What is Bog Spavin?
Joints in horses behave similarly to those found in humans, in that they are comprised of bone and soft tissue which allow them to function to support the movements of the host. Bog spavin is a term applied to a disorder which applies to the development (or lack of) of the cartilage and bone in the tarsal (or hock) joint. This disorder is most common in young horses and is a result of inflammation which interferes with the development of the joint, either inherited or acquired.
Bog spavin in horses refers to inflammation of the synovial membrane. In this case, the membrane surrounds the tarsus, or hock, joint and can become long term. The inflammation of the hock joint is also known as bone spavin and curb.
Symptoms of Bog Spavin in Horses
The most common symptom is the visual observation of swelling or edema of the tarsocrural joint on both sides of the hock. The enlargement of this area will be located mostly on the middle back surface of the hock. The edema may fluctuate and, if examined by touch or if pressure is applied to one side of the edema, the other side will increase in size. Additionally, heat and pain will likely be most noticed on the front surface of the hock.
- Swelling of the hock
- Heat in the hock
- Pain in the hock
While this condition is more frequently found in young horses, it can show up in several ways:
- Poor conformation (straight hocks, sickle hocked, cow hocked)
- Nutritional deficiencies
- Injury or other trauma
- Can be bilateral as well as unilateral
Some of these types are treatable while others are not. If the type of bog spavin is inherited, it cannot be successfully treated.
Causes of Bog Spavin in Horses
The enlargement or swelling has no bone involvement, it only involves the synovial membrane which is a membrane that lies within and surrounds the hock joint that permits smooth and flexible movement of the joint. Bog spavin, as defined above, is a long term, low-grade inflammation of this membrane over time. The inflammation will cause fluid to collect mostly on the middle surface of the hock with lesser swelling occurring on each side of the hock, near the back. The associated swelling won’t necessarily cause the horse to be lame and, if uncomplicated, will not likely interfere with your horse’s usefulness. You should be aware that it will, however, come and go in weanlings and yearlings. If excessive swelling exists, the horse can experience mechanical lameness over time as well as a change in gait as the flexibility of the joint decreases. Other causes of bog spavin in horses:
- Stresses cause straight hocks, sickle hocks or cow hocks
- Lameness in another limb
- Intense training
- Nutritional deficiencies (phosphorus, calcium, vitamin A or vitamin D)
- Zinc poisoning
Other causes of the fluid accumulation noted above can also be:
- Osteochondrosis in young horses
- Blood in the joint cavity itself
Diagnosis of Bog Spavin in Horses
Your veterinarian will need to do a physical examination and his evaluation will likely include x-rays of the joint. Your veterinarian will also need a complete medical history from you, the owner or handler, to complete the assessment. Ultrasound, CT scanning, scintigraphy (bone scan) and MRI are also imaging methods that will help in the assessment process. Another method of imaging, while more invasive than those listed above, that will be helpful in this evaluation is the arthroscopy which will involve the use of an arthroscope to take a look inside the joint.
Treatment of Bog Spavin in Horses
Once the cause has been determined, treatment can be offered with a few options, depending on the severity of the condition. The fluid excess that exists within the joint membrane can be removed by your veterinarian using a needle and syringe. Medication therapy will accompany this method. Corticosteroid injections to the joint are also successful in the short term for relief. An evaluation of your equine’s diet may indicate changes should be made that can include supplementation. Compression bandaging of the leg may be necessary, along with rest and exercise restriction. If bone and cartilage are involved, surgery using an endoscope may be used.
Recovery of Bog Spavin in Horses
Before any treatment is recommended and initiated, the underlying cause must be determined and eliminated if at all possible.
If your veterinarian determines the cause to be nutritional, then a careful assessment of your horse’s diet will be needed and, once the deficiency is determined, adjustments made to supply your horse with what is missing to avoid repeat episodes.
If the horse is young, the bog spavin will frequently resolve itself with appropriate rest and compression bandaging of the joint.
Surgical drainage may be necessary which will likely be supported by injections of anti-inflammatory medication into the joint. Any surgical option will require restricted turnout for several weeks as a postoperative regimen. Afterwards, expect to be able to return your horse to normal paddock turnout but a slow return to work should be exercised. If the condition is related to heredity (and it generally is) and poor conformation, the symptoms will likely return periodically.
The periodic return of bog spavin without lameness is a very real possibility that will cause the swelling to be a cosmetic concern more than a functional one. This cosmetic concern should be accepted as a long-term result of the condition that has no option of total and complete resolution.