Short head of biceps brachii

Caput breve musculi bicipitis brachii · Krátká hlava dvojhlavého svalu pažního

Muscles

Looks like

The inner head of the biceps, starting from a hook of bone on the front of the shoulder blade (coracoid).

Bends the elbow and turns the palm up; helps bring the arm forward.

Powered by the musculocutaneous nerve. A sudden pop at the elbow with bruising may be a tendon tear there; see a doctor within days.