The glenoid labrum is a ring of fibrocartilage found within the shoulder joint, contributing significantly to the mechanical stability and function of the human shoulder. This structure acts much like a gasket, enhancing the fit between the two main bones of the joint. Its integrity is important for smooth upper body movement, particularly in activities that involve reaching overhead.
Anatomy of the Glenohumeral Joint
The glenoid labrum is part of the glenohumeral joint, the primary joint of the shoulder. This joint is a ball-and-socket mechanism, where the rounded head of the humerus (upper arm bone) rests within the shallow glenoid cavity (socket) of the shoulder blade (scapula). The labrum is a dense, rubbery tissue that forms a continuous rim around the circumference of the glenoid socket.
This fibrocartilaginous structure attaches directly to the bony edge of the glenoid cavity, creating a deeper cup for the humeral head. The labrum is generally triangular in cross-section, typically measuring around three millimeters thick and four millimeters wide.
Stabilizing the Shoulder
The glenoid labrum compensates for the natural mismatch between the large humeral head and the small glenoid socket. By encircling the socket, the labrum deepens the glenoid cavity, increasing its depth by approximately 50%. This anatomical augmentation is a static stabilizer, contributing to joint stability without requiring muscle contraction.
The labrum also stabilizes the joint by creating a suction effect within the joint capsule, which helps hold the ball and socket together. Furthermore, the labrum serves as an attachment site for the glenohumeral ligaments that surround the joint. It is also the anchor point for the tendon of the long head of the biceps muscle in the superior region of the shoulder.
Common Types of Labral Injuries
Injuries to the labrum often result from sudden trauma, such as a fall onto an outstretched arm, or from repetitive overhead motions common in sports like baseball or tennis. These mechanisms can cause the labrum to tear away from the bone, leading to pain and instability. Tears are classified based on their location around the glenoid socket.
Two common labral tears are the SLAP tear and the Bankart lesion. A SLAP tear (Superior Labrum Anterior to Posterior) involves damage to the upper portion of the labrum where the biceps tendon attaches. This injury is often seen in overhead athletes or following a traumatic compression force. The tear extends from the anterior to the posterior superior labrum.
A Bankart lesion is a tear of the anterior-inferior labrum. This lesion is the most common labral injury associated with a traumatic shoulder dislocation, where the humeral head is forced out of the socket. Because it results from the shoulder slipping out, a Bankart lesion leads to a feeling of apprehension or instability in the joint.
Options for Repair and Recovery
The treatment path for a labral tear depends on the tear’s type, size, and the patient’s activity level. For less severe tears, or in individuals who do not participate in demanding physical activities, non-surgical management is typically used first. This conservative approach involves rest, anti-inflammatory medications to manage pain and swelling, and physical therapy.
Physical therapy focuses on strengthening the rotator cuff and the muscles surrounding the shoulder blade, which helps stabilize the joint and reduce stress on the damaged labrum. If non-surgical treatment fails, or for significant tears causing instability, an arthroscopic repair may be necessary. This minimally invasive surgery involves reattaching the torn labrum to the glenoid bone using small sutures and anchors.
Following surgical repair, recovery begins with immobilization in a sling, usually lasting a few weeks, to protect the repair. This is followed by rehabilitation to restore full range of motion and strength. While gentle exercises start early, athletes can expect a gradual return to sports-specific activities, with full recovery often taking up to six months.