The shoulder is supported by a set of tendons and ligaments. Tendons attach a muscle to the bone, whereas a ligament attaches one bone to another. The infraspinatus muscle is responsible for external rotation and extension of the shoulder joint.
Injury to the infraspinatus muscle usually takes place during hunting or other athletic activities. Initially, this will cause lameness, but subsequently as the muscle heals with scar tissue the muscle becomes very tight (contracture) and the limb becomes externally rotated.
Signs and diagnosis
The most common sign of an infraspinatus muscle contracture is external rotation of the limb. When walking or trotting a swinging or circumducting movement of the affected limb is seen. On physical examination, the limb cannot be internally rotated at the shoulder due to the frozen muscle. X-rays of the shoulder may be recommended to rule out other problems of the shoulder. Blood testing is performed prior to surgery to ensure a safe anesthesia.
An incision is made over the side of the affected shoulder. The tendon of the contracted infraspinatus muscle is isolated and a section of the tendon is removed to free up the movement of the shoulder.
Dogs that receive surgery are usually able to resume working activities, such as hunting, after complete healing has taken place (about four months later).
For more information on this subject, speak to the veterinarian who is treating your pet.