The supraspinatus tendon is the muscle that runs laterally across the top of the shoulder and connects the shoulder blade, or scapula, to the upper arm, or humerus. It is one of the four muscles of the rotator cuff, and its purpose is to raise the arm at the shoulder. The other three rotator cuff muscles allow rotation of the shoulder in any direction and provide shoulder stability. The supraspinatus tendon is susceptible to inflammation, tears and strains. Most common in athletes who play sports involving throwing movements, such as tennis and football, these injuries can occur in anyone of any age.
All the tendons that make up the rotator cuff surround, enclose and protect the shoulder from gravitational forces from the weight of the arm. The supraspinatus tendon in particular, which is about the width of a thumb, helps to stabilize the head of the humerus against the socket of the scapula and creates a snug ball-and-socket fit. This tendon enables the muscle to abduct the upper arm, or move it laterally away from the body allowing the arm to flap like a bird in flight.
The supraspinatus tendon is particularly vulnerable to tendinitis, which is inflammation of the tendon, as well as tendinosus, or breakdown of the tendon. When the supraspinatus tendon is overworked from strenuous activity such as carrying heavy loads, pain may be felt in the middle back of the shoulder. The pain can also run down to the forearm and be mistaken for tennis elbow.
Another condition common to the supraspinatus tendon is called impingement syndrome. This can occur if the acromion bone along the top of the shoulder pinches the tendon when the arm is raised forward or upward. Repeated pinching can eventually weaken the function of the tendon and cause it to break down. In most cases, this condition requires surgical treatment.
Tendinitis in the supraspinatus tendon can also result from sleeping on the shoulder, causing pinching in the rotator cuff. This often can cause pain when reaching for something above shoulder level. Physical therapy exercises to strengthen and tone the muscles can usually resolve the pain. If pain persists, poor blood supply may be to blame for a more chronic condition. In these more severe cases, doctors may opt for prolotherapy treatment, an injection therapy that produces new collagen that tightens the tendon and makes it stronger.