Straight sesamoidean ligament desmopathy commonly occurs with proximal interphalangeal joint osteoarthritis

Proximal interphalangeal joint osteoarthritis (PIPJ OA) is a common cause of poor performance in the equine athlete; however, the supporting soft tissue structures surrounding the joint are seldom evaluated. Straight sesamoidean ligament injuries have been previously hypothesised to be concomitant with PIPJ OA; however, the frequency of these lesions coinciding with PIPJ OA has not been fully investigated.

To investigate the prevalence of straight sesamoidean ligament desmopathy (SSLD) in horses presenting with PIPJ OA.

Retrospective clinical study.

Horses presenting with PIPJ OA and diagnostic imaging of the surrounding soft tissue structures with either ultrasonography or magnetic resonance imaging (MRI) were identified and enrolled. The images were reviewed by two board-certified radiologists. SSLD was graded as absent, mild, moderate, or severe. Osteoarthritis was similarly graded. Spearman's rank correlation was utilised to assess the correlation between the severity of PIPJ OA and SSLD.

Fifty-eight horses (60 limbs) with PIPJ OA met the inclusion criteria and of these 28 (46.7%) were concurrently diagnosed with SSLD. There was a significant, fair positive correlation between PIPJ OA severity and SSLD severity (p = 0.015, r = 0.401). There was no correlation between lameness severity and the presence of SSLD in horses with PIPJ OA (p = 0.37, r = 0.1757).

Retrospective study with reliance on medical records. Selection bias due to the inclusion of only cases with both radiographic and soft tissue assessment.

SSLD frequently occurs alongside PIPJ OA, and there is a fair and significant correlation between SSLD severity and PIPJ OA severity. Evaluation of the soft tissue structures of the pastern region may be beneficial in horses with more marked radiographic changes, or those that do not respond to treatment as expected.