Fractures of proximal humerus -Neers classification

1. Lesser tubercle
2. Greater tubercle
3. Anatomical neck
4. Surgical neck

When the arm is raised from the side it assists the Supraspinatus and Infraspinatus in rotating the head of the humerus in the glenoid cavity.
It also holds the head of the bone firmly in contact with the glenoid cavity, and prevents its slipping over its lower edge, or being displaced by the action of the Latissimus dorsi and Pectoralis major, as in climbing and many other movements

The peculiar relations of the tendon of the long head of the Biceps branchii to the shoulder-joint appear to subserve various purposes

1. In the first place, by its connection with both the shoulder and elbow the muscle harmonizes the action of the two joints, and acts as an elastic ligament in all positions
2. It strengthens the upper part of the articular cavity, and prevents the head of the humerus from being pressed up against the acromion, when the Deltoid contracts; it thus fixes the head of the humerus as the center of motion in the glenoid cavity.
3. By its passage along the intertubercular groove it assists in steadying the head of the humerus in the various movements of the arm.