Overview

The short head is one of the two muscle bellies that together form the familiar bulge of the biceps at the front of the upper arm. Unlike the long head, whose tendon passes through the shoulder joint, the short head has a simpler, more stable start — it attaches to a bony hook on the front of the shoulder blade — so it is far less prone to joint-related irritation and is usually only involved in ordinary muscle strains.

Location

Begins at the tip of the coracoid process, a finger-like hook at the front of the scapula
Runs down the front of the upper arm, on the inner side of the long head
Merges with the long head into the common biceps tendon toward the elbow

Origin, Insertion, Nerve Supply, and Action

Origin: Apex of the coracoid process of the scapula, as a conjoint tendon shared with coracobrachialis
Insertion: Radial tuberosity of the radius via the common biceps tendon, plus the bicipital aponeurosis into the forearm fascia
Nerve supply: Musculocutaneous nerve (spinal nerve roots C5–C6)
Action: Elbow flexion and forearm supination; assists flexion and adduction of the arm at the shoulder

In plain English: the short head is the inner half of your biceps. It bends the elbow and turns the palm up, and because it starts outside the joint it rarely causes the deep shoulder pain the long head can.

Function

Flexes the elbow together with the long head
Supinates the forearm, turning the palm upward
Assists flexion and adduction of the arm at the shoulder
Adds to the front-of-arm bulk that stabilises loads carried in front of the body

Structures It Connects To

Coracoid process of the scapula — its origin, shared with coracobrachialis
Long head of biceps brachii — the neighbouring belly it merges with
Radius (forearm bone) — its bony anchor via the common tendon

Movements It Assists

Elbow flexion
Forearm supination
Shoulder flexion (assisting)

Common Injuries

Short head of biceps strain — an overload or overuse injury of the muscle belly
Overuse soreness of the biceps with repeated lifting
Biceps tendinopathy — more often involves the long head, but the short head shares the common tendon

Pain Referral Patterns

Aching or soreness along the front of the upper arm, especially after repeated lifting
Pain near the front of the shoulder over the coracoid tip with resisted elbow bending
Tightness or cramping of the front-of-arm muscle with heavy carrying

Clinical Relevance

Because its upper attachment sits outside the shoulder joint, the short head is much less involved in the joint-related biceps problems that trouble the long head. It is most often a straightforward muscle strain, and its origin on the coracoid is shared with the coracobrachialis, so tenderness at the front of the shoulder can involve either.

Interesting Facts

The short head shares its origin with the coracobrachialis as a "conjoint tendon" on the coracoid process — the same region that anchors the pectoralis minor nearby.

Long head of biceps brachii — the neighbouring biceps belly
Scapula — carries the coracoid process this muscle originates from
Subscapularis — lies deep at the front of the shoulder nearby

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 — Short Head