Causes / typical injury mechanism: The distal biceps tendon is very different from the proximal, long-head biceps tendon. The biceps muscle has 2 proximal origins: the superior glenoid within the shoulder joint (long head) and coracoid process (short head). It has 1 distal insertion: the radial tuberosity near the elbow. The long-head tendon is associated with the shoulder. See proximal biceps tendonitis for more information.

Distal biceps tendinopathy (DBT) affects the insertion of the biceps muscle. It is usually associated with repetitive, forceful contractions of the biceps muscle against resistance, resulting in microtears and inflammation of the tendon's insertion just distal to the elbow joint. The weakened tendon can rupture acutely if an uncontrolled load is applied.

Tendinopathy includes tendonitis (acute inflammation of the tendon) and tendinosis (chronic degeneration with abnormal healing and less inflammation; healthy tendon is replaced by fibrous scar tissue). These conditions are closely related and grouped together as tendinopathy.

Classic history and presentation: This overuse injury is most commonly seen in individuals who have repeatedly loaded the biceps muscle. Patients present with pain localized to the antecubital space and volar proximal forearm with weakened elbow flexion and forearm supination. Pain is worse with activity (such as heavy lifting and using a screwdriver) and improves with rest.

Prevalence:

• Age – Patients are primarily between 30 and 60 years of age.
• Sex / gender – Males are more commonly affected.

Risk factors:

• Smoking
• Elevated body mass index (BMI)
• Male sex
• Regular manual labor
• Anabolic steroid use

Pathophysiology: DBT is caused by structural changes that occur in response to repetitive, resisted loading of the tendon. The mechanism is not well understood. Increased vascularization of the stressed tendon is an early change, which is later accompanied by thickening.

The pronated forearm provides about 50% less space for the biceps tendon compared to the supinated forearm. Therefore, there may be some impingement of the tendon causing gradual degeneration.

Grade / classification system: No generally accepted classification system is used for DBT. The disorder ranges from bicipitoradial bursitis through chronic degeneration, and from partial tear to complete rupture of the distal biceps tendon. Symptoms are categorized as acute (developed less than 4 weeks ago) or chronic (lasting for more than 4 weeks).

Related topic: distal biceps tendon rupture