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Orthopedic Joint Ventures Program
Defining Joint Replacement Surgery

What is total knee replacement?

In order to understand what a total knee replacement is, it is necessary to understand how a healthy knee works.

The knee is the largest joint in the body. It is classified as a hinge joint and works very much like a common hinge. Your knee is made up of three bones: the femur (thigh bone), the tibia (lower leg bone), and the patella (knee cap). Your knee joint connects the femur to the tibia, and on top of this rests the patella. The patella protects the knee joint and slides in a groove found in your femur when you bend your knee. The muscles around the knee are responsible for supporting and moving your knee. It is extremely important to rebuild and strengthen these muscles before and after surgery.

Unfortunately, as a result of years of working, arthritis or trauma, a knee can become painful and less functional. Spurs (small pieces of bone) may deposit in the knee and arthritis may wear away the protective lining between the bones causing a painful grinding of bone on bone.

Conditions that can lead to an unhealthy or painful knee include:

Rheumatoid arthritis
A chronic disease affecting (primarily) the lining of the joint, resulting in destruction and deformity. The cause of rheumatoid arthritis is unknown.
Osteoarthritis
Affects the joint surfaces of weight-bearing joints. Although the exact cause is unknown, it is believed to be caused by abnormal wear and tear to the joint surfaces. Other factors that may contribute to osteoarthritis include age, sex, heredity and obesity. You may eventually lose movement, strength and function of your knee.

At this point, you and your surgeon may make the decision to have your knee replaced with an artificial joint. An artificial knee will function very much like your original knee. Generally speaking, your surgeon will replace the bottom part of the femur and the top of the tibia. In most cases, your surgeon will also decide that your patella needs to be replaced.

Special Questions

It is important for you to have a full understanding of your condition and surgical options. Please ask your surgeon if you have any questions or concerns about your surgery or the implants used to replace your knee. 

What is total hip replacement?

The hip is a ball and socket joint. The “ball” is at the top of your femur (thigh bone) and the “socket” is at the bottom of your pelvis. There is cartilage that covers the head of the femur. This allows the ball to move easily and smoothly in the socket. With the help of the muscles surrounding the hip, you are able to walk easily and without pain.

An unhealthy or painful hip usually results from the wearing away of the cartilage. Without the cartilage, there is no protection between the bony surfaces of the ball and socket. These two bony surfaces become rough and begin grinding against each other. This causes pain that results in stiffness and pain during movement.

Conditions that can lead to an unhealthy or painful hip include:

Rheumatoid arthritis
A chronic disease affecting (primarily) the lining of the joint, resulting in destruction and deformity. The cause of rheumatoid arthritis is unknown.
Osteoarthritis
Affects the joint surfaces of weight bearing joints. Although the exact cause is unknown, it is believed to be caused by abnormal wear and tear to the joint surfaces. Other factors that may contribute to osteoarthritis include age, gender, heredity and obesity.

Other causes of degeneration of the hip include previous hip injury, metabolic bone disease, and abnormalities of growth.

If your surgeon recommends a total hip replacement, he or she will choose the best artificial hip (prosthesis) for you. This prosthesis is usually comprised of four components—a cup, liner, ball and stem. Different types of materials are used to make these components. The cup and stem may be cemented to the bone or porus coated, which allows bone to bond directly to the implant surface.

Ask your surgeon if you have specific questions about your surgery or the types of implants available to replace your hip. The artificial hip will act almost like a healthy hip and should allow for easy, pain-free walking.