Brachialis muscle

The brachialis is a relatively thick, broad, fusiform-shaped arm muscle responsible for forearm flexion at the elbow joint. It lies in the anterior compartment of the arm. This muscle arises from the humerus immediately distal to the insertion site of the deltoid muscle. It is positioned in the anteroinferior aspect of the arm beneath the biceps brachii muscle and musculocutaneous nerve, extending between the distal anterior humerus and the proximal epiphysis of the ulna. Since it does not attach to the radius, it is not involved in pronation and supination of the forearm and remains unaffected by these movements.