Overview
It arises on the caudal surface of the proximal humerus and spirals down the brachial groove (sulcus musculi brachialis) to the cranial side of the elbow, where it passes under the biceps tendon and ends on the medial surface of the radius.
Origin
Caudal surface of the proximal humerus, distal to the head.
Insertion
Proximal end of the radius, on its medial surface.
Action
Flexes the elbow.
Innervation
Musculocutaneous nerve (n. musculocutaneus).
Clinical relevance
The radial nerve accompanies this muscle in the brachial groove and crosses the lateral surface of the arm. It can be injured in fractures of the humeral shaft or by compression during general anaesthesia in lateral recumbency. The horse shows a dropped elbow: it cannot extend the elbow, carpus or fetlock and bears weight poorly on the hoof.