Medial Head of Triceps Detail

caput mediale m. tricipitis brachii detail

The medial head is the most deeply placed and most consistently active of the three triceps heads. Its distal radial nerve supply means it is spared in mid-humeral radial nerve palsy (the "wrist drop" injury at the spiral groove).

Nerve: Radial nerve (C6, C7, C8) — branches arising… Blood Supply: Deep brachial artery Region: Upper Arm

Anatomical Data

Origin, Insertion & Supply

Origin	Posterior humerus — below the spiral groove on the medial side
Insertion	Posterior olecranon via the common tendon
Nerve Supply	Radial nerve (C6, C7, C8) — branches arising distal to the spiral groove
Blood Supply	Deep brachial artery

Biomechanics

Function & Actions

Actions	Extends the elbow — active through the full range of extension; The deepest and most tonically active head — remains active even during gentle elbow extension

Clinical Relevance

Clinical Notes

The medial head's distal radial nerve supply (below the spiral groove) means it is tested in radial nerve injury localisation — preserved medial head (elbow extension) with absent brachioradialis (proximal radial nerve) indicates an injury above the brachioradialis branch. The anconeus (which shares the elbow extension function) also has a distal radial nerve supply.

Palpation

Palpated as the deep medial posterior arm muscle during gentle resisted elbow extension.

Pathology

Common Injuries & Conditions

Medial Head Preservation in Mid-Humeral Radial Nerve Palsy

Preserved medial head elbow extension despite wrist drop in spiral groove radial nerve palsy, localising the lesion to the mid-humerus distal to the medial head branches.