The lateral head is the most prominent and superficially visible triceps component. Its origin above the spiral groove means its innervation is proximal and is denervated in mid-humeral radial nerve injuries along with brachioradialis.
| Origin | Posterior humerus — above the spiral groove on the lateral side |
|---|---|
| Insertion | Posterior olecranon via the common tendon |
| Nerve Supply | Radial nerve (C6, C7, C8) — branches arising proximal to the spiral groove |
| Blood Supply | Deep brachial artery |
| Actions | Extends the elbow — strongest during eccentric loading (controlling elbow flexion); The most prominent superficial head |
|---|
The lateral head and long head are both denervated in high radial nerve palsies (above the spiral groove), while the medial head may be spared. In posterior arm trauma where the spiral groove is at risk, lateral head weakness confirms high radial nerve injury.
Palpated as the visible lateral posterior arm muscle during resisted elbow extension.
Lateral head triceps weakness accompanying wrist drop in radial nerve injury above the spiral groove, requiring nerve repair or grafting for recovery.
