Osteoarthritis of the coxofemoral joint in 24 horses: Evaluation of radiography, ultrasonography, intra-articular anaesthesia, treatment and outcome

BackgroundFew case reports describe equine coxofemoral joint osteoarthritis (CFJOA).ObjectivesTo evaluate diagnostic findings and outcome of horses with CFJOA and to provide a score facilitating radiographic assessment.Study designRetrospective case series.MethodsHistory, clinical signs, ultrasonographic, radiographic and intra-articular anaesthesia findings, treatments, outcome, and necropsy results of horses with CFJOA presented between 2002 and 2023 were collated. Radiographic findings were categorised to develop a radiographic score which was applied by two masked examiners. Intra- and inter-observer reliability was determined using weighted Cohen's kappa (C kappa) and the correlation between radiographic and ultrasound findings via Spearman correlation coefficient.ResultsThe study included 24 horses (median age 14 years). Most of them (20/24) were chronically lame. Frequent clinical signs included unilateral gluteal muscle atrophy (18/21), lengthening of the stride of the affected limb (13/19) and locomotion on three tracks (13/20). Both imaging modalities enabled evaluation of periarticular osteophytes (correlation coefficient r = 0.64; p = 0.003). Additionally, radiography allowed detection of irregular joint spaces, subchondral bone opacity changes and femoral head flattening/tapering. Inter-observer (C kappa = 0.846) and intra-observer (C kappa = 0.853 and C kappa = 0.842) agreement was excellent. If treated, mostly intra-articular corticosteroids were administered (16/18). Nine horses were euthanised immediately or during follow-up examination. Post-mortem, the Ligamentum capitis ossis femoris was commonly found ruptured. All surviving horses remained lame.Main limitationsRetrospective analysis of clinical records and subjective outcome assessment based on owner follow-up with potential recall bias. Due to overall disease severity, associations between different grades of clinical findings, radiographic abnormalities and outcome could not be evaluated.ConclusionsTypical clinical signs may indicate CFJOA. Standardised evaluation of ventrodorsal radiographs allows a comprehensive diagnosis. Postmortem findings suggest joint instability as a possible causative factor that may contribute to the poor prognosis and resistance to medical therapy of the disorder.