Causes / typical injury mechanism: Proximal biceps tendonitis is a well-known cause of anterior shoulder pain.

The biceps brachii is separated into 2 discrete muscle bellies, the long and short heads. The tendon of the long head of the biceps brachii (LHB) is the tendon implicated in this disease process. This tendon arises from the supraglenoid tubercle within the shoulder joint, where it is intimately associated with the superior glenoid labrum. It subsequently exits the joint capsule via the biceps pulley and travels inferiorly within the bicipital groove, covered by the transverse humeral ligament.

Classic history and presentation: Proximal biceps tendonitis can occur after repetitive overhead activity or lifting of the shoulder, resulting in pain in the anterior aspect of the shoulder joint.

In younger patients and athletes who throw overhead, proximal biceps tendonitis typically presents as an isolated condition (5% of patients). In older adults, the condition is typically associated with additional shoulder pathology such as impingement and rotator cuff tears. It is present in up to 41% of patients with complete rotator cuff tears.

Prevalence: The prevalence of this condition is approximately 0.5 per 100 000, and it is most common in adults older than 50 years. Younger patients in their 20s and 30s can experience proximal biceps tendonitis with certain repetitive overhead athletic activities, such as throwing.

Sex / gender: It is 3 times more common in male patients.

Risk factors: Risk factors include congenital anomalies of the bicipital groove, aging, throwing sports (especially overhead), contact sports, volleyball, swimming, weightlifting, gymnastics, martial arts, and occupations with repetitive overhead activity (eg, carpenters, painters, electricians, etc).

Pathophysiology: The pathophysiology is more often a tendinosis rather than a true inflammatory process, tending to arise as a result of repetitive overuse / microtrauma, friction, and traction along the tendon's course. Early in the process, inflammation develops in the tendinous portion within the bicipital groove. The tendon then enlarges secondarily to swelling and/or internal hemorrhage, further irritating it and its associated sheath within the confined space of the groove. As this progresses, sheath thickening and vascular compromise ensue. This weakens the collagen fibers of the tendon and results in fibrosis and scarring, further decreasing tendon mobility and effectively anchoring it within the groove. The tendon is often surrounded by a sheath of tenosynovitis.