What are the different types of supraspinatus injury?

A supraspinatus injury describes any damage to the supraspinatus muscle, the most frequently injured of the four rotator cuff muscles. The supraspinatus is the most superior of these muscles and supports the joint from its position at the top of the shoulder. All four muscles are responsible for stabilizing the glenohumeral or shoulder joint, supporting it through 360 degrees of movement and maintaining the position of the head of the humerus bone in the glenoid fossa of the scapula. Additionally, the supraspinatus initiates the abduction of the arm or lifts it away from the body to the side. Common types of supraspinatus injury include tendonitis of its attachment tendon in the shoulder, muscle tears, and impingement of the tendon against the acromion process of the scapula.

This muscle originates from the supraspinatus fossa, a cavity in the upper part of the posterior surface of the scapula on the side closest to the spine. Exiting almost horizontally from the fossa, the supraspinatus converges to form a tendon that passes just anterior and slightly superior to the acromion of the scapula. A bony club-shaped prominence arising from the scapular crest on the posterior surface of the scapula, the acromion can be felt at the peak of the shoulder where the clavicle meets the scapula. The supraspinatus tendon, after passing just in front of the acromion, inserts on top of the humerus bone just before the glenohumeral joint at the greater tubercle.

The location of this tendon adjacent to the acromion leaves it susceptible to a condition known as impingement syndrome. Impingement occurs when the space through which the tendon passes narrows, putting pressure and friction on the tissue. Supraspinatus impingement is a common type of supraspinatus injury, as muscle imbalances in many people, particularly weightlifters and athletes, cause the shoulders to roll forward and internally rotate. This postural imbalance reduces the space between the acromion and the humerus and pinches the supraspinatus tendon, an imbalance that can be treated with corrective exercise. Similarly, growths on the acromion like bone spurs can lead to supraspinatus impingement, which presents with pain, shoulder weakness, and restricted range of motion in the shoulder joint.

Supraspinatus impingement is often accompanied by tendinitis, a type of supraspinatus injury in which the tendon becomes inflamed and irritated as it rubs against adjacent bone. Tendinitis is usually caused by frequent and repetitive movements, and supraspinatus tendinitis is often seen in athletes whose sports require an overhead throwing motion, such as baseball pitchers. This injury is accompanied by pain, stiffness, tenderness, and limited range of motion in the affected joint, and is usually treated with ice, anti-inflammatory pain medications, and avoiding the movement patterns that caused it.

A third category of supraspinatus injury is a muscle tear. Although blunt trauma can cause this injury, it is more likely to be caused by the same repetitive motions that weakened the tendon and led to tendinitis. In other words, an untreated case of supraspinatus tendonitis can lead to further rupture of the tendon resulting in a tear.

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