Explore Total Knee Replacement

Your Knee

The knee joint connects the femur (thigh bone) and the tibia (shin bone). The knee can be thought of as a simple hinge-type joint permitting you to extend (straighten) and flex (bend) your knee. The actual movements of the knee are more complex and include rolling, pivoting, and small rotations on either side.

Similar to other joints, smooth articular cartilage covers the ends of these bones; uniquely in the knee, cartilaginous disks called menisci (singular: meniscus) further cushion and protect the knee. The combination of the articular cartilage and the menisci permits the knee bones to glide smoothly and effortlessly through motions of standing, sitting, jumping, running and taking stairs. Taking stairs and running for example, can exert 5-7 times your body weight on the knee joint.

The knee also has the patella bone (knee cap). The undersurface of the patella is covered with smooth articular cartilage, permitting it to easily slide up and down in a furrow on the femur and protects the inner ligaments of the knee.

As you can see in the accompanying image, the femur bone ends in two distinct half-doughnut shaped condyles: the medial (inside) condyle and the lateral (outside) condyle. In some patients, surgery may be performed under only one of the condyles or components (see partial/unicompartmental knee surgery).

Knee Arthritis

As in other joints, arthritis of the knee is caused by wear-and-tear of the cartilage at the end of the bones – in this case the ends of the femur and tibia, and underneath the kneecap. As the cartilage wears away, the bone ends rub against each other causing the grinding, accompanied by pain and swelling. As the arthritis progresses, there may be swelling around the knee, tenderness, stiffness and pain with the inability to straighten the knee. In severe cases, the knee may appear deformed with knock-knee or bow-legged deformities.

Arthritis is the most common cause of the breakdown of knee cartilage.

Osteoarthritis: also referred to as “wear and tear” arthritis; osteoarthritis affects the cartilage that cushions the ends of the knee bones. As this cartilage wears away, the ends of the bones rub together (bone-on-bone) causing a grinding feeling, knee pain and resulting stiffness.

Rheumatoid Arthritis: a systemic disease, which affects multiple joints in the body. The synovial membrane, which lines the entire joint cavity becomes irritated and produces too much fluid. The resulting healing response damages the cartilage, leading to pain and stiffness. Rheumatoid arthritis starts in much younger patients.

Mass General’s Department of Orthopaedic Surgery offers patients of all ages advanced surgical and non-surgical treatments for osteoarthritis and joint pain.


Non-Surgical Treatment

In most cases, non-surgical treatments are exhausted before operative measures are considered, including:

  • Physical therapy
  • Weight loss
  • Modifying your activities
  • Using assistive devices, such as a cane
  • Anti-inflammatory medicines

Physical therapy and exercise can help keep your joints flexible, strengthens the muscles around the joints, reduces pain and keeps your bone and cartilage tissue strong and healthy. If you start an exercise regimen, take a balanced approach and include aerobic activities such as walking, swimming and cycling in addition to stretching/flexibility exercises and strengthening exercises. You want to avoid exercises that place excessive stress on the joints like high-impact workouts or competitive sports activities.

Losing weight can have a surprising effect on reducing arthritic pain. With each step, you exert 4-7 times your body weight on your knee joints. So when you lose even a small amount of weight, your symptoms improve dramatically and you may be able to perform more activities and potentially put off surgery for six months or longer.

Activity modifications include reducing high-impact and repetitive activities that place increased stresses on the knee joint. Guided yoga or pilates can also help reduce pain and improve mobility.

The use of a cane, usually in the hand opposite the affected knee, can reduce the stress across the knee joint. Anti-inflammatory medicines, such as ibuprofen and naproxen, can reduce the inflammation around the knee joint that is caused by the arthritis and provide significant pain relief.

If all non-operative treatments have been attempted and fail to reduce pain, then surgery to replace the knee joint is the last option.

Surgical Treatment

Total knee replacement (TKR) is performed in patients with severe loss of knee cartilage due to injury or inflammation, wear and tear due to various types of arthritis or other aging-related changes in the knee.

In TKR, the worn cartilage is surgically removed and replaced with combination of metal and plastic implants.

Revision TKR

Total knee replacement implants have a normal life span of 10-20 years. With time, the artificial components also wear out and will need to be replaced in a “revision” TKR procedure. Implants may also need replacement for infection, pain or other factors as determined by your doctor.

Partial Knee Replacement (Unicompartmental Knee Replacement)

In some cases, wear and tear of the knee or arthritis is confined to a single compartment (or condyle) of the knee. If your doctor determines it appropriate for your individual case, then only the damaged compartment of the knee may be replaced and the healthy compartment of the knee is left alone. This is referred to as a partial knee replacement, and is only applicable to a small number of patients.

Because a partial knee replacement is done through a smaller incision, the surgery is quicker, the hospital stay is shorter, and patients can rehabilitate and return to normal activities faster.

Video: Surgical Outcomes for the Knee