The Knee JointThe knee is the largest joint in the body and due to its anatomy, our knees bear up to seven times our body weight! The knee joint is where the far end of the femur (thigh bone) meets the near end of the tibia (shin bone). Similar to other joints, the ends of these bones are covered with smooth articular cartilage that allows these bones to move against one another in a smooth and pain-free manner. The knee joint can be thought of as a hinge-type joint, but in reality is much more complex. In addition, the knee joint is made up of a third bone called the patella (often referred to as the knee cap). As the knee bends, the patella moves in a groove in the front of the femur. The undersurface of the patella and the groove in the front of the femur are also covered with articular cartilage. The knee joint is described as being made up of 3 parts (or compartments): the medial (inside), lateral (outside) and patellofemoral (underneath the knee cap) compartments.
Between the femur and tibia are two special types of cartilage structures called menisci which function as additional cushions between the bones. Surrounding the knee are several cushioning sacks of fluid called bursa that protect the joint and can sometimes become inflamed causing localized pain and swelling (bursitis). Finally, the knee is held together by a series of ligaments. The anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), the medial (MCL) and lateral (LCL) collateral ligaments all connect the tibia to the femur and are responsible for joint stability.
As in other joints of the body, arthritis of the knee is caused by break down of the cartilage at the end of the bones, in this case the ends of the femur and tibia, and underneath the kneecap. As this irreplaceable cartilage is worn down, more friction and inflammation leads to worsening symptoms which include pain, stiffness, swelling, weakness, tenderness, and grinding. Many knees will slowly begin to loose function with the inability to fully straighten or bend the knee, and will also appear deformed with knock-knee or bow-legged deformities.
Treatment of Knee Arthritis
Non-operativeNon-operative treatments for arthritis of the knee include physical therapy, weight-loss, exercise, changing one’s activities, using assistive devices, such as a cane, and taking anti-inflammatory medicines. Weight-loss may have a substantial impact on preserving and prolonging the function of the knee. Activity modifications include reducing high-impact and repetitive activities that place increased stresses on the knee joint. Also, avoiding activities that require the knee to bend excessively may help with the symptoms of arthritis. Anti-inflammatory medicines, such as ibuprofen and naprosyn, can reduce the inflammation around the knee joint that is caused by the arthritis and provide significant pain relief.
If these treatments are no longer effective, you maybe a candidate for knee injections with either viscosupplementation (gels) or cortisone (steroid injections). You can read more about Corticosteroid Injections here.
OperativeKnees with significant enough arthritis for surgery are best treated with a knee replacement surgery. Knee replacement surgery consists of resurfacing the diseased ends of the bone with metal and plastic. This procedure removes the arthritis from the knee and allows the knee to return to pain-free function.
Knee replacements are either partial knee replacements or full (total) knee replacements. In a partial knee replacement, only the part of the knee with arthritis is replaced. This can be either the medial (inside of the knee), lateral (outside of the knee), or patellofemoral (under the kneecap) compartments. This procedure only treats the portion of the knee that is replaced, and so if there is arthritis in other parts of the knee, these areas will continue hurt. Because only a small percentage of people with knee arthritis have arthritis confined to only one part of the knee, most people are not candidates for partial knee replacement. This decision should be made in consultation with your orthopaedic surgeon.
Most patients with advanced knee arthritis are candidates for a total knee replacement. In this procedure, the entire end of the femur and tibia are resurfaced with metal and plastic. The undersurface of the patella is often resurfaced as well.
A small incision is made in the center of the knee along the length of the leg. The tissue around the kneecap is carefully incised and the knee cap is slipped onto the side of the knee. The anterior cruciate ligament (ACL) is removed. The ends of both the femur and the tibia are precisely shaped with surgical instruments to accept the replacement components. These components are usually made of cobalt chrome and titanium. Once the appropriate measurements are made, the selected components are placed onto the femur and tibia and held into place with bone cement. A specially shaped plastic polymer made of ultra high weight polyethylene is locked into the tibial piece. The underside of the kneecap is also replaced with ultra high weight polyethylene. Once the bone cement is cured, the kneecap is brought back into place and the tissues are repaired. The total knee replacement is complete.