Lameness Associated with Mineralization of the Central Tarsal Bone and a Small Osseous Cyst-Like Lesion in Two Sport Horses

The clinical features, response to local analgesia, and imaging findings of two mature sport horses with lameness associated with abnormal mineralization of the dorsal aspect of the central tarsal bone and a small osseous cyst-like lesion are described. Although the radiological findings and the lesions identified using magnetic resonance imaging were similar, the lameness characteristics and responses to perineural analgesia differed. One horse failed to respond to treatment and was retired. The second horse was humanely destroyed. Postmortem examination confirmed the presence of an osseous cyst-like lesion distal to the subchondral bone plate of the central tarsal bone and extensive dense cancellous bone extending one-half the dorsoplantar depth of the bone.