The knee joint surfaces are formed by the femur, tibia, and patella (not shown). The surfaces are covered by cartilage.

Certain conditions may indicate the need for a replacement for the knee joint such as: osteoarthritis (shown), persistent knee pain, severe loss of knee function, and certain types of fractures.

A replacement joint can help alleviate pain and improve function. The replacement joint usually has two parts that replace the joint surfaces and is made of a combination of metal and plastic.

Figure 1: Comparison of a normal knee joint and a replacement knee joint.
Figure 2: Normal knee joint.
Figure 3: A damaged knee joint.
Figure 4: Replacement knee joint.