort study. Bone & Joint Open 2025;6(7):755–63. Parratte S, Van Overschelde P, Bandi M, Ozturk BY, Batailler C. An anatomo-functional implant positioning technique with robotic assistance for primary TKA allows the restoration of the native knee alignment and a natural functional ligament pattern, with a faster recovery at 6 months compared to an adjusted mechanical technique. Knee Surgery, Sports Traumatology, Arthroscopy 2023;31(4):1795. Chompoosang T, Ketkaewsuwan U, Ploynumpon P. Comparative effects of mechanical and functional alignment in bilateral robotic total knee arthroplasty: a randomized controlled trial. Arthroplasty (London, England) 2025;7(1):25. Lee JH, Kwon SC, Hwang JH, Lee JK, Kim JI. Functional alignment maximises advantages of robotic arm-assisted total knee arthroplasty with better patient-reported outcomes compared to mechanical alignment. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA 2024;32(4):896–906. Young SW, Tay ML, Kawaguchi K, van Rooyen R, Walker ML, Farrington WJ, et al. The John N. Insall Award: Functional Versus Mechanical Alignment in Total Knee Arthroplasty: A Randomized Controlled Trial. The Journal of Arthroplasty February 2025:S0883-5403(25)00193-7. Yang H, Park C, Cheon J, Hwang J, Seon J. Comparison of Outcomes Between Functionally and Mechanically Aligned Total Knee Arthroplasty: Analysis of Parallelism to the Ground and Weight-Bearing Position of the Knee Using Hip-to-Calcaneus Radiographs. Journal of Personalized Medicine 2025;15(3):91. Fontalis A, Kayani B, Asokan A, Haddad IC, Tahmassebi J, Konan S, et al. Inflammatory Response in Robotic-Arm-Assisted Versus Conventional Jig-Based TKA and the Correlation with Early Functional Outcomes: Results of a Prospective Randomized Controlled Trial. JBJS 2022;104(21):1905. Maman D, Laver L, Becker R, Mahamid A, Berkovich Y. Robotic-assisted total knee arthroplasty reduces postoperative complications and length of stay without increased cost compared to navigation-guided techniques: A national analysis. https://onlinelibrary.wiley.com/doi/abs/10.1002/ksa.12348 . Accessed 11.12.2024. Kayani B, Konan S, Huq SS, Tahmassebi J, Haddad FS. Robotic-arm assisted total knee arthroplasty has a learning curve of seven cases for integration into the surgical workflow but no learning curve effect for accuracy of implant positioning. Knee Surgery, Sports Traumatology, Arthroscopy 2019;27(4):1132-41. Spece H, Kurtz MA, Piuzzi NS, Kurtz SM. Patient-reported outcome measures offer little additional value two years after arthroplasty: a systematic review and meta-analysis. The Bone & Joint Journal 2025;107-B(3):296–307. Bouché P-A, Corsia S, Dechartres A, Resche-Rigon M, Nizard R. Are There Differences in Accuracy or Outcomes Scores Among Navigated, Robotic, Patient-specific Instruments or Standard Cutting Guides in TKA? A Network Meta-analysis. Clinical orthopaedics and related research 2020;478(9):2105–16. Melinte MA, Simionescu L, Tăbăcar M, Blănaru V, Melinte RM. Comparison between robotic-assisted and navigation-assisted total knee arthroplasty shows comparable outcomes: A systematic review and meta-analysis. Journal of Orthopaedics 2025;68:96–104. Pius AK, Sporer SM, Sterling O, De M, Jahan M, Browne JA, et al. Navigated and Robotic Total Knee Arthroplasty Do Not Confer Improved 5-Year Survivorship Compared to Conventional Total Knee Arthroplasty: An Analysis From the American Joint Replacement Registry. The Journal of Arthroplasty March 2025:S0883-5403(25)00259-1. Table 2 and 3 Table 2 and 3 are available in the Supplementary Files section. Additional Declarations No competing interests reported. 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Bouche","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFElEQVRIiWNgGAWjYDACZijNJwEkGBuAhAQD42OwkAQBLWxIWpiN8WqBAWQtbNL4tJizMx/7XFHBIM8m3fzsAeMOm8T+2c3Hqgvbahn4Zzdg1WLZzJY888wZBsM2mWPmBoxn0hJn3DmWdntm23EGiTsHsGoxOMxjzNjY9p+xTSLBTIKx7XDiBokcs9u8bccYDCQScGjh/8zY+I/Bvk0i/RtUS/63YvxaeJgZGxsYEtuAhsNsYWPmbavBqQXoF2PGhmMMyW0yZ8okEs+kGc+4kWYszXPuAI/EDexazPkPP2ZsqGGw7Zdu3ybxcYeNbP+M5Iefecrq5Phn4HAYCg9JzWEerOoxtCCBOlwSo2AUjIJRMPIAAMAcVyMXEdKSAAAAAElFTkSuQmCC","orcid":"","institution":"University Hospital of Geneva","correspondingAuthor":true,"prefix":"","firstName":"Pierre-Alban","middleName":"","lastName":"Bouche","suffix":""},{"id":615231066,"identity":"d836b5fd-af04-4f4e-a496-786cc113f486","order_by":1,"name":"Halah Kutaish","email":"","orcid":"","institution":"University Hospital of Geneva","correspondingAuthor":false,"prefix":"","firstName":"Halah","middleName":"","lastName":"Kutaish","suffix":""},{"id":615231067,"identity":"500d9e99-7d2a-4f46-9cbb-6476211c5314","order_by":2,"name":"Toscan Donat","email":"","orcid":"","institution":"University Hospital of Geneva","correspondingAuthor":false,"prefix":"","firstName":"Toscan","middleName":"","lastName":"Donat","suffix":""},{"id":615231068,"identity":"e45cdfa8-9b6c-43ba-ae84-05b0350cb156","order_by":3,"name":"William Digiovanni","email":"","orcid":"","institution":"Massachusetts General Hospital","correspondingAuthor":false,"prefix":"","firstName":"William","middleName":"","lastName":"Digiovanni","suffix":""},{"id":615231069,"identity":"3ad7ae76-dd05-4352-835b-080d8bb498cc","order_by":4,"name":"Anne Lubbeke","email":"","orcid":"","institution":"University Hospital of Geneva","correspondingAuthor":false,"prefix":"","firstName":"Anne","middleName":"","lastName":"Lubbeke","suffix":""},{"id":615231070,"identity":"cf821355-6228-4121-abf4-e8ce1ef1f0dd","order_by":5,"name":"Matthieu Zingg","email":"","orcid":"","institution":"University Hospital of Geneva","correspondingAuthor":false,"prefix":"","firstName":"Matthieu","middleName":"","lastName":"Zingg","suffix":""},{"id":615231071,"identity":"f5a8275c-d695-4501-97d9-2aa008f83ec5","order_by":6,"name":"Didier Hannouche","email":"","orcid":"","institution":"University Hospital of Geneva","correspondingAuthor":false,"prefix":"","firstName":"Didier","middleName":"","lastName":"Hannouche","suffix":""}],"badges":[],"createdAt":"2026-03-25 19:38:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9226681/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9226681/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106070607,"identity":"7703d100-ee08-49b8-aba4-4a409c6f8be1","added_by":"auto","created_at":"2026-04-03 06:28:50","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":12370,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-9226681/v1/8f948dc53cf7402db19375ee.png"},{"id":106094949,"identity":"1df1002f-511b-4ac5-a021-164d2e589f3b","added_by":"auto","created_at":"2026-04-03 11:43:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":11165,"visible":true,"origin":"","legend":"\u003cp\u003eSix-month VAS pain score distribution (A) and proportion of patients reporting chronic pain (B) across groups without any significant differences.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-9226681/v1/3cca921a4050741f45455dbd.png"},{"id":106070609,"identity":"3e6b9328-cc3e-4a3d-904c-d3b8929dda45","added_by":"auto","created_at":"2026-04-03 06:28:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":206536,"visible":true,"origin":"","legend":"\u003cp\u003eProportion of patients reporting no symptoms ('None') by WOMAC item and group.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-9226681/v1/f34a670b61a16cf627f9328b.png"},{"id":107382381,"identity":"5feb3604-469f-4b87-84fb-c3380187ffb7","added_by":"auto","created_at":"2026-04-21 02:55:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":550357,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9226681/v1/7f3106a4-8dee-4588-899c-1156b779d079.pdf"},{"id":106070604,"identity":"ecc9c927-16fd-4af2-91b1-1acaf53cdf27","added_by":"auto","created_at":"2026-04-03 06:28:50","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":16006,"visible":true,"origin":"","legend":"","description":"","filename":"Table2.docx","url":"https://assets-eu.researchsquare.com/files/rs-9226681/v1/4d3a974d58ae6bcabe72e2fb.docx"},{"id":106094470,"identity":"3896c970-489a-4b12-945d-8a7b393fab07","added_by":"auto","created_at":"2026-04-03 11:42:40","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":21945,"visible":true,"origin":"","legend":"","description":"","filename":"Table3.docx","url":"https://assets-eu.researchsquare.com/files/rs-9226681/v1/3a73d5eda850e0a3585f57cf.docx"},{"id":106094742,"identity":"887a8b98-13a2-4945-ba7e-09796095d083","added_by":"auto","created_at":"2026-04-03 11:43:11","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":23760,"visible":true,"origin":"","legend":"","description":"","filename":"Strobe.docx","url":"https://assets-eu.researchsquare.com/files/rs-9226681/v1/dcf5c1047e2418b21748852d.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparison of Functional and Mechanical Alignment in Posterior-Stabilized Total Knee Arthroplasty: A Propensity-Matched Retrospective Cohort Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eTotal knee arthroplasty (TKA) is one of the most frequently performed surgical procedures worldwide \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Moreover TKA demand is projected to increase substantially in the coming years due to aging populations and the rising prevalence of degenerative joint disease \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Despite the overall success of TKA, an estimated 10% to 20% of patients remain dissatisfied after the operation \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. This dissatisfaction underscores the importance of optimizing long-term outcomes and tailoring surgical techniques to patient-specific anatomy and function.\u003c/p\u003e \u003cp\u003eMalalignment of prosthetic components can adversely affect functional outcomes and implant longevity, leading to accelerated polyethylene wear and early implant loosening \u003csup\u003e\u003cspan additionalcitationids=\"CR7 CR8 CR9\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Historically, alignment strategies have relied on the principle of mechanical alignment (MA), which aims to restore a neutral coronal alignment between the hip, knee, and ankle. A mechanical axis within \u0026plusmn;\u0026thinsp;3\u0026deg; of neutral varus or valgus has traditionally been associated with improved implant survival \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. However, the reconstructed neutral mechanical axis, perpendicular to the joint line, often diverges from the native anatomical and kinematic characteristics of the knee. This mismatch has been identified as a potential contributor to patient dissatisfaction \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, particularly when it results in unintended alterations to joint line obliquity or imbalances in medial-lateral soft tissue tension\u0026mdash;factors not addressed by the mechanical alignment philosophy.\u003c/p\u003e \u003cp\u003eAs such, alternative alignment strategies have since emerged. Kinematic alignment (KA), initially proposed by Howell et al. \u003csup\u003e13,14\u003c/sup\u003e, seeks to restore the patient\u0026rsquo;s pre-arthritic joint line and limb orientation by matching the thickness of the resected bone and cartilage with that of the prosthetic components, thereby preserving the native orientation and kinematics of the knee. Despite deviating from the neutral mechanical axis, KA has not been associated with increased implant failure in mid-term studies, and the relationship between mechanical axis alignment within \u0026plusmn;\u0026thinsp;3\u0026deg; and implant survivorship remains unconfirmed \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. However, no conclusive evidence to date has demonstrated the superiority of KA over MA in terms of functional outcomes \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eMore recently, the adoption of robotic-assisted TKA has enabled the implementation of functional alignment (FA)\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Functional alignment aims to achieve a balanced knee in both extension and flexion by reproducing the patient\u0026rsquo;s native anatomy and soft tissue envelope. Robotic systems allow for real-time intraoperative assessment of knee alignment, bone resection, ligament balance, and joint space symmetry, facilitating individualized implant positioning that aims to restore native knee kinematics while compensating for arthritic changes \u003csup\u003e\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Although functional alignment is increasingly adopted in clinical practice, comparative data with traditional mechanical alignment remains limited, especially for postero-stabilized (PS) TKA \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe present study means to compare mechanical and functional alignment in TKA in terms of patient-reported and functional outcomes at a minimum of one year follow-up. By evaluating these two alignment philosophies in a modern, technologically enhanced surgical setting, we aim to provide further evidence to guide surgical decision-making and improve patient satisfaction following TKA.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e The Cantonal Commission for Research Ethics of Geneva (N\u0026deg;: 2024\u0026thinsp;\u0026minus;\u0026thinsp;01604) approved this single-center, retrospective study of prospectively collected data in accordance with the Declaration of Helsinki. All patients were informed about the study. All patients have given their consent.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatients\u003c/h2\u003e \u003cp\u003eThis retrospective cohort study included all patients who underwent primary TKA for osteoarthritis between January 2016 and April 2024 and received a cemented posterior-stabilized Persona total knee arthroplasty (Zimmer Biomet) by the same senior orthopedic surgeon. Between 2016 and 2019, 118 patients received MA TKA using a navigation system (OrthoKey, Zimmer). From 2019 to April 2024, 199 patients underwent FA TKA with robotic assistance (ROSA system, Zimmer). After propensity score matching, 172 patients remained for final analysis, with 86 in each group (Fig.\u0026nbsp;1).\u003c/p\u003e \u003cp\u003eThe overall cohort had a mean age of 72.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9 years (range: 56\u0026ndash;91), and 68.6% were women (118/172). Mean body mass index (BMI) was 28.6\u0026thinsp;\u0026plusmn;\u0026thinsp;5.7 kg/m\u0026sup2; (range: 18.3\u0026ndash;43.6). Preoperative alignment analysis showed a mean hip-knee-ankle (HKA) angle of 177.7\u0026deg; \u0026plusmn; 7.9\u0026deg; (range: 153\u0026ndash;195\u0026deg;), a mean lateral distal femoral angle (LDFA) of 88.0\u0026deg; \u0026plusmn; 3.0\u0026deg; (range: 78\u0026ndash;98\u0026deg;), and a mean medial tibial plateau angle (MTPA) of 87.3\u0026deg; \u0026plusmn; 4.0\u0026deg; (range: 74\u0026ndash;97\u0026deg;).\u003c/p\u003e \u003cp\u003eBased on coronal alignment, 60.5% (101/167) of knees were classified as varus and 39.5% (66/167) as valgus. According to the CPAK classification, the distribution was as follows: Type I, 15.5% (25/167); Type II, 23.0% (37/167); Type III, 24.8% (40/167); Type IV, 11.2% (18/167); Type V, 14.9% (24/167); Type VI, 7.5% (12/167); Type VII, 2.5% (4/167); Type VIII, 0.0% (0/167); and Type IX, 0.6% (1/167). Mean follow-up duration was 4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1 years, with a significant difference between the MA group (5.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 years) and the FA group (2.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9 years) (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Demographic and baseline characteristics for both groups are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\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\u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" 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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMechanical aligment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFunctional alignment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e72.6 (8.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e71.4 (7.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.47\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eman\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e31.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e31.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ewoman\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e68.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e68.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e28.5(5.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e28.6(5.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.94\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eASA score\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.4(0.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.3(0.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSide\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e41.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e41.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e58.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e58.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHKA preop(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e178.9 (8.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e176.5(7.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDeformity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVarus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e51.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e69.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u003cspan type=\"BoldUnderline\" class=\"BoldUnderline\" name=\"Emphasis\"\u003e0.03\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eValgus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e48.2%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e31.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLDFA preop(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e87.7(2.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e88.1(3.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMPTA preop(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e87.5(3.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e85.9(3.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u003cspan type=\"BoldUnderline\" class=\"BoldUnderline\" name=\"Emphasis\"\u003e0.03\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCPAK preop\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e19.2%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e12.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e25.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e23.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e26.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e10.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e13.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e8.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVIII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIX\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSurgical Data\u003c/h3\u003e\n\u003cp\u003eAll procedures were performed using a medial parapatellar approach without a tourniquet, with cemented PS implants and patellar resurfacing. The alignment strategy differed between groups. In the mechanical alignment group, the objective was to restore a neutral mechanical axis (\u0026plusmn;\u0026thinsp;3\u0026deg;), targeting an MPTA and LDFA of 90\u0026deg; (\u0026plusmn;\u0026thinsp;3\u0026deg;). The functional alignment group instead utilized individualized bone resections to recreate each patient\u0026rsquo;s native anatomy and knee kinematics by balancing the medial and lateral collateral ligaments in both flexion and extension. The detailed parameters and boundaries defining the functional alignment strategy are presented in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eIntraoperative collateral ligament tension was assessed using the ROSA software and quantified as medial and lateral joint line openings (in millimeters). In the functional alignment group, intraoperative data were available for 68 of the 86 patients. Based on the criteria defined in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, 91% of TKAs (62/68) were considered balanced in extension, with a mean medial\u0026ndash;lateral gap difference of \u0026minus;\u0026thinsp;0.28\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1 mm. In flexion, 100% (68/68) were balanced, with a mean medial-lateral difference of \u0026minus;\u0026thinsp;0.92\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 mm. As defined by the flexion-extension gap difference, 85.3% (58/68) were balanced medially, with a mean delta of \u0026minus;\u0026thinsp;0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 mm.\u003c/p\u003e\n\u003cp\u003eSurgical technique, perioperative management, and rehabilitation protocols remained consistent throughout the study period. All patients followed an identical postoperative rehabilitation program, which included early full weight-bearing and mobilization using two crutches beginning the day after surgery.\u003c/p\u003e\n\u003ch3\u003eVariables/ Outcomes\u003c/h3\u003e\n\u003cp\u003eDemographic data including age, sex, BMI, and American Society of Anesthesiologists (ASA) physical status classification were collected for each patient on the day of surgery. Clinical follow-up data were recorded during hospitalization and at one year postoperatively. Functional outcomes included the following validated scores: Visual Analogue Scale (VAS) for pain, Oxford Knee Score (OKS), SF-12 (physical and mental components), Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain and function subscales, the Simple Knee Value (SKV), the Forgotten Joint Score (FJS), and the Net Promoter Score (NPS). For the WOMAC and FJS, individual item analysis was also performed. Data on surgical complications were collected, as well as data on surgical revision and reoperation. Operative time and length of hospital stay were also recorded.\u003c/p\u003e \u003cp\u003eThe primary outcome was the proportion of patients experiencing moderate to severe pain (defined as VAS\u0026thinsp;\u0026ge;\u0026thinsp;4/10, referred to as chronic pain \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e) after 6 months postoperatively.\u003c/p\u003e \u003cp\u003eSecondary outcomes included comparisons between groups for pain and functional scores, length of hospital stay, operative time, and complication rates at 1-year follow-up.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eA total of 70 patients per group was estimated to be necessary to detect a 1.0-point difference in pain scores between groups, assuming a standard deviation of 2.0, with a two-sided alpha level of 0.05 and 80% statistical power. To ensure comparability between groups and reduce the influence of confounding factors and selection bias, a propensity score matching approach was applied. The propensity score incorporated age at surgery, sex, and BMI. Patients in the MA group were matched 1:1 to those in the FA group using a logit model with a caliper width of 0.05. Categorical variables are presented as counts and percentages, whereas continuous variables are expressed as means with standard deviations. Group comparisons were performed using Fisher\u0026rsquo;s exact test for categorical variables and the Wilcoxon rank-sum test for continuous variables. A p-value\u0026thinsp;\u0026le;\u0026thinsp;0.05 was considered statistically significant. All analyses were conducted using R software (version 3.5.0; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.r-project.org/\u003c/span\u003e\u003cspan address=\"https://www.r-project.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003ePain outcomes\u003c/h2\u003e \u003cp\u003eAt six months postoperatively, the mean VAS pain score was 1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.38 (range: 0\u0026ndash;10) in the MA group and 1.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2.20 (range: 0\u0026ndash;8) in the FA group, with no statistically significant difference between groups (p\u0026thinsp;=\u0026thinsp;0.69, Fig.\u0026nbsp;2). The proportion of patients reporting chronic pain was 17.4% (30/172), with no significant difference between the MA (15.1%, 13/86) and FA groups (19.8%, 17/86; p\u0026thinsp;=\u0026thinsp;0.55, Fig.\u0026nbsp;2).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eClinical outcomes\u003c/h3\u003e\n\u003cp\u003eBaseline preoperative scores were comparable between the two groups (Table\u0026nbsp;3). At one year postoperatively, no statistically significant differences were observed between the MA and FA groups across all clinical outcome measures, including SF-12 mental and physical scores, WOMAC pain and function subscales, OKS function and pain subscales, FJS, and SKV (all p\u0026thinsp;\u0026gt;\u0026thinsp;0.05, Table\u0026nbsp;3).\u003c/p\u003e \u003cp\u003eAlthough none of these differences reached statistical significance, the FA group consistently demonstrated numerically higher scores across several domains, including the SF-12 (mental and physical), WOMAC pain, OKS (total and subscales), and SKV. Changes from baseline to one year are also detailed in Table\u0026nbsp;3 and did not differ significantly between groups.\u003c/p\u003e \u003cp\u003eAnalysis of individual WOMAC items revealed two statistically significant differences favoring the FA group. For the items \u0026ldquo;Pain while walking on a flat surface\u0026rdquo; and \u0026ldquo;Difficulty walking on a flat surface,\u0026rdquo; a greater proportion of patients in the FA group reported no pain (64.7% vs 49.3%; p\u0026thinsp;=\u0026thinsp;0.02) and no difficulty (64.7% vs 52.9%; p\u0026thinsp;=\u0026thinsp;0.02), respectively (Fig.\u0026nbsp;3). No significant differences were found in individual FJS items.\u003c/p\u003e \u003cp\u003ePatient satisfaction, assessed by the NPS, was comparable between groups. The proportion of promoter patients (NPS\u0026thinsp;\u0026gt;\u0026thinsp;8/10) was similar (MA: 85.5% vs FA: 84.6%; p\u0026thinsp;\u0026gt;\u0026thinsp;0.90), as was the proportion of detractor patients (NPS\u0026thinsp;\u0026lt;\u0026thinsp;7/10; MA: 8.1% vs FA: 4.6%; p\u0026thinsp;=\u0026thinsp;0.49).\u003c/p\u003e \u003cp\u003e \u003cem\u003ePerioperative Outcomes and Complications\u003c/em\u003eMmean hospital stay was significantly shorter in the FA group compared to the MA group (7.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0 vs 9.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 days; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Similarly, the mean operative time was significantly lower in the FA group (101.7\u0026thinsp;\u0026plusmn;\u0026thinsp;16.7 vs 119.6\u0026thinsp;\u0026plusmn;\u0026thinsp;16.0 minutes; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). There were no significant differences between groups regarding early complications or revision rates. The overall complication rate was 7.0% (6/86) in the MA group\u0026mdash;comprising three cases of postoperative stiffness, one hematoma, one debridement for a hematogenous infection and one case of persistent pain\u0026mdash;compared to 4.7% (4/86) in the FA group, which included one traumatic open joint injury, one superficial infection at the pins sites, one hematoma, and one medial collateral ligament injury (p\u0026thinsp;=\u0026thinsp;0.75). The overall revision rate remained low in both groups: 1.2% (1/86) in the MA group (one aseptic loosening) and 0.0% (0/86) in the FA group (p\u0026thinsp;=\u0026thinsp;1.00).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study demonstrates that at one-year follow-up, no statistically significant differences were observed between MA and FA in terms of postoperative pain, global functional outcomes, or patient satisfaction following TKA with PS implants. However, patients in the FA group exhibited slightly higher, albeit non-significant, scores in several functional and quality-of-life domains, suggesting a potentially favorable trend toward this alignment strategy. These findings raise the question of the sensitivity of global scores in detecting clinically meaningful differences. To our knowledge, this is the first study to compare MA and FA with respect to PROs in a homogeneous cohort receiving the same posterior-stabilized implant.\u003c/p\u003e \u003cp\u003eOur observations align with recent literature. Several comparative studies between MA and FA have reported minimal or no differences in global pain and function scores \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan additionalcitationids=\"CR24 CR25\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, though a trend favoring FA is often observed without always reaching statistical significance. Lee et al. \u003csup\u003e25\u003c/sup\u003e compared 70 robot-assisted MA, 70 conventional MA, and 70 robot-assisted FA patients and reported significantly better functional outcomes at 6 and 12 months in the FA group. Similarly, Gustke et al. \u003csup\u003e21\u003c/sup\u003e compared 140 FA and 70 MA patients (PS and CS implants) and reported a higher FJS in the FA group (66.3\u0026thinsp;\u0026plusmn;\u0026thinsp;26.2 vs 60.4\u0026thinsp;\u0026plusmn;\u0026thinsp;29.2; p\u0026thinsp;=\u0026thinsp;0.155), as well as significantly greater maximal flexion (125.4\u0026deg; \u0026plusmn; 12.5\u0026deg; vs 120.9\u0026deg; \u0026plusmn; 7.2\u0026deg;; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eIn a randomized trial, Young et al. \u003csup\u003e26\u003c/sup\u003e compared 121 MA and 123 FA cases (CR TKA) and observed significant differences favoring FA in the KOOS symptoms subscale (86.6\u0026thinsp;\u0026plusmn;\u0026thinsp;12.9 vs 82.5\u0026thinsp;\u0026plusmn;\u0026thinsp;14.0; p\u0026thinsp;=\u0026thinsp;0.01) and quality of life subscale (76.4\u0026thinsp;\u0026plusmn;\u0026thinsp;21.7 vs 64.2\u0026thinsp;\u0026plusmn;\u0026thinsp;19.2; p\u0026thinsp;=\u0026thinsp;0.02). In our cohort, a detailed analysis of individual WOMAC items revealed statistically significant differences favoring FA in certain domains: a higher proportion of patients reported being pain-free (64.7% vs 49.3%; p\u0026thinsp;=\u0026thinsp;0.02) and experienced less difficulty walking on a flat surface (64.7% vs 52.9%; p\u0026thinsp;=\u0026thinsp;0.02). These results highlight the complexity of functional evaluation after TKA and underscore the limitations of global scores in capturing the nuances of patient-perceived recovery. Specifically, ceiling or floor effects may mask subtle but clinically meaningful benefits in specific subpopulations. A more focused approach targeting specific subdomains of function or quality of life may better capture the potential advantages of personalized alignment strategies.\u003c/p\u003e \u003cp\u003eFurthermore, other pathophysiological mechanisms may help explain the functional benefits observed with FA. In a randomized trial comparing 29 FA to 31 MA patients with CR implants, Manara et al. \u003csup\u003e17\u003c/sup\u003e found no significant differences in PROMs but reported a higher incidence of medial pivot kinematics in the FA group (58.6% vs 19.4% in MA). This kinematic pattern was associated with improved PROMs compared to symmetrical rollback or lateral pivot patterns, possibly because medial pivot enhances quadriceps mechanics and patellar tracking. This observation may help explain the superior performance of FA patients in our study regarding flat-surface walking in the WOMAC score. In this group, the mean medial-lateral gap difference was \u0026minus;\u0026thinsp;0.28\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1 mm in extension, \u0026minus;\u0026thinsp;0.92\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 mm in flexion, and the mean flexion-extension gap difference for the medial compartment was \u0026minus;\u0026thinsp;0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 mm. Preservation of key ligaments and restoration of the native joint line likely contribute to this stability and superior function following FA-TKA. Finally, Yang et al. \u003csup\u003e27\u003c/sup\u003e showed that FA improved joint line parallelism to the floor and resulted in more neutral weight-bearing alignment on gait analysis, compared to MA. These biomechanical parameters may also contribute to the better functional tolerance of FA in certain daily activities.\u003c/p\u003e \u003cp\u003eAnother notable finding was that hospital stay was shorter in the FA group compared to the MA group (7.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0 vs 9.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 days; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). This difference is likely related to the use of different technologies in the MA and the FA groups. Recent research indicates that the early inflammatory response after robotic surgery is reduced, resulting in decreased postoperative pain during the initial days and facilitating earlier discharge \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. Furthermore, robotic placement of cutting guides and accurate bone cuts save time once the learning curve has been surpassed \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe current study has several limitations. First, this research is a retrospecitve cohort study based on a prospective institutional arthroplasty registry,not a randomized controlled trial. However, comparable groups were obtained for age, sex, and BMI through propensity score matching. Second, the follow-up duration is relatively short at oneyear. Nevertheless, a recent study by Spece et al.\u003csup\u003e31\u003c/sup\u003e suggests that long-term PROMs beyond one or two years are often incomplete and lose sensitivity over time. Third, different technologies were used between groups: navigation in the MA group and robotic surgery in the FA group. However, no study to date has demonstrated a difference in functional outcomes between these two cutting guide technologies \u003csup\u003e\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eAt one-year follow-up, functional alignment demonstrated comparable outcomes to mechanical alignment in global PROs, pain, and patient satisfaction after posterior-stabilized total knee arthroplasty. However, the FA group exhibited favorable trends and significant improvements in selected functional items, suggesting potential clinical benefits that may not be fully captured by composite scores. These findings support growing interest in personalized alignment strategies and highlight the importance of using more sensitive, domain-specific measures when evaluating patient outcomes after TKA.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eASA \u0026nbsp; \u0026nbsp; \u0026nbsp; American Society of Anesthesiologists\u003c/p\u003e\n\u003cp\u003eBMI \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Body Mass Index\u003c/p\u003e\n\u003cp\u003eCR\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp; \u0026nbsp; Cruciate retaining\u003c/p\u003e\n\u003cp\u003eCS\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u0026nbsp; \u0026nbsp; Cruciate sacrificing\u003c/p\u003e\n\u003cp\u003eFA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Functional Alignment\u003c/p\u003e\n\u003cp\u003eFJS \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Forgotten Joint Score\u003c/p\u003e\n\u003cp\u003eHKA \u0026nbsp;\u0026nbsp;\u0026nbsp; Hip Knee Ankle angle\u003c/p\u003e\n\u003cp\u003eJLO \u0026nbsp; \u0026nbsp; \u0026nbsp;Joint Line Obliquity\u003c/p\u003e\n\u003cp\u003eLDFA \u0026nbsp; \u0026nbsp;Lateral Distal Femur angle\u003c/p\u003e\n\u003cp\u003eOKS \u0026nbsp; \u0026nbsp; \u0026nbsp;Oxford Knee Score\u003c/p\u003e\n\u003cp\u003eMA \u0026nbsp; \u0026nbsp; \u0026nbsp; Mechanical alignment\u003c/p\u003e\n\u003cp\u003eMPTA \u0026nbsp; Medial Proximal Tibial Angle\u003c/p\u003e\n\u003cp\u003eNPS \u0026nbsp; \u0026nbsp; Net Promoter Score\u003c/p\u003e\n\u003cp\u003ePS \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Postero stabilized\u003c/p\u003e\n\u003cp\u003eSKV \u0026nbsp; \u0026nbsp; \u0026nbsp;Simple Knee Value\u003c/p\u003e\n\u003cp\u003eTKA \u0026nbsp; \u0026nbsp; Total Knee Arthroplasty\u003c/p\u003e\n\u003cp\u003eVAS \u0026nbsp; \u0026nbsp; Visual Analogue Scale\u003c/p\u003e\n\u003cp\u003eWOMAC \u0026nbsp;Western Ontario and McMaster Universities Arthritis Index\u003c/p\u003e"},{"header":"Declarations","content":"\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eThe researchers did not receive any funding to conduct this study.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eEthical approval:\u003c/strong\u003e This study was approved by the local ethics committee under the N\u0026deg;: 2024-01604.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eInformed consent:\u0026nbsp;\u003c/strong\u003eAll patients were informed about the study. All patients have given their consent.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eDeclaration of AI Usage:\u0026nbsp;\u003c/strong\u003enone\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eConsent for publication:\u0026nbsp;\u003c/strong\u003eConsent for publication: All authors have read and approved the manuscript and consent to its publication.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBlom AW, Donovan RL, Beswick AD, Whitehouse MR, Kunutsor SK. Common elective orthopaedic procedures and their clinical effectiveness: umbrella review of level 1 evidence. BMJ 2021;374:n1511.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBouch\u0026eacute; P-A, Kutaish H, Gasparutto X, Lubbeke A, Miozzari HH, Hannouche D. Coronal Plane Alignment of the Knee Classification in Osteoarthritic Knees: Poor to Moderate Reliability and Implications for Imaging Choice. The Journal of Arthroplasty 2026;41(3):725\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarr AJ, Robertsson O, Graves S, Price AJ, Arden NK, Judge A, et al. Knee replacement. Lancet (London, England) 2012;379(9823):1331\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. The Journal of Bone and Joint Surgery American Volume 2007;89(4):780\u0026ndash;85.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeFrance MJ, Scuderi GR. Are 20% of Patients Actually Dissatisfied Following Total Knee Arthroplasty? A Systematic Review of the Literature. The Journal of Arthroplasty 2023;38(3):594\u0026ndash;99.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchroer WC, Berend KR, Lombardi AV, Barnes CL, Bolognesi MP, Berend ME, et al. Why are total knees failing today? Etiology of total knee revision in 2010 and 2011. The Journal of Arthroplasty 2013;28(8 Suppl):116\u0026ndash;19.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMason JB, Fehring TK, Estok R, Banel D, Fahrbach K. Meta-analysis of alignment outcomes in computer-assisted total knee arthroplasty surgery. The Journal of Arthroplasty 2007;22(8):1097\u0026ndash;1106.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. The Journal of Bone and Joint Surgery British Volume 1991;73(5):709\u0026ndash;14.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBargren JH, Blaha JD, Freeman MA. Alignment in total knee arthroplasty. Correlated biomechanical and clinical observations. Clinical Orthopaedics and Related Research 1983;(173):178\u0026ndash;83.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLongstaff LM, Sloan K, Stamp N, Scaddan M, Beaver R. Good alignment after total knee arthroplasty leads to faster rehabilitation and better function. The Journal of Arthroplasty 2009;24(4):570\u0026ndash;78.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRivi\u0026egrave;re C, Iranpour F, Auvinet E, Howell S, Vendittoli P-A, Cobb J, et al. Alignment options for total knee arthroplasty: A systematic review. Orthopaedics \u0026amp; traumatology, surgery \u0026amp; research: OTSR 2017;103(7):1047\u0026ndash;56.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOussedik S, Abdel MP, Victor J, Pagnano MW, Haddad FS. Alignment in total knee arthroplasty. The Bone \u0026amp; Joint Journal 2020;102-B(3):276\u0026ndash;79.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHowell SM, Howell SJ, Kuznik KT, Cohen J, Hull ML. Does a kinematically aligned total knee arthroplasty restore function without failure regardless of alignment category? Clinical Orthopaedics and Related Research 2013;471(3):1000\u0026ndash;1007.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee YS, Howell SM, Won Y-Y, Lee O-S, Lee SH, Vahedi H, et al. Kinematic alignment is a possible alternative to mechanical alignment in total knee arthroplasty. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA 2017;25(11):3467\u0026ndash;79.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eParratte S, Pagnano MW, Trousdale RT, Berry DJ. Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern, cemented total knee replacements. The Journal of Bone and Joint Surgery American Volume 2010;92(12):2143\u0026ndash;49.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGibbons JP, Zeng N, Bayan A, Walker ML, Farrington B, Young SW. No Difference in 10-year Clinical or Radiographic Outcomes Between Kinematic and Mechanical Alignment in TKA: A Randomized Trial. Clinical Orthopaedics and Related Research 2025;483(1):140\u0026ndash;49.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eManara JR, Steer R, Whitehouse SL, Collopy D, Clark GW. Functional alignment restores native kinematics more consistently than mechanical axis alignment in total knee arthroplasty. The Bone \u0026amp; Joint Journal 2025;107-B(4):423\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDesai AS, Dramis A, Kendoff D, Board TN. Critical review of the current practice for computer-assisted navigation in total knee replacement surgery: cost-effectiveness and clinical outcome. Current Reviews in Musculoskeletal Medicine 2011;4(1):11\u0026ndash;15.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBatailler C, Hannouche D, Benazzo F, Parratte S. Concepts and techniques of a new robotically assisted technique for total knee arthroplasty: the ROSA knee system. Archives of Orthopaedic and Trauma Surgery 2021;141(12):2049\u0026ndash;58.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFu Y, Wang M, Liu Y, Fu Q. Alignment outcomes in navigated total knee arthroplasty: a meta-analysis. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA 2012;20(6):1075\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGustke KA, Simon P. Two-Year Outcome Comparison of a Matched Set of Total Knee Arthroplasties Performed With Robotic-Arm-Assisted Functional Alignment Balancing or Manual Instrument-Assisted Adjusted Mechanical Alignment. The Journal of Arthroplasty February 2025:S0883-5403(25)00179-2.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCroppi C, Delaigue F, Guineberti\u0026egrave;re V, Devriese F, Bizot P, Descamps J, et al. Catastrophism and anxiety are risk factors of chronic pain after total knee arthroplasty: a prospective cohort study. Bone \u0026amp; Joint Open 2025;6(7):755\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eParratte S, Van Overschelde P, Bandi M, Ozturk BY, Batailler C. An anatomo-functional implant positioning technique with robotic assistance for primary TKA allows the restoration of the native knee alignment and a natural functional ligament pattern, with a faster recovery at 6 months compared to an adjusted mechanical technique. Knee Surgery, Sports Traumatology, Arthroscopy 2023;31(4):1795.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChompoosang T, Ketkaewsuwan U, Ploynumpon P. Comparative effects of mechanical and functional alignment in bilateral robotic total knee arthroplasty: a randomized controlled trial. Arthroplasty (London, England) 2025;7(1):25.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee JH, Kwon SC, Hwang JH, Lee JK, Kim JI. Functional alignment maximises advantages of robotic arm-assisted total knee arthroplasty with better patient-reported outcomes compared to mechanical alignment. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA 2024;32(4):896\u0026ndash;906.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYoung SW, Tay ML, Kawaguchi K, van Rooyen R, Walker ML, Farrington WJ, et al. The John N. Insall Award: Functional Versus Mechanical Alignment in Total Knee Arthroplasty: A Randomized Controlled Trial. The Journal of Arthroplasty February 2025:S0883-5403(25)00193-7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang H, Park C, Cheon J, Hwang J, Seon J. Comparison of Outcomes Between Functionally and Mechanically Aligned Total Knee Arthroplasty: Analysis of Parallelism to the Ground and Weight-Bearing Position of the Knee Using Hip-to-Calcaneus Radiographs. Journal of Personalized Medicine 2025;15(3):91.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFontalis A, Kayani B, Asokan A, Haddad IC, Tahmassebi J, Konan S, et al. Inflammatory Response in Robotic-Arm-Assisted Versus Conventional Jig-Based TKA and the Correlation with Early Functional Outcomes: Results of a Prospective Randomized Controlled Trial. JBJS 2022;104(21):1905.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMaman D, Laver L, Becker R, Mahamid A, Berkovich Y. Robotic-assisted total knee arthroplasty reduces postoperative complications and length of stay without increased cost compared to navigation-guided techniques: A national analysis. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://onlinelibrary.wiley.com/doi/abs/10.1002/ksa.12348\u003c/span\u003e\u003cspan address=\"https://onlinelibrary.wiley.com/doi/abs/10.1002/ksa.12348\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. Accessed 11.12.2024.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKayani B, Konan S, Huq SS, Tahmassebi J, Haddad FS. Robotic-arm assisted total knee arthroplasty has a learning curve of seven cases for integration into the surgical workflow but no learning curve effect for accuracy of implant positioning. Knee Surgery, Sports Traumatology, Arthroscopy 2019;27(4):1132-41.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSpece H, Kurtz MA, Piuzzi NS, Kurtz SM. Patient-reported outcome measures offer little additional value two years after arthroplasty: a systematic review and meta-analysis. The Bone \u0026amp; Joint Journal 2025;107-B(3):296\u0026ndash;307.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBouch\u0026eacute; P-A, Corsia S, Dechartres A, Resche-Rigon M, Nizard R. Are There Differences in Accuracy or Outcomes Scores Among Navigated, Robotic, Patient-specific Instruments or Standard Cutting Guides in TKA? A Network Meta-analysis. Clinical orthopaedics and related research 2020;478(9):2105\u0026ndash;16.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMelinte MA, Simionescu L, Tăbăcar M, Blănaru V, Melinte RM. Comparison between robotic-assisted and navigation-assisted total knee arthroplasty shows comparable outcomes: A systematic review and meta-analysis. Journal of Orthopaedics 2025;68:96\u0026ndash;104.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePius AK, Sporer SM, Sterling O, De M, Jahan M, Browne JA, et al. Navigated and Robotic Total Knee Arthroplasty Do Not Confer Improved 5-Year Survivorship Compared to Conventional Total Knee Arthroplasty: An Analysis From the American Joint Replacement Registry. The Journal of Arthroplasty March 2025:S0883-5403(25)00259-1.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Table 2 and 3","content":"\u003cp\u003eTable 2 and 3 are available in the Supplementary Files section.\u003c/p\u003e\n"}],"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":"Functional alignment, Robotic TKA, PROMs, TKA","lastPublishedDoi":"10.21203/rs.3.rs-9226681/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9226681/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground:\u003c/h2\u003e \u003cp\u003eWhile mechanical alignment (MA) has long been the gold standard in total knee arthroplasty (TKA), functional alignment (FA) has recently emerged as a promising alternative, particularly with the advent of robotic-assisted techniques. The present study aims to compare MA and FA in terms of pain, functional outcomes, and perioperative outcomes.\u003c/p\u003e\u003ch2\u003eMethods:\u003c/h2\u003e \u003cp\u003eThis single-center, retrospective cohort study included 172 patients undergoing primary TKA performed by the same surgeon between 2016 and 2024. Following a 1:1 propensity score matching, patients receiving MA-TKA with navigation (n\u0026thinsp;=\u0026thinsp;86) were compared with those receiving FA-TKA with robotic assistance (n\u0026thinsp;=\u0026thinsp;86). The primary outcome was the rate of chronic pain (VAS\u0026thinsp;\u0026ge;\u0026thinsp;4/10) at six months. Secondary outcomes included validated patient-reported outcomes (PROs: OKS, SF-12, WOMAC, FJS, SKV), Net Promoter Score (NPS), operative time, hospital stay, and complications.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eAt six months, the prevalence of chronic pain was comparable between groups (MA: 15.1%, FA: 19.8%; p\u0026thinsp;=\u0026thinsp;0.55). At one-year, PROs were similar across all metrics (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), although the FA group consistently demonstrated numerically superior scores. Two individual WOMAC items favored the FA group (pain and difficulty walking on flat surfaces; both p\u0026thinsp;=\u0026thinsp;0.02). Operative time (101.7\u0026thinsp;\u0026plusmn;\u0026thinsp;16.7 vs 119.6\u0026thinsp;\u0026plusmn;\u0026thinsp;16.0 min; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and hospital stay (7.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0 vs 9.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 days; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) were significantly shorter in the FA group. Complication and revision rates were low and not significantly different between groups.\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e \u003cp\u003eFunctional alignment in robotic-assisted TKA results in comparable pain and functional outcomes to mechanical alignment, while also demonstrating shorter operative time and hospital stay. These findings support the safety and clinical application of individualized alignment strategies in contemporary TKA.\u003c/p\u003e\u003ch2\u003eLevel of evidence\u003c/h2\u003e \u003cp\u003eIV, retrospective cohort\u003c/p\u003e","manuscriptTitle":"Comparison of Functional and Mechanical Alignment in Posterior-Stabilized Total Knee Arthroplasty: A Propensity-Matched Retrospective Cohort Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-03 06:28:38","doi":"10.21203/rs.3.rs-9226681/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":"b4aa9533-80f7-49cd-ae76-49aa133b7c0b","owner":[],"postedDate":"April 3rd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-21T02:55:31+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-03 06:28:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9226681","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9226681","identity":"rs-9226681","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}