The supraspinatus tendon is a small, but frequently injured, structure located within the shoulder. It is a key component of the shoulder’s mechanics, connecting the supraspinatus muscle to the upper arm bone. Because it operates in a narrow space and is repeatedly stressed during arm movement, it is a common source of shoulder pain and limited function.
Pinpointing the Supraspinatus Tendon
The supraspinatus muscle is nestled in the supraspinous fossa, a concave area of the shoulder blade just above the prominent spine of the scapula. The muscle fibers converge into the tendon as they travel outward toward the upper arm bone. The tendon passes through a tight passageway beneath the acromion, a bony arch that is the highest point of the shoulder.
The tendon attaches to the superior facet of the greater tubercle, a bump on the top of the humerus (upper arm bone). This insertion point allows the muscle to exert force on the arm. The supraspinatus is one of the four tendons that form the rotator cuff, a complex of tissues that cups and stabilizes the shoulder joint. This arrangement makes the tendon highly susceptible to friction and pressure, especially when the arm is lifted.
The Crucial Role of the Supraspinatus
The primary function of the supraspinatus is to initiate arm lifting away from the body, a motion called abduction. It is responsible for the first 10 to 20 degrees of this movement before the larger deltoid muscle completes the lift. Without a healthy supraspinatus, the initial phase of arm elevation is difficult or impossible to perform smoothly.
The muscle and its tendon also provide dynamic stabilization of the glenohumeral joint. As the arm moves, the supraspinatus coordinates with the other rotator cuff muscles to keep the head of the humerus centered within the shoulder socket. This action prevents the arm bone from migrating upward, which causes painful pinching against the overlying bone.
Understanding Supraspinatus Injuries
Injuries to the supraspinatus tendon generally fall into two main categories: tendinitis and tears. Tendinitis describes inflammation or irritation, often caused by repetitive overhead motions or prolonged impingement. Tears involve a structural disruption of the tendon fibers. These can be partial-thickness (frayed but not completely separated) or full-thickness (severed entirely from the bone attachment).
Acute tears result from a sudden, traumatic event, such as falling onto an outstretched arm or lifting a very heavy object with a jerking motion. Degenerative tears are common in people over 40. They develop slowly due to age-related wear and tear, reduced blood supply, and chronic friction from conditions like shoulder impingement. Repetitive activities in sports or certain occupations, such as painting or swimming, accelerate this degenerative process.
The characteristic pain includes discomfort felt at the top and side of the shoulder, which may radiate down the arm. Weakness, particularly when attempting to lift the arm or carry objects, is a significant symptom. Pain that interrupts sleep, especially when lying on the affected side, is also common. An acute tear may cause immediate, intense pain and a distinct popping sensation, followed by an immediate loss of strength.
For initial self-management of acute pain or inflammation, the RICE protocol (Rest, Ice, Compression, and Elevation) is often recommended. Rest involves avoiding painful activities and may require a temporary sling. Applying a cold pack wrapped in a towel to the area for 15 to 20 minutes several times a day helps reduce pain and swelling. Focusing on rest and icing is the primary non-medical action.
Seek professional medical attention if the pain is severe, if there is a sudden loss of function after an incident, or if pain persists for more than a week despite initial rest and ice. Chronic pain that does not improve with activity modification also warrants a visit to prevent the injury from worsening or leading to long-term complications. Ignoring symptoms can cause a tear to enlarge or result in muscle atrophy, making recovery more challenging.