Horse Bone Spavin

horse bone spavin

Horse bone spavin is a common condition that can cause serious lameness in the hock (tarsus). It is a form of degenerative joint disease affecting the distal tarsal joints — the central and the distal intertarsal joints. It is characterized by excessive and repeated compression of cartilage in these joints, resulting in narrowing of the joint spaces, which eventually fills with bone. It is often exacerbated by rotational forces in the hock and shearing stresses on the distal hock bones, especially the calcaneus. It is also sometimes aggravated by excessive flexion of the hind feet, as in jumping, and sudden stops or turns in western events, such as reining. Bone spavin can affect all breeds and types of horses, but it is more prevalent in sports requiring repetitive hock flexion, stress or shearing of the calcaneus.

Several conformational abnormalities predispose to bone spavin, particularly those that result in uneven loading of the hocks. Poor trimming or shoeing can also contribute to this problem. Some disciplines, such as dressage and jumping, tend to produce a great deal of hock flexion, shearing stresses or bending of the calcaneus, which can contribute to bone spavin.

In addition to the excessive bone formation, which is a characteristic feature of the condition, there may be evidence of pain and inflammation in the hock joints. Some horses will be lame, especially when ridden or lunged, while others show only slight signs of discomfort and are able to continue their work programs.

A veterinary examination will include the use of a flexion test, which is a quick, non-invasive way to determine whether a horse has DJD of the hock, including bone spavin. The veterinarian will lift the foot and sharply flex it for one to two minutes to see if the horse becomes lame. If the flexion test is positive, further palpation or radiography of the hock joint and sheath may be required to confirm the diagnosis.

Treatment of a horse with bone spavin aims to reduce pain and inflammation, control the progression of the condition, and improve function in the affected joint. Non-steroidal anti-inflammatory drugs are the first line of defense, with phenylbutazone (‘bute’) being the most commonly used drug.

Other joint medications, such as hyaluronic acid and Adequan, can be useful in managing the condition if it is mild to moderate. However, they may not be effective if the condition is advanced.

A bisphosphonate, such as Tiludronic acid (tradenames Tildren and Equidronate), has shown to be very effective in treating horse bone spavin. This medication is injected into the lower tarsal joint, and it works by reducing calcium accumulation in the cartilage and decreasing the pressure on the underlying soft tissues. It is important to check association rules before using this drug, as it may be banned in competitions. Surgery to remove the cartilage and fuse the joint is an option for severe cases of bone spavin. However, this is an invasive procedure with mixed results.