1. Bone Spavin: Bone spavin is a condition that affects the hock joint, which is located just above the knee. It is caused by the formation of bony growths on the bones of the hock, which can cause pain, inflammation, and lameness.
2. Bog Spavin: Bog spavin is a condition that causes a soft, fluid-filled swelling in the hock joint. It is often associated with bone spavin and can also cause lameness.
3. Capped Hock: Capped hock is a condition that affects the point of the hock, where the calcaneus bone meets the tibia and fibula. It is caused by inflammation of the bursa, a fluid-filled sac that helps to cushion the joint. Capped hock can cause pain, swelling, and lameness.
4. Splint: A splint is a bony growth that forms on the cannon bone, which is the long bone below the knee. Splints can be caused by trauma or overuse, and can cause pain, swelling, and lameness.
5. Tendon or Ligament Injury: A strain or tear to a tendon or ligament in the hock joint can also cause pain, swelling, and lameness.
If your horse is limping and has a small, hard bump at the back leg just above the knee, it is important to have your horse evaluated by a veterinarian to determine the exact cause of the lameness and to receive appropriate treatment.