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The shoulder refers to the group of structures in the region of the joint where the humerus bone fits into the scapula in a ball and socket formation.  This is one of the most complex joints of the body made up of three bones and many associated muscles, ligaments and tendons.

Structures of the shoulder:

  • Clavicle: Collarbone
  • Scapula: Shoulder blade
  • Humerus: Upper arm bone
  • Acromion: Bony projection off the scapula.
  • Rotator Cuff: Muscles and tendons that surround the shoulder, giving support and wide range of motion.
  • Bursa: Small sac of fluid that cushions and protects the tendons of the rotator cuff.
  • Labrum: Cartilage that forms a cup in which the head of the humerus fits.

The humerus fits loosely in the joint and that makes the shoulder flexible for the wide range of motion required in the arms and hands and also strong enough to allow for actions such as lifting, pushing and pulling.