Detection of early osteoarthritis in the centrodistal joints of Icelandic horses: Evaluation of radiography and low‐field magnetic resonance imaging

REASONS FOR PERFORMING STUDY: Validated noninvasive detection methods for early osteoarthritis (OA) are required for OA prevention and early intervention treatment strategies. OBJECTIVES: To evaluate radiography and low‐field magnetic resonance imaging (MRI) for the detection of early stage OA osteochondral lesions in equine centrodistal joints using microscopy as the reference standard. STUDY DESIGN: Prospective imaging of live horses and imaging and microscopy of cadaver tarsal joints. METHODS: Centrodistal (distal intertarsal) joints of 38 Icelandic research horses aged 27–29 months were radiographed. Horses were subjected to euthanasia approximately 2 months later and cadaver joints examined with low‐field MRI. Osteochondral joint specimens were classified as negative or positive for OA using light microscopy histology or scanning electron microscopy. Radiographs and MRIs were evaluated for osteochondral lesions and results compared with microscopy. RESULTS: Forty‐two joints were classified OA positive with microscopy. Associations were detected between microscopic OA and the radiography lesion categories; mineralisation front defect (P