Osteo-arthritis of the hock is commonly called spavin. It manifests itself by chronic mild lameness of the hind limbs. In most cases, it is bilateral. Horses that are the most affected are those who perform in show jumping, western riding and those that have conformation abnormalities in the hind limbs. In more severe cases a deformation and enlargement of the hock can be seen, however often only x-rays will show the new bone.