Fetlock Lameness in Western Horses: Radiographs Reveal Chronic Bone Remodelling

Western Performance Horses with Fetlock Lameness Demonstrate Radiographic Evidence of Chronic Exercise Remodelling

Gabrielle Solum; Elizabeth Acutt; Sherry A. Johnson; Tianjian Zhou; Erin K. Contino; Josh R. Donnell; Alan Donnell; David D. Frisbie

Background

Fetlock joint pathology is a well-recognised cause of lameness in Thoroughbred racehorses, but comparatively little is known about radiographic changes associated with fetlock lameness in western performance horses. These horses experience different athletic demands yet are subject to repetitive cyclic loading of the fetlock joint. The study aimed to characterise radiographic findings in western performance horses with lameness localised to the fetlock joint and to determine whether lameness severity correlates with radiographic severity.

Methods

This retrospective case series reviewed medical records from 2012–2022 of western performance horses with lameness localised to the fetlock joint via intra-articular analgesia (≥70% improvement). Ninety horses met inclusion criteria. Signalment, lameness grade (AAEP scale), flexion response, and effusion were recorded when available. Standard fetlock radiographs obtained within 90 days of examination were evaluated by a board-certified equine radiologist blinded to clinical data. Radiographic abnormalities were recorded by type, location, and severity, and a subjective whole-joint radiographic severity score was assigned. Statistical analyses assessed associations between radiographic findings, lameness grade, age, and overall radiographic severity.

Results

Radiographic abnormalities were identified in 96.7% of cases. The most common findings were distal third metacarpal/metatarsal bone sclerosis, periarticular osteophytes, increased soft tissue opacity, and proximal phalanx sclerosis, most frequently affecting the medial aspect of the joint. Overall radiographic severity did not significantly correlate with lameness grade. However, specific lesions—subchondral bone cysts, proximal phalanx fissures, and proximal phalanx sclerosis—were associated with significantly higher median lameness grades. Age showed weak correlations with lameness grade, periarticular osteophytes, and overall radiographic score.

Limitations

The retrospective design limited consistency in clinical examinations, diagnostic analgesia, and outcome data collection. Multiple clinicians contributed to lameness grading, introducing subjectivity. Radiographic interpretation relied on a single radiologist, and advanced imaging or arthroscopic confirmation was not available. Not all radiographs were obtained on the same day as diagnostic analgesia, potentially affecting interpretation.

Conclusions

Western performance horses with fetlock lameness commonly demonstrate radiographic changes consistent with chronic exercise-induced osseous remodelling. While overall radiographic severity does not correlate with lameness grade, certain findings—particularly proximal phalanx sclerosis, fissures, and subchondral bone cysts—are associated with greater lameness. Recognition of these lesion patterns may aid clinicians in diagnosis, monitoring disease progression, and managing workload in western performance horses.

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