Bone Spavin (Distal Hock) Arthritis in Horses

Bone spavin is the result of excessive wear and tear on the cartilage in the hock joints that causes inflammation. Inflammation causes toxins to further degrade cartilage to the point where the body can no longer repair itself as quickly as it is damaged. Once the cartilage has eroded, the ends of the bones develop bony protrusions (exostoses) to stabilize the joint. With no cushioning cartilage left to protect them, these bony spurs rub against each other and the ends of the bones, causing pain and lameness.

Any horse showing signs of mild to moderate lameness requires prompt veterinary care to identify an underlying cause. Bone spavin is a progressive disease. Symptoms vary with the severity of the cartilage erosion, but most cases show mild lameness when first diagnosed. Symptoms also vary as the horse warms up during exercise (seem to improve) or are worked excessively (seem to worsen).

Bone spavin is a common cause of lameness in horses. Horses that compete in activities requiring excessive compression and rotation of the hock joints including western performance, rodeo, jumping, dressage, and pulling events are most at risk. Horses with improper conformation such as those with sickle hocks, cow hocks or excessively straight hocks are also at risk. Young horses with abnormal development of the hock bones are vulnerable to juvenile spavin.

Underlying causes of cartilage erosion include:

• Excessive compression and rotation of the hock joints
• Uneven loading of the limb during motion
• Improper shoeing
• Conformation defects
• In cases of juvenile spavin, malformation of the cuboidal bones due to osteochondrosis or incomplete ossification during development

Lameness is often intermittent, especially in the hind limbs and especially when on a circle.

If bone spavin is suspected, or if lameness occurs, veterinary attention is required. Diagnostic tools include:

• Physical exam
• Gait examination
• Intra-articular local analgesia to determine the affected joint
• Diagnostic imaging, including X-rays and ultrasound
• Specialized diagnostics, such as scintigraphy (bone scan)

Bone spavin is irreversible. Treatments aim to slow progression, manage pain, and reduce lameness. Treatments include:

• Non-steroidal anti-inflammatory drugs
• Corticosteroid injections in the lower hock joints
• Altered performance demands
• Joint support medications
• Changes in shoeing or trimming
• Light, consistent exercise to prevent stiffness
• Nutraceuticals
• Full or partial neurectomy to prevent pain signals from reaching the brain

Some practitioners may recommend complementary therapies, including:

• Therapeutic ultrasound
• Acupuncture
• Chiropractic
• Cold lasers
• Electromagnet therapies
• Extracorporeal shock wave therapy

In severe or intractable cases, treatment includes arthrodesis - the fusion of the joint. The aim is to fuse the bones to prevent rubbing and therefore pain.

Note: NSAIDs are illegal in competition as are some other treatments. Caution and research are required for those wishing to continue to compete while in treatment for arthritis.

Prognosis is variable and depends on the degree of damage to joints and bones when diagnosed, the size of the horse, the performance demands, and the choice of treatment. Some horses respond well to intra-articular injections or arthrodesis and are able to return to sport or work after a recovery period (up to 1 year). For some horses, pain management and retirement from sport or work are required. In severe cases, bone spavin results in the horse not being able to tolerate being ridden. Horses with juvenile spavin must be carefully managed in order to prevent further joint disease as they start their ridden careers. Some horses with juvenile spavin may never have an athletic career due to soundness issues.

Possible strategies to minimize the risk of bone spavin include:

• Prompt veterinary assessment of any lameness, even mild
• Modified performance demands in horses with early symptoms

Bone spavin is a common cause of lameness in horses, particularly those used for sport.

• Pain medication
• Anti inflammatories
• Rest or retirement from sports that require extreme use of the hock joint
• Intra-articular injections
• Nutriceuticals
• Proper shoeing
• Light, consistent exercise to prevent stiffness
• Complementary therapies
• Neurectomy
• Arthrodesis (joint fusion)