Infraspinatus tendon contracture is the result of damage to the infraspinatus muscle and its tendon. The infraspinatus tendon helps support the shoulder joint, and allows for flexion and external rotation of the shoulder. As the damaged muscle and tendon heal, the normal tissue is replaced by fibrous scar tissue. Eventually the muscle loses its normal function, and the presence of scar tissue limits the ability of the shoulder joint to move through its full range of motion. (diagram of normal anatomy)
Infraspinatus tendon contracture occurs most commonly in active medium to large breed adult dogs. It is often an injury sustained by sporting and hunting dogs, such as Labrador Retrievers.
Initially, there is a sudden onset of lameness as a result of trauma or during exercise. The lameness and pain associated with the injury usually subsides in 10-14 days. As the muscle heals, the damaged muscle fibers are replaced with scar tissue. The muscle becomes gradually more and more nonfunctional, and a gait abnormality appears 3-4 weeks after the original injury. The animal will be unable to rotate the shoulder internally, but shows no signs of pain. When the dog walks, it will circumduct the leg, meaning it rotates outward. Because scar tissue is not stretchy like muscle, it tightens as it develops. Therefore, the contracted tendon causes the dog to have a characteristic stance, in which the elbow and foot are adducted, meaning held away from the body. As a result of the shortened muscle and tendon, the dog’s affected leg is slightly shorter than the normal leg, and he/she cannot fully extend the shoulder. Because the muscle is no longer functional, it undergoes atrophy, and the scapula becomes more prominent, which is apparent on palpation during a physical exam. Although lameness is consistently present in dogs with infraspinatus tendon contracture, it is important to note that once the initial injury heals, the contracture is not painful. (picture of dog’s stance with contracted infraspinatus m.)
Your veterinarian can diagnose a contracted infraspinatus tendon based on the dog’s history, physical exam, and clinical signs. Radiographs are usually normal. A suspected infraspinatus contracture can be
confirmed using ultrasound.
A contracted infraspinatus tendon can be the result of direct trauma to the area, but is more commonly associated with indirect trauma, such as in cases of overuse, or any other event that leads to incomplete rupture of the tendon.
There is no medical management for infraspinatus tendon contracture, the only treatment is surgery. An incision is made over the shoulder region and the contracted tendon is severed as it crosses over the shoulder joint, a procedure called a tenotomy.
Dogs that participate in strenuous activity, such as working, hunting, or agility dogs should be properly conditioned and “warmed up” prior to exercise. If your dog sustains an injury during exercise, it is important to seek veterinary treatment immediately. Physical therapy and anti-inflammatories can help limit the damage caused by inflammation and prevent the formation of scar tissue. Because the initial period of lameness subsides, contracture has already occurred by the time most of these patients are seen by their veterinarian.
Without surgery, the condition will not resolve. However, after undergoing a tenotomy, your pet will regain normal range of motion of the shoulder joint and the abnormal gait will resolve immediately upon release of the contracted tendon. Following treatment, the patient is usually fully cured of this condition, and can return to normal activities after about two months.