Biceps Tendon

1. Overview

The biceps tendon refers to the fibrous connective tissue that attaches the biceps brachii muscle to bone at both the shoulder and the elbow. It consists of two proximal tendons—the long head and short head—and one distal tendon. These tendons transmit muscular force, enabling powerful flexion and supination of the forearm, and contribute to shoulder stabilization. Biceps tendon injuries are common and often involve overuse or trauma, especially in athletes and manual laborers.

2. Location

The biceps tendon is found in both the shoulder (proximal) and elbow (distal) regions:

• Long head tendon: Originates from the supraglenoid tubercle of the scapula, passes through the glenohumeral joint, and descends in the intertubercular (bicipital) groove of the humerus.

• Short head tendon: Originates from the coracoid process of the scapula.

• Distal tendon: Inserts into the radial tuberosity and gives rise to the bicipital aponeurosis, which blends into the deep fascia of the forearm.

3. Structure

The biceps tendons are composed of dense regular connective tissue rich in type I collagen, providing tensile strength and elasticity:

• Proximal tendons:

  • The long head is intracapsular but extrasynovial, encased in a synovial sheath as it runs through the shoulder joint.

  • The short head is extra-articular and more direct in its path to the coracoid process.

• Distal tendon:

  • Forms a thick, round cord inserting onto the radial tuberosity and the bicipital aponeurosis, distributing force into the forearm fascia.

• Innervation: The muscle and tendon are functionally connected via the musculocutaneous nerve (C5–C7).

4. Function

The biceps tendons play a crucial role in transferring force generated by the biceps brachii muscle:

• Forearm supination: The distal tendon enables supination of the forearm, especially when the elbow is flexed.

• Elbow flexion: Assists in lifting and bending the elbow.

• Shoulder flexion: Both proximal tendons contribute to raising the arm at the shoulder joint.

• Shoulder stabilization: The long head tendon helps stabilize the humeral head within the glenoid fossa during upper limb motion.

5. Physiological role(s)

Beyond basic movement, biceps tendons are essential for:

• Dynamic joint control: Stabilize both the glenohumeral joint (via the long head) and elbow joint during motion.

• Proprioception: Contain sensory receptors that provide information on joint position and muscular tension.

• Load distribution: The distal tendon and aponeurosis distribute muscular forces efficiently across the elbow and forearm.

6. Clinical Significance

Biceps tendon disorders are common and can significantly affect upper limb function:

• Biceps tendinitis:

  • Inflammation of the long head tendon due to overuse, impingement, or degeneration. Common in overhead athletes.

• Tendon rupture:

  • Proximal rupture: Typically involves the long head; presents as a “Popeye” deformity and may not severely affect strength.

  • Distal rupture: Less common but more functionally debilitating; significantly reduces supination strength and usually requires surgical repair.

• Tendon subluxation:

  • The long head tendon may dislocate from the bicipital groove if the transverse humeral ligament is torn, leading to shoulder pain and snapping.

• Degenerative changes:

  • Common with aging and repetitive activity; may lead to partial tears or attritional failure of the tendon.

• Surgical interventions:

  • Tenotomy: Simple release of the long head tendon; may cause cosmetic deformity but relieves pain.

  • Tenodesis: Reattachment of the tendon to the humerus to preserve contour and function; preferred in active individuals.