33rd Annual Scientific Meeting proceedings

Subchondral cystic lesions (SCL) of the medial femoral condyle (MFC) are a common cause of lameness in young horses. With pre-sales screening radiographs lesions are often detected Asymptomaticly. Conservative treatments have been recommended in asymptomatic cases.

This report documents 4 asymptomatic horses, treated for subchondral lucencies or cyst-like lesions, managed conservatively via confinement and intra-articular injections with 10mg of Triamcinolone Acetonide (TCA) into the medial femoral tibial joint (MFTJ). They all became acutely lame on the treated limbs developing effusion of the MFTJ and the femoropatellar joint (FPJ). All cases were non-septic. At the time of surgery, no joints had radiographic changes within the FPJ. On arthroscopic examination the MFTJ and FPJ had areas of detached cartilage. The lesions had the appearance of acute delamination of articular cartilage leaving an underlying, pale, avascular subcondral bone plate below. Lesions were located on the distal underside of the patella, the lateral and medial trochlear, and the load bearing surface of the MFC.

These cases received safe therapeutic doses of TCA. This case series documents the previously unreported iatrogenically induced damage to healthy cartilage of yearlings following attempted medical treatment of MFC subchondral cyst-like lesions. This series shows that there are deleterious effects of TCA on development of healthy juvenile cartilage. There is no justification in treating MFC subchondral bone lucencies or early cyst-like lesions with corticosteroids without an established cyst lining. Therefore, treatment of SCL using corticosteroids limited to arthroscopically guided injection directly to the cyst lining rather than the intra-articular space.