Lameness associated with mixed pastern pathology in a Thoroughbred yearling

A yearling Thoroughbred filly presented to a yearling sale with right front lameness and radiographs demonstrating a large axial palmar OCF (osteochondral fragment) of the proximal P2 associated with the PIP (proximal interphalangeal) joint and no evidence of secondary osteoarthritis. A follow up lameness examination included diagnostic anesthesia, radiography and ultrasonography. The filly was 3 out of 10 lame right forelimb. There was pain on flexion of the distal limb and a positive distal limb flexion test. Lameness was localised to the pastern region. Radiography confirmed the OCF and an ultrasound examination revealed the large OCF with small hyperechoic fragments of bone evident in the middle scutum associated with the insertion of the axial palmar ligament of the PIP joint and SSL (straight sesamoidian ligament). More proximally there was a core lesion to the body of the SSL. Such large axial palmar OCF with a comprehensive lameness examination have not been reported yet. This provides the veterinarian information to give a balanced opinion for risk for sale and future athletic performance.