Subchondral cystic and related lesions affecting the equine pedal bone and stifle.

Twenty-nine horses were examined over a period of 8 years and found to have cystic lesions in the stifle (14 cases) or pedal bone (15 cases). The lesions are described and illustrated with radiographs. In the stifle 12 lesions were found on the femoral condyles (11 medially and one laterally) and 10 were typical subchondral cysts. One lesion was observed in the tibia and 3 in the patella. Bone cysts wee found unilaterally in the pedal bone (14 in the forelimbs and one in the hindlimb). All but 2 of the horses with lesions in the stifle or pedal bone were lame. The only treatment was rest. For the stifle lesions, the prognosis was reasonable for young horses but poor for those over 4 years of age; for the pedal bone lesions the prognosis was guarded. Trauma is advanced as the most likely major aetiological factor.