The long head originates on the supraglenoid tubercle just above the shoulder joint from where its tendon passes down along the intertubercular groove of the humerus into the joint capsule of the shoulder joint. [1] When the humerus is in motion, the tendon of the long head is held firmly in place in the intertubercular groove by the greater and lesser tubercles and the overlying transverse humeral ligament. During the motion from external to internal rotation, the tendon is forced medially against the lesser tubercle and superiorly against the transverse ligament. [ http://en.wikipedia.org/wiki/Biceps_brachii_muscle#Origin_and_insertion ]