Subclavius muscle arises from the costochondral junction of the first rib and is inserted into the subclavian groove on the inferior surface of the clavicle, filling the groove completely. The muscle thus lies almost horizontally. It is enclosed by the upper attachment of the clavipectoral fascia.

Nerve supply of subclavius:

By its own nerve from the upper trunk of the brachial plexus (C5 and 6); it runs down from the point of formation of the upper trunk to enter the posterior surface of the muscle.

Action of subclavius:

To stabilize the clavicle in movements of the peripheral parts of the upper limb. It may prevent the jagged ends of a fractured clavicle from damaging the adjacent subclavian vein.