Shoulder forward flexion is mainly performed by contraction of the pectoralis major, anterior deltoid, biceps, and rostro-humeral muscles.
1. Pectoralis major: Pectoralis major belongs to the upper thoracic limb muscle, which has the effect of making the shoulder joint adduction, rotation and forward flexion.
2. Anterior deltoid muscle: the deltoid muscle is located in the shoulder and can be divided into the anterior, middle and posterior bundles, and the contraction of the anterior bundle can make the shoulder joint flex and rotate internally.
3. Biceps brachii muscle: Biceps brachii muscle starts from the superior glenoid tubercle of scapula and the rostral eminence of scapula, and ends at the radial tuberosity, which can flex the elbow joint and assist in the anterior flexion of the shoulder joint.
4. Rhabdomyoclavicular muscle: Rhabdomyoclavicular muscle starts from the rostral process of scapula and stops at the middle of humerus on the medial side, when contracted, it can make the shoulder joint forward flexion and adduction.
The forward flexion of the shoulder joint also requires the movement of the humerus, scapula and other bony structures as well as the joints, and the contraction of the muscle is the power source of the forward flexion of the shoulder joint, and the forward flexion of the shoulder joint may be affected when the above mentioned muscles are injured.