Knee Replacement

Anatomy of the knee joint

The knee joint, surrounding muscles and tissue are important structures in carrying out day to day activities. The knee joint is a complex hinge formed between the large thigh bone called the femur and the large shin bone, called the tibia, covered by the knee cap or patella.

The main muscles spanning the knee joint include the front thigh muscles or quadriceps and the back thigh muscles, the hamstrings. The knee joint is assisted by the other joints of the leg and pelvis as well as the muscles of the entire lower limb and body’s trunk or core. There are a number of mechanisms that can cause the knee joint to become damaged or weakened, ultimately leading to arthritis.

Arthritis is damage to the boney surfaces that form the joint. It causes pain, stiffness and deformity. Arthritis of the knee makes it difficult walk, get up from a chair, kneel or squat, climb stairs among other activities. As it worsens, arthritis can even cause pain at rest or at night. Arthritis can be hereditary or caused by injury or obesity, however its affects can be lessened by a healthy and active lifestyle.

Knee replacement involves removing the damaged surfaces of the knee joint and replacing them with artificial components called prostheses (Watch a Knee Replacement Video). With the aid of rehabilitation, a knee replacement can reduce pain, improve mobility, strength and function resulting in a better quality of life.

Research has shown that joint replacement is very effective at achieving these outcomes in most people. For persons who are physically and emotionally ready for Joint Replacement, there is roughly an 80% chance of being satisfied with the outcomes of surgery. For the remaining 20% there are some known and many unknown reasons for less than ideal results. Complications such as infection or blood clots do occur in less than 1% of patients and can lead to poorer surgical outcomes and prolonged recovery. Other important factors such as realistic expectations and sufficient recovery of function are also very important. It is important to understand your particular risk level for surgical complications and what you can expect after surgery along with the efforts you will undertake to restore your quality of life. Talk to your surgeon about your risk levels, expectation and rehabilitation as it will assist with your decision making for surgery.

There are a variety of non-surgical treatment options that should be considered before proceeding with a joint replacement.

Weight Loss

For both the hip and the knee, the forces acting across the joint are a combination of body weight pressing down on the joint and the muscles pulling up to stabilize the joint. As these values combine, the hip and knee experience 3-4 times the body weight in pressure with each step. Loosing excess weight reduces the pressure on damaged joints and can relieve pain.

Physical Therapy

By stretching, strengthening and re-balancing the muscle- forces across the joint, the movement and control of the joint can be improve. Pain can also be improved with therapy in addition to the mobility of the joint.

Acetaminophen

Acetaminophen (Tylenol) containing products can be very useful analgesics in arthritis. Given its low cost and good side effect profile, it is a good first-line drug for treating arthritis. It should be avoided in some patients with a history of liver disease and care should be taken not to exceed the total daily dose of 4gm per day. This is especially true when a patient takes multiple different medications that contain acetaminophen.

NSAIDs

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are medications that block the COX receptors on cells and reduce inflammation which can play a significant role in both osteoarthritis as well as other inflammatory arthridities such and rheumatoid arthritis and lupus. Different versions of this type of drug have different side-effect profiles, but, in general, NSAIDS, when taken for extended periods, can play a role in stomach irritation, ulcers, and bleeding and kidney problems with elevated blood pressure. While these can be very helpful medications, their prolonged use should be done under the guidance of a physician.

Steroid Injections

Steroid injection (often referred to as a “cortisone shot”) is generally performed with a depot version of a corticosteroid that remains within the joint. Once in the joint, the steroid blunts the inflammation within the joint and can reduce the pain of the arthritis. This effect can last from a few days to 6 months. There is a small risk of infection with an injection which can be very debilitating and destructive if it were to happen. The risk of infection is less than 1%. There is no agreed upon number as to how many times an injection can be repeated if the most recent injection had benefit for multiple months. Most agree that multiple injections can be offered, the whether a limit should exist or how high the limit may be is unknown.

Unloader Bracing

As arthritis progresses in the knee and joint space is lost, the leg becomes more bow-legged or knock-kneed. As this collapse occurs, increased load is applied to the already diseased and damaged section of the joint. By applying and unloader brace, the leg can be straightened and the load shifted back onto the more healthy area of cartilage remaining. This can reduce pain and suffering during activities such as walking, shopping and yard-work.

Viscosupplement Injection

Viscosupplement injections inject a purified, viscous fluid into the joint. The injection frequently includes components of normal healthy joint fluid known to be reduced in arthritis. While the exact mechanism of benefit is not known, many patients, especially with early arthritis, can benefit from these injections for a variable period of time.

Walking Aid

Many patients find the use of a cane, walking stick or walker to reduce their pain. By transferring weight to the walking aid, the effected joint can be off-loaded reducing the pain experienced and improving the distance that a patient can walk.