Biceps Brachii: Anatomy, Function, and Clinical Relevance

The biceps brachii is a two-headed muscle on the anterior upper arm.

Anatomy

• Long head: Origin – supraglenoid tubercle of scapula (intra-articular tendon).
• Short head: Origin – coracoid process of scapula.
• Insertion: Radial tuberosity (via biceps tendon) and bicipital aponeurosis (lacertus fibrosus) to deep forearm fascia.

Actions

1. Supination: Primary supinator (most powerful with elbow flexed).
2. Elbow Flexion: Strong flexor (especially supinated).
3. Weak Shoulder Flexion: Long head assists.

Clinical Correlates

• Rupture: Usually long head at proximal tendon ("Popeye sign" – distal migration of belly). Distal rupture rare (forced extension against resistance).
• Tendinopathy: Long head in bicipital groove (impingement, SLAP lesions).
• Innervation: Musculocutaneous nerve (C5–C6).
• Testing: Resisted supination + flexion; palpate tendon in groove.