Spavin in Horses

By Deidre M. Carson, BVSc, MRCVS & Sidney W. Ricketts, LVO, BSc, BVSc, DESM, DipECEIM, FRCPath, FRCVS.

'Spavin' is a common condition in ponies and horses of all ages. There are two forms of spavin - bone spavin and bog spavin. Both affect the hock.

What is bog spavin?

spavin-1Bog spavin is excessive fluid in the largest of the hock joints. This can result in slight or severe enlargement of the hock. One or both hocks may be affected. It is more commonly seen in younger horses, although it can occur at any age. The increase in fluid can be the result of injury (trauma), degeneration of bone or cartilage in the joint (OCD), or joint infection (septic arthritis).  There may be associated lameness that can range in degree from mild to severe depending on the cause.

Can bog spavin be treated?

Depending on the cause of the bog spavin, several treatments are available and you should ask your veterinarian to make a diagnosis and for advice. If the condition is caused by traumatic injury (most commonly a 'strain') and there is no associated lameness, rest and some anti-inflammatory medication is all that is needed. If the joint remains enlarged it may be necessary to drain the joint of excessive fluid and to inject corticosteroids into it. This should only be considered if fractures, OCD and infection have been ruled out, by your veterinarian, with the use of radiographic (x-ray) examinations, joint fluid analysis and blood tests. See our handouts on osteochondritis dissecans (OCD) and arthritis. If the horse or pony is lame, it should be rested and treatment postponed until the cause of lameness and spavin is determined. Treatment will entirely depend on the diagnosis. Box rest, joint medication or surgery may be recommended. Your horse may or may not need to be referred to a specialist center if surgery is required or the joint infected.

What is bone spavin?

Bone spavin is degenerative, non-septic arthritis of the smaller hock joints. It is more often seen in older horses and ponies and is a common cause of hindlimb lameness. The lameness can range from mild stiffness with toe dragging to quite severe. It may affect one or both hind limbs. Radiographs (x-rays) taken of affected hocks can demonstrate a wide range of bone degeneration and damage that does not always directly correspond to the degree of lameness seen.

Can bone spavin be treated?

Treatment for bone spavin, being a form of arthritis, aims to reduce pain either by reducing inflammation or reducing movement in the joint(s).  In some cases there is a good response with anti-inflammatory medication such as phenylbutazone, while continuing exercise. In others it may be necessary to inject corticosteroid medication into the affected joints to reduce inflammation. Alternatively, strong irritant solutions have been injected into the affected joints to try to inflame them sufficiently to heal solid (ankylose), thereby abolishing painful movement. These small hock joints are not 'high movement' joints and the horse does not miss their ability to move.

Surgical treatments are also directed at ankylosing the joints. Once the joints are fused, no movement is possible and the lameness usually disappears. This type of treatment can take up to a year to settle and to know if it has been helpful.

What is a spavin test?

A traditional spavin test is conducted in three stages:

1. The horse is trotted in hand in a straight line to determine the degree of lameness, if any, and the leg involved.

2. The lame hind leg is held up in a flexed position for up to two minutes.

3. The horse is trotted again to see if the degree of lameness has been made any worse.

If the horse is not lame, the test is repeated with the other leg. When the horse is made lame (or more lame) by flexion test it is said to be a positive spavin test. The name is often misleading as many different conditions affecting other joints or areas of the hind leg can cause a positive result and the test is certainly not specific for bone spavin.

As with all disease conditions, diagnosis is the first step to successful treatment and management. Ask you veterinarian for advice.