Bone spavin: Bone spavin is bone enlargement (growth) in a horse's hock caused by osteoarthritis. Osteoarthritis is the type of arthritis occurring after cartilage wears away. Reasons for horses to suffer bone spavin could be conformation, or a lifestyle with excessive:
- pounding or stress (such as in Standardbreds or jumpers);
- flexion (dressage horses);
- stops, starts, and turns (reining horses);
Osselets: Often a precursor to bone spavin, osselets is defined as inflammation of the periosteum (bone lining) in the fetlock joint. Eventually osselets leads to arthritis. Much like bone spavin, horses which often suffer from this suffer from excessive concussion to the frontlegs. Short, upright pasterns may predispose a horse to this because this type of conformation promotes more pounding in the front legs. Early stages of osselets is called “green osselets” – hot, soft swelling. If inflammation damages the cartilage of the joint, it will become chronic and permanent.
Bog Spavin: Similar to bone spavin, bog spavin is a chronic, soft swelling in the hock resulting from excessive fluid in the joint capsule, but in this case the horse may not be lame. This can be caused by an injury or a strain to the tendons. Once the injury heals, a soft swelling stays which is painless. If the strain persists, usually due to poor conformation, it may develop into arthritis.
Fistulous withers: Fistulous withers is the inflammation of the supraspinous bursa, the major fluid-filled sac which protects vertebrae in the withers region of horses. Learn more about fistulous withers at The Merck Veterinarian Manual.
Splints: 'Splints' is a condition of inflammation from injury to either the periostium (lining of the bone) of the splint bone in a horse's front leg, or to the ligament binding the splint bone to the cannon bone. Often in conjunction with the inflammation will be a bone 'lump' from the calcium attempting to rebuild. Trauma, overworking or concussion can cause splints. Trauma can be a kick from another horse, or a blow of some sort to the leg; overworking a young horse puts undo strain on the ligaments, and concussion - such as jumping - can also cause this injury.
Ringbone: Ringbone is the common term for a bony growth in a horse's coffin joint or pastern. It's actually osteoarthritis, which is degenerative arthritis in the joints. Sometimes the bony growth occurs around the entire bone, which is where the term 'ringbone' comes from. Causes of ringbone can be excess tension on the ligaments, trauma, conformation or poor trimming and shoeing practices.