The greater tuberosity is a prominent bony feature located near the shoulder joint at the top of the upper arm bone, the humerus. This raised area functions as a critical attachment site for several large tendons that control shoulder motion. Its location makes it a focal point for the biomechanics of the shoulder, influencing arm movements and complex athletic maneuvers. The structure is frequently involved in common shoulder injuries, giving it significant clinical relevance in orthopedic medicine.
Anatomical Location and Structure
The greater tuberosity is situated on the lateral, or outer, side of the proximal humerus, the rounded top section of the upper arm bone closest to the shoulder. It is one of two bony prominences on the humerus head; the smaller lesser tuberosity is located more medially. A deep groove, called the intertubercular sulcus or bicipital groove, separates the two tuberosities.
The tuberosity features three distinct flattened impressions, or facets, on its posterosuperior aspect. These facets are organized into superior, middle, and inferior sections, each designed to receive the tendon of a specific muscle. This organization allows for the precise transfer of force from the muscles to the humerus, necessary for controlled movement of the arm.
Functional Role in Shoulder Movement
The greater tuberosity functions primarily as the insertion point for three of the four muscles that make up the rotator cuff, a group of muscles and tendons responsible for stabilizing and moving the shoulder joint. The supraspinatus tendon attaches to the superior facet, the infraspinatus tendon inserts onto the middle facet, and the teres minor tendon attaches to the inferior facet.
These muscular attachments are essential for the shoulder’s ability to move through a wide range of motion. The supraspinatus muscle, for example, is primarily involved in initiating the abduction of the arm, which is the act of lifting the arm away from the body. Both the infraspinatus and teres minor muscles contribute significantly to the external rotation of the arm. Together, the muscles inserting on the greater tuberosity are instrumental in stabilizing the head of the humerus within the shoulder socket during dynamic movement.
Common Injuries Involving the Greater Tuberosity
Due to the high forces transmitted through its attached tendons, the greater tuberosity is prone to two main types of injuries: rotator cuff tears and fractures. Tears often occur at the site where the tendons transition into the bone, known as the footprint. The supraspinatus tendon is the most frequently injured, often tearing near its superior facet insertion point.
Greater tuberosity fractures commonly result from a traumatic event, such as a fall directly onto the shoulder or a shoulder dislocation. An avulsion fracture occurs when the force of the attached rotator cuff muscle pulling suddenly on the bone causes a fragment of the tuberosity to tear away. If the fracture is displaced, the bony fragment has moved significantly from its normal position and is often pulled superiorly and posteriorly by the contracting rotator cuff tendons. Fractures in this area interfere with the function of the stabilizing rotator cuff muscles.
Diagnosis and Initial Management
Diagnosing an injury to the greater tuberosity begins with a thorough physical examination to assess pain, swelling, and the patient’s ability to move the arm. Imaging studies are routinely used to confirm the diagnosis and determine the extent of the damage. X-rays are the initial imaging method, used to visualize the bone and determine if a fracture is present.
For a suspected rotator cuff tear or a fracture not clearly seen on an X-ray, advanced imaging like Magnetic Resonance Imaging (MRI) or ultrasound is necessary to assess the soft tissues. Initial management for most acute injuries involves immobilization of the shoulder, typically with a sling, for rest and pain control. Non-surgical treatment is recommended for minimally displaced fractures, using immobilization followed by physical therapy to restore range of motion and strength. Surgery is indicated when a fracture fragment is displaced by 5 millimeters or more, or for large, full-thickness rotator cuff tears, to reattach the bone or tendon.