What are Chronic Proliferative Synovitis?
Proliferative synovitis occurs when the pad made of cartilage with a great number of fibers, located on the dorsoproximal aspect of the joint capsule attachment of the fetlock joint (metacarpophalangeal and metatarsophalangeal joints) becomes swollen. It is believed that the swelling is due to repetitive trauma as a result of exercise. This condition is most likely to occur in race horses but can be found in non-racing breeds. Early diagnosis is important in order to avoid additional issues as a result of the synovitis.
Most likely to occur in race horses, chronic proliferative synovitis occurs when the fibrocartilaginous pad of the fetlock joint becomes swollen, likely as a result of repetitive trauma.
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Symptoms of Chronic Proliferative Synovitis in Horses
Should your horse be experiencing chronic proliferative synovitis, you may observe the following symptoms:
- Swelling at the front of the fetlock joint
- A reduction in your horse’s range of motion
- Pain when bending of the fetlock joint
- Some degree of lameness, which increases after bending of the fetlock joint
Should the chronic proliferative synovitis your horse is experiencing be secondary to bone or cartilage fragments or fracture, masses are typically easy to remove and your horse is expected to recover well.
In cases where the synovitis is secondary to osteoarthritis, typically the masses seen will be great in size and the condition will be more chronic. Surgery may not be a good option in these situations and the prognosis is poor.
Your horse’s osteoarthritis can be better understood by the veterinarian by looking at a radiograph at joint space or reviewing the thickness of the joint’s cartilage on an ultrasound.
Causes of Chronic Proliferative Synovitis in Horses
Chronic proliferative synovitis appears to be caused by repeated trauma to the front of your horse’s fetlock joint. Significant extension of the joint will lead to both swelling and scarring of the synovial pad. The connective tissue will thicken and in severe cases it will be prominent when viewing the joint in profile. As a result of the constant swelling, related cartilage and the hard outer layer of bone below will gradually wear away.
Diagnosis of Chronic Proliferative Synovitis in Horses
Should you notice that your horse is experiencing discomfort along the front of his fetlock joint and some degree of reduction in his range of motion, you will want to contact your veterinarian. Upon conducting a physical examination your veterinarian will examine your horse’s leg with his hands. Based on what he feels along the fetlock joint he may suspect that your horse is suffering from chronic proliferative synovitis. To confirm diagnosis as well as to determine if there are any issues with associated bone, your veterinarian may use radiography and ultrasound.
The radiograph may show a depression in the distal dorsal metacarpus, and the synovial tissue that is next to the proximal dorsal attachment of the joint capsule may be larger than usual. Should the synovial pad be greater than 4 mm thick, contain rounded distal margins or if regions in the pad are found to echo stronger than usual in the ultrasound, the pad will be considered atypical.
Treatment of Chronic Proliferative Synovitis in Horses
If your horse has been diagnosed with chronic proliferative synovitis, your veterinarian will likely recommend arthroscopic surgery in order to remove the abnormal synovial pad. After completion of surgery, medication will be administered directly into your horse’s joint. The outcome is usually good if the condition is caught early; horses are often able to return to function about six to eight weeks after their surgery and continue training around three months after surgery was performed.
Recovery of Chronic Proliferative Synovitis in Horses
Should your horse experience chronic proliferative synovitis, it is important that you work closely with your veterinarian to ensure the best possible outcome for him. If surgery is recommended, your veterinarian will discuss with you how to best aid in his recovery process. Regular follow up appointments will be necessary to assess your horse’s progress and for your veterinarian to determine when your horse can return to his regular activity.