In a total shoulder joint replacement, a metal ball is used to replace the humeral head while the glenoid socket is replaced by a polyethylene cup.

Arthroscopy is a surgical procedure which is used to visualize, diagnose and treat problems within a joint. A small incision is made and a pencil-sized instrument, called the arthroscope, is inserted. The arthroscope contain a small lens and illumination system that magnifies the structures inside the joint. Thus the surgeon is able to see the interior of the joint through a small incision. He is also able to evaluate the type and extent of injury, and then correct the problem. The joints that are treated most frequently with this instrument are the knee, elbow, hip, shoulder, wrist and ankle.

Ligaments are strong, non-elastic connective tissues that encase a joint.

The anterior cruciate ligament (ACL) is a key stabilizing ligament in the knee. Injury is by way of a sprain or a tear.