Patella tendinopathy Zoobiquity — What can we learn from dogs? ☆ Michael J. Dan a, ⁎, James Crowley a , David Broe a , Mervyn Cross b , Chris Tan a , William R. Walsh a a The Surgical and Orthopaedic Research Laboratory, Prince of Wales Clinical School University of NSW, Randwick, NSW, Australia b The Stadium Sports Clinic, Sydney, Australia article info abstract Article history: Received 10 September 2018 Received in revised form 30 October 2018 Accepted 10 November 2018 Background: Patella tendinopathy is an overuse condition. Pathogenesis and identification of intrinsic risk factors have largely eluded the orthopaedic world. The cranial cruciate ligament (CrCL) in dogs is the equivalent to the human anterior cruciate ligament (ACL). We report the effect of two canine proximal tibial osteotomy procedures in the veterinary literature on patella tendon moment arm and describe the biomechanical rationale for a tibial tubercle osteotomy for treatment of patella tendinopathy in the human. Methods: A literature review of studies reporting clinical complications of TTA and TPLO to form an observational animal cohort study in dogs. Results: The veterinary literature reports an overall clinical complication rate of up to 61% for TTA and up to 50% for TPLO respectively. Complications associated with the extensor mecha- nism of the knee are b 1% for TTA compared to 1.9–19% for TPLO. Radiographic thickening of the patella tendon and tendinopathy is seen in one to 80% of TPLO cases. The TPLO decreases the moment arm of the extensor mechanism meaning increased force is required in the patella tendon to achieve the same torque when compared to the TTA which increases the efficiency of the extensor mechanism. This difference may account, in part, for the post-operative compli- cations reported to the patella and patella tendon following TPLO. Conclusion: This observational animal cohort study demonstrates a biomechanical rationale for investigating diagnostic and potential treatment options, including a tibial tubercle osteotomy, for patella tendinopathy in humans based on this principle. © 2018 Elsevier B.V. All rights reserved. 1. Introduction Patella tendinopathy is an overuse condition most commonly affecting jumping athletes, with a reported incidence of greater than 50% for volleyball and basketball players and an overall incidence of 14% [1]. Patella tendinopathy is characterised by pain and tenderness at the distal pole of the patella [2]. There is a 53% incidence of retirement due to patella tendinopathy vs seven percent of other athletes retiring due to injury [3]. Risk factors for the condition are either extrinsic that are external to the athlete or intrinsic which are internal to the athlete. Extrinsic risk factors include increased training volume and harder training surfaces [4–6]. Intrinsic risk factors include hamstring and muscle tightness [7], abnormal leg lengths and loss of medial arch of the foot [5]. Previous studies have failed to show a sta- tistical difference in the morphology of the patella of those with and without patella tendinopathy [8,9,4]. These studies have ex- The Knee 26 (2019) 115–123 ☆ Declarations of interest: none. ⁎ Corresponding author at: Surgical & Orthopaedic Research Laboratories, Prince of Wales Hospital, Level 1, Clinical Sciences Building, Randwick, NSW 2031, Australia. E-mail address: michaeldan@hotmail.com (M.J. Dan). https://doi.org/10.1016/j.knee.2018.11.010 0968-0160/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect The Knee