Western performance horses with fetlock lameness demonstrate radiographic evidence of chronic exercise remodelling.

Abstract

Background: Pathological changes of the fetlock joint are well documented in Thoroughbreds, but little information is available describing the common radiographic findings in western performance horses with fetlock lameness.

Objectives: To describe radiographic findings in western performance horses with fetlock lameness. It was hypothesised that the degree of lameness would correlate with the severity of radiographic findings.

Study design: Retrospective case series.

Methods: Retrospective review (2012-2022) of horses with lameness isolated to the fetlock joint via intra-articular analgesia and corresponding radiographs was included. Signalment, lameness, flexion, and effusion grades were recorded. Radiographs were evaluated for presence, severity, and location of pathology. Subjective radiographic severity scores were assigned. Correlations between outcome parameters were evaluated with Spearman's correlation coefficient. Statistically significant changes in median lameness grades for each radiographic abnormality were determined using the Wilcoxon Rank Sum test.

Results: Ninety cases met inclusion criteria. Radiographic lesions were identified in 96.7% of cases. Distal cannon bone sclerosis, periarticular osteophytes, increased soft tissue opacity, proximal phalanx (P1) sclerosis, and subchondral bone (SCB) defects were most common. Horses with SCB cysts (median 3; Interquartile range (IQR) 2.25-3.75; p < 0.05), P1 fissures (median 3; IQR 3-3; p < 0.05), or proximal P1 sclerosis (median 2; IQR 2-3; p < 0.05) had significantly higher median lameness grades. No significant correlation was established between overall radiographic score and lameness grade (r = 0.16, p > 0.05).

Main limitations: Outcome parameters were not captured for every horse due to retrospective design. Diagnostic analgesia has inherent limitations with specificity and interpretation of results. Using multiple clinicians may have led to inconsistencies in lameness grade, flexion response, and improvement after diagnostic analgesia.

Conclusions: Horses in this study demonstrated changes associated with chronic exercise-induced remodelling and degenerative joint disease. While the degree of lameness did not correlate with the overall radiographic score, certain radiographic findings-P1 sclerosis, SCB cysts, and P1 fissures-were correlated with a higher degree of lameness.