Which muscle flexes the glenohumeral joint?

The muscle that primarily flexes the glenohumeral joint is the coracobrachialis, which originates from the coracoid process of the scapula and inserts on the humerus. Its main function is to assist in flexion and adduction of the arm at the shoulder joint, making it a key player in movements that involve raising the arm forward.

While the deltoids and pectoralis major also contribute to shoulder flexion, their roles are broader, as these muscles are involved in multiple movements (including abduction and internal rotation). The brachialis is primarily a flexor of the elbow joint and does not have a significant action at the glenohumeral joint, which is why it does not align with this question. Understanding the specific roles of these muscles helps clarify why the coracobrachialis is the preferred answer when isolating the flexion at the glenohumeral joint.