Overview

The biceps has two separate upper attachments — the long head and the short head — but lower down the two muscle bellies join and funnel into a single shared common tendon. This tendon is the final common pathway that delivers the pull of the whole biceps to the bones it moves, so problems here can affect lifting, carrying and turning the palm upward even when the muscle itself feels normal.

Location

Formed where the long head and short head muscle bellies converge in the lower arm
Runs down the front of the arm toward the elbow
Anchors onto the forearm bone and sends a broad sheet of fibres into the deep forearm tissues

Origin, Insertion, Nerve Supply, and Action

Origin: Convergence of the long head and short head bellies of biceps brachii
Insertion: Radial tuberosity of the radius, plus the bicipital aponeurosis (lacertus fibrosus) into the deep fascia of the forearm
Nerve supply: Musculocutaneous nerve (spinal nerve roots C5–C6), which supplies the biceps it serves
Action: Transmits the biceps' pull to flex the elbow and supinate the forearm (turn the palm up)

In plain English: this is the shared "rope" the whole biceps pulls on. When it is irritated, lifting and twisting-the-palm-up movements tend to hurt at the front of the arm.

Function

Transmits the combined pull of both biceps heads to the forearm
Drives flexion of the elbow
Drives supination of the forearm
Spreads load into the forearm fascia through the bicipital aponeurosis

Structures It Connects To

Long head of biceps brachii — one of the two bellies feeding into the tendon
Short head of biceps brachii — the other belly feeding into the tendon
Radius (forearm bone) — its main bony anchor at the radial tuberosity

Movements It Assists

Elbow flexion
Forearm supination

Common Injuries

Biceps tendinopathy — irritation of the tendon with repetitive lifting or overhead loading
Distal biceps tendinopathy — irritation at the radial tuberosity attachment near the elbow
Biceps tendon instability — the tendon slipping from its normal position, causing anterior pain

Pain Referral Patterns

Pain at the front of the shoulder or upper arm that worsens with lifting and carrying
Pain when turning the palm upward against resistance
Tenderness following the line of the tendon down the front of the arm

Clinical Relevance

Because the common tendon is the final common pathway for everything the biceps does, front-of-arm pain with lifting and supination often traces to the tendon rather than the muscle belly. A sudden pop with a change in the shape of the biceps can indicate a tendon rupture and warrants prompt assessment.

Interesting Facts

The bicipital aponeurosis (lacertus fibrosus) that spreads from this tendon helps protect the artery and nerve that run just beneath it at the elbow crease — historically useful during blood draws.

Long head of biceps brachii — one of the two heads that feed this tendon
Glenohumeral joint — the shoulder joint the biceps crosses
Humerus (proximal) — the upper arm bone the biceps overlies

References

Tiwana MS, Charlick M, Varacallo M. "Anatomy, Shoulder and Upper Limb, Biceps Muscle." StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK519538/
Physiopedia. "Biceps Brachii." https://www.physio-pedia.com/Biceps_Brachii
Terminologia Anatomica (FIPAT). https://fipat.library.dal.ca/

Biceps Tendon (Common)