Chloe, a yearling female Quarter Horse, presented to the Equine and Farm Animal Hospital on July 10, 2005 for treatment and evaluation of a previously diagnosed right medial femoral condyle cyst. In May 2005, Chloe's owner noticed that she was lame while training on the lunge line and the referring veterinarian performed a lameness examination. Chloe was negative on hoof testers and fetlock radiographs were evaluated as normal so she was treated with 4 weeks of stall rest. One month later, Chloe showed no improvement in clinical signs so the referring vet expanded his lameness exam and took radiographs of more proximal joints and discovered a subchondral bone cyst in the right stifle. At that time, Chloe was referred to Cornell for further treatment.