Biceps Tendinitis

Anatomy

The shoulder joint consists of the shallow ball-and-socket articulation of the humerus (upper arm bone) and scapula (shoulder blade). In this way, the humerus sits on the scapula like a golf ball on a tee. The scapula moves freely on the posterior chest wall and is connected to the rest of the skeleton only by the clavicle, or collarbone. These relationships allow the shoulder to have tremendous mobility but put a greater strain on the soft tissue structures (muscles, ligaments, and tendons) to maintain stability and function.

One of these soft tissue structures is the tendon of the long head of the biceps, which begins within the shoulder at a bony prominence located at the superior (top) of the glenoid (socket part of the scapula). Here at its origin, the tendon is confluent with glenoid labrum (cartilage rim that deepens the shoulder socket). From the glenoid labrum, it extends as a ropelike structure that courses along the head (ball) of the humerus, exiting the shoulder through a groove in the humerus, where it is held in place by a roof of thick connective tissue. Once outside the shoulder joint, it continues down the arm for several centimeters before it blends into the biceps muscle.

Causes

The exact cause of biceps tendinitis remains controversial. Although tendinitis implies that there is a primary inflammatory cause for this disorder, acute inflammation is not common and likely represents a small subgroup of patients with biceps tendinitis. More commonly, this diagnosis is seen in the setting of biceps tendon degenerative changes. Degenerative changes in the tendon are due to wear and tear from overuse, age, or impingement from the bony structures of the shoulder. These degenerative changes in the tendon are marked by a tendon that is softened, thickened, and frayed. Fluid, debris, and calcification can be seen around the tendon. Occasionally, the biceps tendon can be unstable in the groove of the humerus, moving up and out of its normal position, a condition called subluxation.

These degenerative changes in the biceps tendon are often seen alongside other shoulder problems, including rotator cuff tendinitis or tears, shoulder impingement, bursitis, and shoulder instability, suggesting that biceps tendinitis is the result of a more general shoulder dysfunction. This also provides the rationale for treating biceps tendinitis through general shoulder rehabilitation (Figure 1, next page).

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