Description

In the horse, the two digital flexor tendons run down the back of each leg, with the deep digital flexor tendon lying beneath the outer or superficial tendon. These two tendons work together to flex the knee and all the joints below the knee when the horse moves. Weakness involving the flexor tendons is usually quite apparent, since any problems with the tendons affects the foal or horse's stability and gait.

In the hind limbs, the flexors also straighten the hock. The main function of tendons is to transmit muscle power to the lower leg, and healthy tendons are able to bear extreme stretching forces. Flexor tendon laxity is very common in the newborn foal, especially if the foal is weak or premature. In older horses, the flexor tendons may become weak or lax as the horse ages.

Symptoms

• Inability to stand properly
• Sinking of the fetlocks
• Uneven gait

Causes

In newborn foals, weak flexor tendons are fairly common, especially if the foal is premature or weak. Usually, as the foal gains strength, the problem self-corrects.

In older horses, the tendons may become weakened because of previous injuries or diseases, nutritional deficiencies, lack of exercise, or normal aging.

Prevention

Proper care of the brood mare, with good nutrition and attention to help ensure the foal is not delivered prematurely, will increase the likelihood that foals will be delivered with fully-developed bone, muscular, and tendon/ligament strength.

With older horses, prompt attention to tendon injuries, good nutrition, and sufficient exercise will help prevent development of weak or lax flexor tendons.

Treatment

Treatment of weak flexor tendons in foals is necessary when the foal has difficulty standing or when the weakness does not improve or self-correct within a few days of delivery. Examination by a veterinarian and a competent farrier often results in heel extensions being applied to tip the foal forward onto the toes, while making sure to protect the heel bulbs. Exercise is usually restricted to give the tendons time to gradually gain strength and elasticity.

Tendon fibers take some time to gain strength and elasticity, and in all cases, tendon overloading should be avoided. Some veterinarians believe that specific nutrients help improve the strength and elasticity of tendons.

Daily supplementation with Vitamin A, Vitamin D, selenium, copper, zinc, and manganese is often recommended. In addition, a supplement of good quality protein, such as soybean, canola, or lupin bean meal may be recommended to supply amino acid building blocks for tendon repair and strength.