Beyoncé, a bay Thoroughbred filly owned by Patricia and Will Lalor, whose barn is based in Clonmel, Ireland, was destined for a show jumping career. But at 16 months of age she was diagnosed with a condition known as osteochondritis dissecans (OCD), which had developed in her left and right knees. It is a common orthopaedic developmental disease in many species including humans, and results in separation of the articular cartilage from the underlying bone in the joints. Depending on the breed, it can affect 10 to 30 percent of the equine population.