The hinge is the knee. Although it is a large, heavy-bearing joint, its motion is more restricted than most other joints. It can be bent to 120 degrees, and will straighten to provide stability for the leg. It will not move in any direction. Although the knee has a limited range of motion, it is strong and can withstand side stress. Two cartilage compartments are located in the knee: one inner and one outside. If the cartilage wears unevenly, the…