If your horse frequently suffers from lameness, he may have a case of tendinitis, an inflammation of the tendons and the tendon-muscle attachments. Tendons are composed of collagen fibers arranged to make the tendons elastic. This elasticity stores the energy that is used during the horse's stride.
When a muscle contracts, it pulls on the tendons. During exercise, tendons can normally withstand strains of 3 percent to 5 percent (similar to being able to stretch 3 percent to 5 percent of the tendon's original length). But if a horse overexerts himself and puts a strain of 8 percent to 12 percent, the collagen fibers can break. The breakage results in inflammation, swelling, pain and lameness.
The primary cause of tendinitis is overstretching, either as a single excessive loading strain (a single bad step on uneven ground) or as a repetitive strain associated with frequent overloading of the limb (such as with a galloping race horse). Tendinitis is more likely to occur if the horse's muscles are weak and fatigued during competitions, which can lead to hyperextension of the fetlock joint, and overstretching of the tendons.
Inadequate training and conditioning may also predispose a horse to tendon injury. Tendons and ligaments are known to develop strength with appropriate conditioning exercises. The injury most often occurs in the back part of the forelimbs, where the leg bends, no matter the breed or gender. However, older horses can develop tendinitis in both the front and hind legs.
What to Watch For
Recovery from tendinitis can take 6 months to more than a year, depending on the extent of damage. For this reason it is important to diagnose and treat injuries quickly before damage is extensive.
Initial therapy is directed at reducing the inflammation present in an acute injury. Rest, cold therapy (water, ice pack), bandaging, and the use of systemic anti-inflammatory medications are recommended. Cold therapy should be applied frequently throughout the day but the duration of application limited to less than 20 minutes at a time.
Stall rest is important until the horse is able to walk soundly. Once walking soundly, controlled hand-walking exercise can be started. Increase in intensity and duration of exercise will be directed by the progression of healing seen in sequential ultrasound evaluations. Tendon splitting is recommended in acute superficial digital flexor tendon lesions where the lesion is located in the center of the tendon.
There are a number of procedures available to treat tendinitis:
The injured tendon initially heals with scar tissue that is later remodeled to tendon collagen. The collagen fibers are not in their original alignment, which results in a tendon that is less elastic. Prognosis for recovery and return to use depends on the severity of the injury and the horse's occupation. Horses that are returned to less strenuous endeavors generally have a more favorable outcome.
Horses should be seen on an emergency basis if they develop acute swelling of the tendon and lameness. Early intervention can minimize progression of the lesion. It is important that owners adhere to the veterinarian's treatment plan. Failure to do so often leads to protracted healing and unsatisfactory long-term results.