HESTEFORSK Is 'Jumpers Knee' a clinical entity in horses? An investigation of patellar desmopathy as a cause of stifle lameness H-18-47-393

Orthopedic problems leading to lameness and pain is a major welfare issue in the general horse population. Hind limb lameness may be difficult to evaluate and diagnose. Missed diagnoses may lead to suboptimal or no treatment. Amongst human athletes, pain originating in the patellar tendon, known as 'jumpers knee', is a common clinical entity characterized by neovascularization and neoinnvervation of the ligament. To date, knowledge regarding the equine patellar ligaments is scarse, and the overall aim of this project is to characterize these structures and their potential relation to lameness. The first aim of the study is to characterize innervation and vascularization of normal patellar ligaments in sound horses, knowledge which to date is non-existent in veterinary medical literature, and which is of importance when interpreting diagnostic imaging findings. This work is in the process of being completed and published. Findings from the first part of the project is used to guide interpretation of patellar ligament ultrasonography in the second part of the study. Stifle ultrasonography is performed on a cohort of horses with known lameness status, evaluated by both subjective and objective lameness evaluation. Data collection for this part of the study is in the process of being completed. The third part of the study aims at establishing a model for inducing low-grade, temporary push-off lameness by injecting a small volume hypertonic saline into the middle patellar ligament. Upon establishing this model, a method for alleviating the lameness by diagnostic analgesia will be developed. Pilot-data for the lameness model is available, and this work as well as developing the diagnostic analgesia model is in process.

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'Jumpers Knee' is a well-described clinical entity in human athletes, characterized by nerve ingrowth and neovascularization of the patellar tendon leading to knee pain. To date, the role of the patellar ligaments in hind limb lameness in horses has not been scientifically investigated. By using objective motion analysis methods, we have detected a surprisingly high prevalence of 'push-off' hind limb lameness in sport horses, and pilot data from these horses suggests that this push-off lameness may indeed originate from pathology in the patellar ligament region. However, detailed anatomical descriptions of normal equine patellar ligaments are lacking, and similarly, there are no descriptions of normal versus abnormal diagnostic imaging findings regarding patellar ligament vascularisation. Therefore, we propose a multimodal investigative approach of the patellar ligament region, including anatomical, clinical and pathological studies of this particular region, to assess the potential role in equine hind limb lameness.