Supraspinatus

The supraspinatus is a relatively small muscle located deep to the trapezius and deltoid on the shoulder. The muscle belly is located in the supraspinous fossa, just superior to the spine of the scapula. The muscle runs horizontally from the superior angle of the scapula laterally to the acromion process. Here, the tendon drops deep to the acromion process, crosses the glenohumeral joint superiorly, then descends and inserts on the greater tubercle of the humerus.

The supraspinatus is one of four muscles of the shoulder that make up the rotator cuff. The supraspinatus, infraspinatus, teres minor, and subscapularis muscles surround and function as a unit to stabilize the humeral head in the glenoid fossa. Each muscle has a specific role in positioning and steering the head of the humerus as the arm moves into different positions. Without the rotator cuff dynamically stabilizing this highly mobile, ball-and-socket joint, the humeral head would collide with surrounding bony structures such as the acromion process superiorly or coracoid process anteriorly and medially. This may result in compression of adjacent soft tissues and associated damage to bursae, tendons, nerves, and blood vessels critical to the health and function of the upper extremity.

Specifically, the supraspinatus maneuvers the humeral head inferiorly as prime mover muscles such as the deltoid move the shoulder through abduction. When the supraspinatus contracts, it levers the proximal end of the humerus downward as the distal end rises upward. Ideally, this occurs in tandem with activation of the deltoid muscle during shoulder abduction. Subtle depression of the humeral head during shoulder abduction positions the humeral head centrally within the glenoid fossa, preventing contact or impingement on the acromion process. By maintaining adequate space and optimal mechanics throughout the full range of shoulder abduction, the supraspinatus prevents compression and excessive friction that is damaging to surrounding soft tissues.

The location of the supraspinatus tendon deep to the acromion process makes this structure particularly vulnerable to tendinitis, impingement, and tearing. Excessive friction and trauma to this muscle is common and debilitating to the function of the entire shoulder. Additionally, bony anomalies such as an excessively angled or "hooked" acromion, and postural deviations such as a forward head or rounded shoulders, can inhibit activation of the rotator cuff and encourage shoulder impingement syndromes.

Establishing and maintaining proper posture and a strong, healthy supraspinatus in conjunction with the other rotator cuff muscles is essential to optimal shoulder function.

Palpating Supraspinatus

Positioning: client prone with arm at side.

1. Palpate the spine of the scapula with your thumb.
2. Move your thumb superiorly above the spine to locate the supraspinous fossa.
3. Locate the muscle belly in the supraspinous fossa.
4. Follow the muscle belly to the acromion process, then locate the tendon laterally between the lateral acromion and greater tubercle of the humerus.
5. Resist as the client initiates shoulder abduction to ensure proper location.

Client Homework: Shoulder Depression Stretch

1. Stand or sit up straight with the head facing forward.
2. Keep your neck elongated and your back straight as you reach back and clasp your hands behind your back, palms together. Grasp a towel if you are unable to clasp your hands.
3. Gently squeeze your shoulder blades together and straighten your arms.
4. Take several deep breaths and push your shoulders down as you exhale.
5. Maintaining a long neck and straight back, slowly rotate your head from side to side.