Description

A tendon is a fibrous "rope" that transfers the force exerted by a muscle from the muscle to the part of the body which is to be moved. When horse's tendons are mentioned, it nearly always means the tendons that run down the lower half of the leg and that are responsible for moving the foot.

The tendons known as flexor tendons run down the back of the leg and come under terrific strain because the leg is bearing weight and moving when they are in use. Each tendon is made up of spindle-shaped bundles of collagen fibers with a small amount of elasticity.

In a galloping horse, a great deal of weight is being supported by the very small cross sectional area of the flexor tendons, making the flexor tendon vulnerable to injury. When the tendon fibers tear, bleeding causes acute swelling, heat and pain.

Bowed tendon injuries follow excessive strain of the superficial digital flexor tendon in the middle of the cannon bone region which extends from beneath the structures of the knee to the fetlock joint below. The injury can be performance limiting and can result in the end of the horse's career. The damage may occur from a single incident or may develop over a period of time.

The injury usually occurs at the smallest cross-sectional diameter of tendon fibers in the mid-cannon bone region. Although palpation may help with the assessment of the damage, ultrasonography by a veterinarian is the best insurance against further injury to the tendon.

Once the natural arrangement of the tendon fibers is disrupted, inflammation, edema and hemorrhage further damage the fiber bundles. At this point, some horses will become lame, but others will show tendon swelling without signs of lameness.

It is important to understand that considerable damage can be present within the tendon even though external palpation may find only slight swelling.

Symptoms

• Swelling that resembles an archer's bow
• Inflammation
• Pain
• Lameness
• Favoring of one leg

Causes

The tendon is injured when the horse puts more force onto its leg than the tendon can bear. This may be due to accidentally positioning the leg improperly with respect to the horse's movement, or it may be due to improper shoeing.

Many people tend to believe that bowed tendon injuries happen only to race horses, but these injuries can happen to any breed or type of horse performing almost any activity.

Horses may or may not be lame. Since tendon damage is very difficult to diagnose, a veterinarian should be called for an ultrasonographic evaluation of the swelling.

Prevention

Keeping the horse in good physical condition, making sure that shoes fit properly and that hooves are trimmed appropriately and kept in good condition, plus a program of appropriate exercise will help prevent problems such as bowed tendons.

In the case of bowed tendons, the cliche: "An ounce of prevention is worth a pound of cure" holds true. Many tendon injuries, including bowed tendons, can be prevented by making sure that horses are well conditioned and shoed properly before engaging in challenging exercise or work.

Treatment

Ultrasound examinations are necessary both for initial diagnosis to determine the amount of damage and for monitoring treatment during the healing process.

The first treatment for a strained or bowed tendon is rest. Rest prevents further damage and allows healing to take place. The horse should be confined in a stall with one or two short periods of walking with the handler each day.

This exercise ensures that gentle tension is placed on the new collagen fibers being formed resulting in a stronger repair. A veterinarian can best determine the length of time needed for the tendons to heal.

A second basic treatment is the application of cold compresses. The cold causes the contraction of the blood vessels in the inflamed area so less tissue fluid accumulates. Pressure from fluid buildup is the major cause of pain and fluids can clot and form adhesions which can affect future movement.

The third method of treatment is the providing of support for the affected leg. Bandaging that is firm, but not tight, will help limit further swelling and provide support to the damaged tendon,

The final basic treatment is the use of drugs to remove the edema and reduce inflammation. If the injury is caught early and treated by a veterinarian, the worst problems with swelling and inflammation can be prevented. Diuretics and anti-inflammatory drugs, as well as pain killers, may be very helpful in preventing further damage and encouraging the healing process.

In addition to these basic treatments surgical treatments are sometime recommended by veterinarians. Other treatments such as therapeutic ultrasound, low power laser treatments, acupuncture, hydrotherapy and electromagnets are also thought to promote tendon healing in some cases. A veterinarian can help choose the best treatment for each individual horse.

Once healing is well on its way, a gradual return to activity following the advice of a veterinarian is important. Tendon rehabilitation is a slow process that can be frustrating if the horse suffers setbacks due to re-injury. Monitoring the horses progress with periodic ultrasound examinations can eliminate these setbacks.