Tendonitis in horses: Causes and treatment

Tendonitis is common in horses that have to gallop frequently, and causes swelling and pain.

tendonitis in horses
The swelling over the tendon sheath at the back of this horse’s leg is most likely due to tendonitis.
Photo: Dr Mac

Tendonitis in horses is more common than one may expect, and requires quick treatment. As its name indicates, tendonitis is an injury to the tendons. On the forelegs, this injury normally occurs to the superficial flexor tendon and the resulting condition is known as ‘bowed tendon’. On the hind legs, the deep flexor tendon is more commonly injured. Flexor tendons are long strips of fibrous tissue enclosed in a tendon sheath that run down the back of each leg.

Their main function is to flex the joints during movement. Horses with long pasterns and flat hooves are more likely to get tendonitis, as this conformation tends to overstretch the tendons. Rapid or uneven movement, such as galloping and turning at speed, can tear the fibres inside the tendon sheath, causing inflammation, swelling and pain. The swelling can bring about further damage to the collagen fibres of the tendon by preventing blood circulation to the area.

Symptoms of tendonitis in horses

Tendonitis in the front legs produces swelling at the back of the leg between the knee and fetlock joint. Although painful in the beginning, the lameness can decrease with time. In the hind legs, where the deep flexor tendon is affected, the horse begins to take more weight on its fore limbs, making lameness difficult to diagnose. If you run your fingers down the sides of the tendon, however, the horse will often flinch away as you reach the annular ligament, a band of fibrous tissue around the tendon midway down the shannon bone.

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Treatment

The leg should be hosed down and cold compresses applied to reduce the inflammation and swelling as soon as possible. Liniment can be rubbed in gently and a supportive bandage applied. Do not wind the bandage too tightly, as this can further damage the ligament. Generally, cotton-wool is first rolled around the leg from the knee to the hoof. Then a cotton bandage is wound evenly over the cotton wool to stabilise it and a final layer of elastic bandage or ‘Vetwrap’ is wound evenly around the leg.

The tendons can take up to six months to heal. Stall rest is important and hand walking is usually the only form of exercise allowed for four to six weeks. In the case of a superficial flexor tendon injury, diagnosis can be confirmed, and healing monitored, with ultrasound. This method is less successful with deep flexor tendonitis. Although about 80% of horses go back to work and can even do showjumping, complete cure is unlikely.

A racehorse that has a bowed tendon is never allowed to race again, as the tendon could snap during fast work such as galloping. It is important that a horse with tendonitis is always worked in tendon boots or exercise bandages after recovery, so that the tendon is properly supported. It should even be bandaged when in the stable at night, as the tendon could be re-injured if the horse slips when lying down or getting up.

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