Pain with overhead activities or pressure on the upper, outer arm are symptoms. Shoulder bursitis: Inflammation of the bursa, the small sac of fluid that rests over the rotator cuff tendons.Shoulder tendonitis: Inflammation of one of the tendons in the shoulder's rotator cuff.Raising the arm causes pain and a 'popping' sensation if the shoulder is dislocated. Shoulder dislocation: The humerus or one of the other bones in the shoulder slips out of position.If inflammation or an injury in the rotator cuff is present, this impingement causes pain. Shoulder impingement: The acromion (edge of the scapula) presses on the rotator cuff as the arm is lifted.A rotator cuff tear may be a sudden injury, or result from steady overuse. Rotator cuff tear: A tear in one of the muscles or tendons surrounding the top of the humerus.The shoulder is an uncommon location for gout. Gout: A form of arthritis in which crystals form in the joints, causing inflammation and pain.Rheumatoid arthritis can affect any joint, including the shoulder. Rheumatoid arthritis: A form of arthritis in which the immune system attacks the joints, causing inflammation and pain.The shoulder is less often affected by osteoarthritis than the knee. Osteoarthritis: The common 'wear-and-tear' arthritis that occurs with aging.As a frozen shoulder progresses, movement in the shoulder can be severely limited. Frozen shoulder: Inflammation develops in the shoulder that causes pain and stiffness.This gives the shoulder a wide range of motion, but also makes it vulnerable to injury.

The humerus fits relatively loosely into the shoulder joint.

A cuff of cartilage called the labrum forms a cup for the ball-like head of the humerus to fit into.

The bursa is a small sac of fluid that cushions and protects the tendons of the rotator cuff.

The rotator cuff is a collection of muscles and tendons that surround the shoulder, giving it support and allowing a wide range of motion.

The shoulder has several other important structures: The coracoid process is a hook-like bony projection from the scapula.The clavicle (collarbone) meets the acromion in the acromioclavicular joint.The acromion is a bony projection off the scapula.Other important bones in the shoulder include: The shoulder joint is formed where the humerus (upper arm bone) fits into the scapula (shoulder blade), like a ball and socket. The shoulder is one of the largest and most complex joints in the body.

Look over the shoulder towards the rear