Muscles stabilizing the clavicle

Subclavius

Subclavius lies entirely beneath the clavicle under cover of pectoralis major. The small, fleshy belly of this muscle attaches to the floor of the subclavian groove on the under surface of the clavicle. The fibres converge and pass medially, becoming tendinous, to attach to the first rib near its junction with the costal cartilage. 

Nerve supply

Subclavius is supplied by the nerve to subclavius, root value C5,6 which arises from the upper trunk of the brachial plexus.

Action

The principal action of subclavius is to steady the clavicle by pulling it towards the disc of the sternoclavicular joint and the sternum during movements of the pectoral girdle. This action tends to depress the lateral end of the clavicle. Paralysis of subclavius has no demonstrable effect.