Synoviocoeles associated with the tarsal sheath: description of the lesion and treatment in 15 horses

Reasons for performing study: To describe the presentation, clinical, ultrasonographic and endoscopic features associated with a defect in the tarsal sheath wall, to define the cavity created and to describe a method of treatment. Hypothesis: So called ‘false thoroughpins’ can be caused by defects in the tarsal sheath wall creating a one way valve effect, removal of which could be therapeutic. Methods: Case records and diagnostic images of horses with synoviocoeles associated with the tarsal sheath were reviewed retrospectively and follow‐up information obtained. Results: Synoviocoeles were diagnosed in 15 horses. All were managed similarly and 10 horses had clinical resolution and returned to work. Conclusion: Terminology previously used to describe lesions involving the tarsal sheath does not define accurately the condition described and the term synoviocoele is recommended. Endoscopic enlargement of the sheath wall defect produced good clinical results in 10/15 horses. Potential relevance: Clinicians should include synoviocoele in the list of differential diagnoses of fluid filled cavities associated with the tarsal sheath and should consider endoscopic surgery as a treatment modality.