Description

When the fiber-like connective tissues in the horse's legs that connect the various bones and work together as the horse moves become excessively stressed, the pulley-like bundles of fibers known as ligaments become strained and begin to break down. 

The suspensory ligament is a wide, thick, elastic, tendon-like band that begins at the back of the cannon bone and attaches to the pastern bone below. The ligament divides into two strands that surround and partially enclose the sesamoid bones.

The primary function of the suspensory ligament is to prevent excessive extension of the fetlock joint during the weight-bearing phase of the horse's stride. This suspensory apparatus acts like a spring, or a rubber band, that helps support the horse's weight while acting as shock absorbers for the legs.

Suspensory ligament strain results from excessive stress on the ligament. The extensor branches of the ligament keep the pastern joint from buckling forward. Smaller branches join the major extensor tendon of the limb.

Symptoms

• Lameness
• Thickening of the affected area of the leg
• Heat and tenderness
• Fetlock may sink towards ground if ligament is ruptured

Causes

Excessive stress placed on the suspensory ligament apparatus during a jump or at fast speeds causes the ligament to over-stretch, tearing the fibers attached to the sesamoid or cannon bones. The degree of severity depends on how destructive the damage is to the fibers that are frayed and pulled apart.

Lameness can vary from mild and transient to severe. Repeated injuries result in thickening of the tendon or ligament and persistent lameness.

Prevention

Poor hoof balance is seen by some as a predisposing factor for suspensory ligament damage because it puts more stress and strain on parts of the leg. A good farrier can make sure the hooves are balanced and trimmed properly. This, along with proper shoeing, can prevent injury.

Proper conditioning of the horse is important because exhaustion is another probable factor in suspensory ligament injuries. When a horse is tired or pushed beyond endurance, the gait is affected, especially when work requires speed. As a result, injuries are more common in horses that are tired at the end of a race or workout. .

Treatment

Treatment of suspensory damage is usually based on an ultrasound examination to determine the extent of the injury. In cases where the damage is localized to the cannon bone attachment, injection of anti-inflammatory drugs, such as corticosteroids, may be used to reduce inflammation.

Cold hosing and icing for the first week or two, along with corrective shoeing to raise the heel and decrease tension on the damaged ligament, are often recommended treatments.

Ordinarily, the horse will be taken out of hard training, but can continue exercising by walking daily. Some veterinarians recommend the use of electromagnetic machines, such as the Therascope, to treat soft-tissue injuries in the suspensory area.

For horses that do not respond to conservative treatment, shock wave therapy can be quite useful. This procedure requires that the horse be anesthetized, but since the success rate is high, it is worth considering if other treatments do not result in healing the strained ligaments.