Bog Spavin

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Also Known As

Hock joint swelling


Bog spavin is a condition where a soft swelling occurs on the medial surface of the hock joint resulting from excessive fluid within the joint capsule. It is usually seen as two distinct swellings, one on the back and the other on the front of the hock joint. Joint fluid in the top joint increases in the sack and pushes out so it is visible.

When a horse develops bog spavin, it is usually lame only if the condition is caused by stress. If caused by accidental trauma, the horse will be sound again as soon as the joint heals. Most bog spavins heal without treatment. Occasionally a more serious joint problem known as osteochondritis dissecans (OCD) occurs. Osteochondritis dissecans requires a veterinarian's attention to prevent further damage to the joint.


  • Soft swelling on the inside front of the hock with a smaller swelling on the outside
  • Lameness, although not always
  • Heat and pain if caused by stress


Bog spavin often occurs in horses with poor conformation. If the hocks are too straight when viewed from the side, instead of being directly under the buttock, the bog spavin may be due to stress resulting from the poor conformation.

Bog spavin can also be caused by severe injury to the hock or from strain caused by quick stops and turns when the weight is suddenly put on the hock. This often happens with stallions that are into playing and rearing as they interact with other horses or with handlers.

If the big hinge joint in the hock is injured, the joint capsule works overtime to produce extra lubricating fluid. This results in soft swellings on the front inside part of the hock and sometimes two smaller swellings on each side of the hock. Once stretched, the joint capsule stays that way, leaving the horse with a permanent enlargement.

Nutritional deficiencies may also cause bog spavin.


Working with horses to minimize stress or injury to the hock joints is the best prevention. If the condition is the result of hereditary conformation, not much can be done beyond careful exercising and using anti-inflammatory drugs to decrease inflammation and prevent fluid build-up. A pressure bandage may help minimize the swelling.

If the problem is more than a slight strain on the joint capsule with mild inflammation and swelling, it may indicate a more serious joint problem known as osteochondritis dissecans. An x-ray examination will help determine if osteochondritis dissecans exists in the hock joint.

If nutritional deficiencies cause the bog spavin, a careful analysis of the horse's diet is necessary to determine what is missing from the diet and provide the necessary supplements to insure that the condition does not re-occur.


Veterinarians have many factors to consider in order to determine the cause of bog spavin and advise the best treatment.

Most bog spavins heal on their own, and the horse is left with a small, painless swelling. In a young horse, the swelling may disappear altogether if the strain that caused it was a one-time injury and not due to poor conformation.

If the joint stays inflamed and the swelling is hard and tense, arthritis may develop in the joint, causing lameness, in which case, anti-inflammatory injections will help with the swelling and a veterinarian may prescribe corticosterioids in combination with other treatments to improve cartilage health and reduce substances that degrade the cartilage.

Two or three injections of anti-inflammatory drugs may be prescribed to decrease inflammation and prevent swelling of the joint capsule. The horse may need to be rested for four to six weeks. In some cases, applying a pressure bandage is helpful.

Adding vitamins and minerals to the diet may relieve bog spavin if it is caused by a nutritional deficiency. A veterinarian's advice as to which supplements will work best for a particular horse is recommended.

If osteochondritis dissecans is a factor, surgery may be needed to correct the problem. An X-ray examination will allow the veterinarian to see the bone and any bone proliferation that is causing the arthritic condition. If serious enough, fragments should be removed by arthroscopy followed by rest, a healthy diet, and a gradual return to exercise.

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