Case Report Tarsocrural Synovitis and Superficial Digital Flexor Tendon Subluxation in a Polo Horse

Case Report Tarsocrural Synovitis and Superficial Digital Flexor Tendon Subluxation in a Polo Horse | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 12 December 2025 V1 Latest version Share on Case Report Tarsocrural Synovitis and Superficial Digital Flexor Tendon Subluxation in a Polo Horse Authors : Shehla Bokhari 0000-0003-0360-8380 [email protected] , Arslan Nazim , Muhammad Irfan , Arona Batool , and Mazhar Iqbal Authors Info & Affiliations https://doi.org/10.22541/au.176556797.77444139/v1 249 views 112 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Subluxation of the superficial digital flexor tendon (SDFT) is rare but occurs as a result of tearing or rupture of either the medial or lateral retinaculum, or both. This report describes sonographic findings and the treatment regimen opted for a case of chronic tarsocrural synovitis accompanied by a stable lateral subluxation of the SDFT with fibrosis, and fibrocartilaginous cap (FCC) remaining fixed in its position, in the left hind-limb of a Polo horse. Weekly laser therapy was instituted, initially augmenting a considerable reduction of the swelling and improvement in lameness grades; however, mild effusion persisted. Injection of methylprednisolone acetate (Depo-Medrol ®) 20 mg and cephradine (Velosef ®) 200 mg was injected at the effusion site, and injection of Tiludronate was recommended for the subsequent synovitis. The prognosis for the athletic career was grave for this mare; hence, pleasure riding and breeding were suggested. 1. Introduction In horses, Lameness is an abnormal gait or stance caused by structural or functional ailments of the locomotor system.[1,2,3] In the tarsocrural joint capsule, acute and chronic distention occur due to poor joint conformation, trauma, infection, degenerative joint disease (DJD), osteochondrosis, or idiopathy.[4] The luxation/subluxation of the tendinous structures associated with the hock also causes lameness. The top differentials include bog spavin, bone spavin, curb, fracture, thoroughpin, tendon, and muscle rupture. Ultrasonography detects abnormalities in 100% of lame horses’ tarsal joints, with synovitis (69.3%), collateral ligament injury (30.7%), and superficial digital flexor tendon injury (20%) being the most prevalent findings.[5] Superficial digital flexor tendon (SDFT) luxation is more common in young horses. The SDFT can be luxated/ subluxated by damage to its attachment at the point of the hock. Tendinitis or dislocation of the Superficial digital flexor (SDF), tendinitis of the gastrocnemius, or plantar ligament desmitis can also be observed in horses competing in high-speed events or jumping disciplines.[3] Luxation and subluxation of the SDFT mostly occur at the point of hock, commonly at the lateral aspect but rarely at the medial side. A combination of palpation, radiographs, and ultrasound examination is diagnostic in most cases.[3,6] Luxation of the SDF is usually treated conservatively. Surgical replacement and repair of the fibrous attachments is described, but is not always successful and is associated with complications. If the SDFT stabilizes in its new position, the horse tends to be sound.[3,7] Luxations of the SDFT have a good prognosis once the tendon is stable in the new position.[3,7] This case report describes the clinical findings, diagnosis, treatment, and outcome of a unique case of simultaneously occurring tarsocrural synovitis and stable subluxation of the SDFT in a mare that sustained chronic lameness for a year. 2. Materials and methods 2.1 Case description and Clinical Examination Findings For this clinical case, informed consent was taken from the owner regarding clinical examination, diagnostic procedures, and treatments, thereof. On August 12, 2024, an 11-year-old polo mare, Koka, at Jinnah Polo Fields, Lahore, presented with a history of chronic lameness from the left hind limb, during a polo game, a year ago. On physical examination, the mare manifested grade 2 lameness with an evident swelling at the plantar, lateral, and medial aspects of the left hock (Fig. 1). All the vitals were in the normal range. The Peroneus tertius muscle flexion test came out negative. Upon conformational examination, the mare was found to be slightly calf-kneed from the forelimb, camped under, and cow-hocked from the hind limb. On dynamic examination of the lameness, no abnormal head or neck movements were detected. Hip hike or hip roll on the opposite leg was evident with drifting away from the lame limb. On the spavin test, the gluteal rise on the left hind and hip hike on the right hind (shifting of weight) was observed. Fig. 1 Left hind limb swelling (A) Medial aspect; (B) Lateral aspect; (C) Plantar aspect 2.2 Diagnostic Procedures and Findings: A radiograph of the affected limb and normal limb was performed in normal and flexed presentations (Fig. 2). Radiographic findings show marked swelling and inflammation at the point of hock and level of long plantar ligament (Fig. 2) Ultrasound of the affected hock joint was conducted [8,9] with a linear probe at 9.5 MHz frequency. Sonography of affected hock shows Long Lateral Collateral Ligament (LLCL) strain lesions, aseptic synovitis (S) of the lateral side of the proximal intertarsal joint at the level of the Tibiotarsal and Fibular-Tarsal bone articulation lateral to the retinaculum of the SDFT Fig. 3 & Fig. 4. Irregular contour attributed to subchondral bony changes of Tibiotarsal bone (TT bone) Fig. 4. At the plantar aspect, strain lesions can be seen in the Superficial Digital Flexor Tendon (SDFT) at the insertion of the Gastrocnemius muscle Fig. 5. , Long Plantar Ligament (LPL) has strain lesions at the level of origin. SDFT was found at the plantarolateral aspect at the level of the tuber calcis instead of being in the midline position Fig. 5. SDFT medial & lateral retinaculum has tears evident as fiber disruption; and fibrosis of lateral attachment is seen as irregular fibers with hyperechogenicity, in Fig. 5. Tarsal sheath between SDFT and Deep Digital Flexor Tendon (DDFT) has fibrosis as the hyperechoic at level of 1B Fig. 5. Fig. 2 (A) Left hock Lateromedial (LM) view soft tissue swelling at the level of Long plantar ligament; (B) Left hock LM view flexed; (C) D60L/PlMO view soft tissue swelling at the level of Long plantar ligament (after laser therapy sessions); (D) Left hock dorsoplantar (DPl) view. (E) Right hock LM view flexed; (F) Right hock D60L/PlMO view Fig. 3. LLCL strain lesions at left hock Fig. 4 Left hock (A) Aseptic synovitis of proximal intertarsal joint (S); (B) Aseptic bursitis; (C) Subchondral bony changes in TT bone. Fig. 5 Left hock (A) strain lesion in SDFT at the insertion of gastrocnemius muscle (GST INS), TC, Tuber calcanei; (B) medial (MED RET TEAR) of SDFT; (C) lateral retinaculum (LAT RET TEAR) of SDFT, showing disrupted fiber pattern respectively; (D) Irregular fibers with hyper echogenicity; (E) SDFT displaced laterally and Lesion in LPL origin, TC, Tuber calcanei; (F) Fibrosis of the tarsal sheath between SDFT and DDFT at level of 1B. 3. Results 3.1 Treatment The mare received 10 sessions of continuous Low Level Laser Therapy (LLLT), having specifications of (Grady Medical Systems) ®, i.e., 810 nm, 4 × 750 mW over the hock, along with intravenous Flunixin Meglumine (Loxin-1.1 mg/kg) and compression bandaging. Laser sessions were administered thrice in the first week, twice in the second, and once weekly thereafter till the last session. By the 10th session, inflammation had subsided, revealing lateral luxation of the SDFT, though bursal swelling persisted. Fig. 6. After the 10th laser session, injections of methylprednisolone acetate (20 mg) and cephradine (200 mg) were administered. Inflammation subsequently resolved, and the mare appeared sound with no signs of lameness. Fig. 6 (A) Thorough pin (lateral inflammation of bursa at hock); (B) Fluid aspirated from the bursa. 4. Discussion Subluxation or luxation of the SDFT is a rare condition that typically occurs in horses at speed or due to trauma. [2] SDFT is a thin tendinous muscle arising from the caudal aspect of the distal femur, extending distally deep to the heads of the gastrocnemius muscle, with its tendon wraps medially around the gastrocnemius tendon and attaches superficially to the calcaneal tuberosity. [2] SDFT attachments over the calcaneal tuberosity with two bands of lateral retinaculum and one band of the medial retinaculum stabilize it over the caudal midline on the plantar aspect of the limb below the tarsus. The rupture in the attachment due to trauma, over-extension, and calcaneus tuberosity fracture leads to the tendon’s subluxation or luxation. [10] Three distinct forms of luxation of the SDFT have been reported: a) A lateral displacement with rupture of the medial calcaneal retinaculum. b) A medial displacement with the rupture of the lateral calcaneal retinaculum. c) A splitting of the fibrocartilagenous cap (FCC) of SDFT. [11,12,13] The dislocations/luxations can be unstable, partially stable, or complete and stable, with unstable partial dislocations causing more discomfort. [15] In stable luxation, the SDFT is displaced towards the lateral or medial, and its FCC is permanently positioned on the abaxial aspect of the calcaneal tuberosity, while in unstable SDFT, the FCC can move back and forth from the point of calcaneal tuberosity to its abaxial aspect during motion. [7,15] Because of swelling, diagnosing acute SDFT dislocation/luxation can be difficult, but palpation and observation during flexion and extension usually allow a diagnosis. Ultrasonography is the diagnostic imaging technique of choice . [3,6] Fibers of the tendon or granulomas were observed intrasynovially, and the position of the SDFT was stable. [15] Surgical correction (either through open reduction or endoscopically) has been used as the preferred treatment for the luxated tendon with an unstable displacement, either with or without the use of synthetic propylene mesh and post-operative immobilization in a cast for four to six weeks. Success rates vary, from return to athletic activity [7] or possible cast complications, i.e., laminitis, cast sore, cast breakage, secondary fracture, etc., and euthanasia. [14,15] Due to the chronicity of this case and our limitations of a surgical facility, non-invasive treatment methods, i.e., laser therapy, hydrotherapy, and medicinal approach, were used in this case. Laser therapy of a continuous striking beam of wavelength 810 nm and power of 4x 750 mW is projected over the inflammatory area. [16] Laser promotes cell proliferation, collagen synthesis, tissue remodeling, reduces inflammation, and aids in pain relief for both soft and hard tissue. [17,18] Steroids methylprednisolone acetate, triamcinolone acetonide, and dexamethasone are potent anti-inflammatory agents that are chondroprotective and improve cartilage health by interacting with cytoplasmic receptors and initiating up-regulation of prolonged effects. [19] A combination of both laser therapy and intra-bursal steroids gives beneficial results in reducing inflammation and improving lameness, which appears to be the ideal treatment in this case, considering all the limitations. However, a permanent solution is surgical stabilization of the subluxated tendon. 5. Conclusion Subluxation or luxation of the SDFT is a rare condition, but it can occur in playing horses. Diagnosing this condition is challenging. Even after diagnosis, the prognosis of surgical intervention is poor, as other complications like supporting limb laminitis and post-surgical infections are common. The horse with subluxation can be used for riding and breeding purposes. Conflict of interest statement There is no conflict of interest between authors 1 References 1 References [1] Baxter GM. Diagnostic approach to lameness. In: Manual of Equine Lameness. 2nd ed. West Sussex: Wiley-Blackwell; 2022: 65–82. [2] Baxter GM. Lameness of the proximal limb. In: Adams and Stashak’s lameness in horses. 7th ed. Hoboken, NJ: Wiley-Blackwell; 2020: 657–700. [3] Hinchcliff KW, Kaneps AJ, Geor RJ. Equine sports medicine and surgery: basic and clinical sciences of the equine athlete. 3rd ed. St. Louis, Missouri: Elsevier Saunders; 2024: 367–382. [4] Rice H, Brokken MT. Synovitis/capsulitis of the tarsocrural joint in horses. In: Aiello SE, Moses MA, eds. Merck Veterinary Manual. 11th ed. Kenilworth, NJ: Merck & Co; 2015: >>>> [5] Raes EV, Vanderperren K, Pille F, Saunders JH. Ultrasonographic findings in 100 horses with tarsal region disorders. Vet J., 2010; 186(2): 201-9. [6] Fubini SL, Auer JA, Stick JA, Kummerle JM, Prange T. Tarsus. In: Equine surgery. 5th ed. St. Louis, Missouri: Elsevier; 2019: 1710–36. [7] Wright I, Minshall G. Injuries of the calcaneal insertions of the superficial digital flexor tendon in 19 horses. Equine Vet J. 2011; (44): 136–42. [8] Smith RKW, Cauvin E. Ultrasonography of the hock. Equine. 2018; 2(6):188–93. [9] Whitcomb MB. Ultrasonography of the equine tarsus. Proc Am Assoc Equine Pract. 2006;52:13–30. [10] Anoushepour A, Eftekhari S, Masoudifard M. Evaluation of clinical and diagnostic imaging findings of bilateral superficial digital flexor tendon luxation in the tarsus of a gelding. Vet Res Forum. 2023; 14(10): 579–582. [11] Fubini SL, Auer JA, Stick JA, Kummerle JM, Prange T. Tarsus. In: Equine surgery. 4th ed. St. Louis, Missouri: Elsevier; 2012: 1402. [12] Bell BT, Baker GJ, Foreman JH, Abbott LC. In vivo investigation of communication between the distal intertarsal and tarsometatarsal joints in horses and ponies. Vet Surg. 1993; 22(4):289–292. [13] Scott SA, Breuhaus B, Gertsen KE. Surgical repair of a dislocated superficial digital flexor tendon in a horse. J Am Vet Med Assoc. 1982; 181(2):171–172. [14] Janicek JC, McClure SR, Lescun TB, Witte S, Schultz L, Whittal CR, Whitfield-Cargile C. Risk factors associated with cast complications in horses: 398 cases (1997–2006). Journal of the American Veterinary Medical Association. 2013 Jan 1; 242(1):93–8. [15] 1 Federici M, Fürst AE, Hoey S, Bischofberger AS. Outcome of conservative and surgical treatment for luxations of the equine superficial digital flexor tendon from the calcaneal tuber. Equine Vet. Educ. 2019; 31(1): 49–56. [16] Zielinska P, Nicpon J, Kielbowicz Z, Soroko M, Dudek K, Zaborski D. Effects of high intensity Laser therapy in the treatment of tendon and ligament injuries in performance horses. Animals. 2020; 10(8): 1327. [17] Pluim M, Reynolds A, McClure S. Adjunct Therapies for Tendon/Ligament Healing: Therapeutic Laser and Extracorporeal Shockwave Therapy. Vet Clin North Am Equine Pract. 2025; 41(2): 391–401. [18] Haussler KK, Manchon PT, Donnell JR, Frisbie DD. Effects of low-level Laser therapy and chiropractic care on back pain in Quarter horses. J Equine Vet Sci. 2020; 86: 102891. [19] McIlwraith CW. The use of intra-articular corticosteroids in the horse: What is known on a scientific basis? Equine Vet J, 2010; 42(6):563–571. 1 Federici M, Fürst AE, Hoey S, Bischofberger AS. Outcome of conservative and surgical treatment for luxations of the equine superficial digital flexor tendon from the calcaneal tuber. Equine Vet. Educ. 2019; 31(1): 49–56. Information & Authors Information Version history V1 Version 1 12 December 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Authors Affiliations Shehla Bokhari 0000-0003-0360-8380 [email protected] DHA Phase VI View all articles by this author Arslan Nazim DHA Phase VI View all articles by this author Muhammad Irfan DHA Phase VI View all articles by this author Arona Batool DHA Phase VI View all articles by this author Mazhar Iqbal DHA Phase VI View all articles by this author Metrics & Citations Metrics Article Usage 249 views 112 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Shehla Bokhari, Arslan Nazim, Muhammad Irfan, et al. Case Report Tarsocrural Synovitis and Superficial Digital Flexor Tendon Subluxation in a Polo Horse. Authorea . 12 December 2025. DOI: https://doi.org/10.22541/au.176556797.77444139/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. 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