Though the shoulder is often considered a unit, it is actually comprised of many joints. The shoulder joint is joined by tendons and muscles, which permit the joint to move in many directions. Of all the joints in the human body, the shoulder has the greatest range of motion.

The most common shoulder problems are instability (dislocation), fractures, arthritis, and tendon inflammation. Shoulder injuries manifest in the following ways: swelling, pain, open wounds, stiffness, weakness, popping noises, and lack of flexibility.

A large percentage of elbow injuries are related to repetitive stress. Repetitive stress injuries often go undetected until symptoms become debilitating. Repeated stress or strain placed on the elbow joint can result in micro trauma to the bone, muscle, or tendon. Tenderness, stiffness, tingling, cramping, and muscle weakness are all possible symptoms of a repetitive stress injury.

It would be impossible to extend your arm or retract it without the use of your shoulder or elbow. It would also be very hard to do many of the things that come easily to most people (e.g. lift, pull, and push).