Total knee replacement is one of the most successful of all surgical procedures, and a virtual medical miracle. Prior to the development of total knee replacement technology, patients with advanced arthritis of the knee suffered from chronic pain and loss of functional independence. Following total knee replacement, more than 90% of patients have no pain, or only slight pain, and their walking is no longer limited by their knee. Most patients can live a full and independent life.

The goals of total knee replacement are, in order of priority :

1. pain relief
2. standing and walking that is not limited by the knee
3. improved knee motion
4. improved knee strength

Total knee replacement is major surgery, which usually involves a 3-4 day stay in the hospital and a period of rehabilitation which takes about 3 months. Our team of Orthopaedic Surgeons and their clinical team will work with you to guide your recovery, but you are the most important member of the team! We believe that an informed patient is the best ally in achieving success with total knee replacement surgery. Please read this booklet carefully. Share it with your family and friends. The information here will guide you in preparing for surgery and it will give you insight into how to maximize your recovery from knee replacement surgery and enjoy many years of painless knee function.

Arthritis is a generic condition indicating inflammation of a joint. Inflammation is the general response of the body to injury of any type. The signs of inflammation are pain, swelling, warmth, and sometimes redness. There are many causes of arthritis. These include a sudden, or acute, injury such as might occur when playing sports. Acute trauma is actually the most common cause of arthritis. In most cases, however, the injury does not cause permanent damage, the inflammation subsides over a few weeks, and the joint functions normally for the rest of that person's life. Arthritis can also develop after many years of certain activities performed over and over, which can be considered a form of chronic injury.

The most common form of arthritis, which necessitates knee replacement, is osteoarthritis. In this condition, the articular cartilage, which is the smooth gliding surface of the joint, has worn away. This can occur for a number of reasons. If there is a genetic defect in the quality of the articular cartilage, then this condition is called primary osteoarthritis. Primary osteoarthritis may affect all of the articular cartilage in the body, not just the knees. More frequently, osteoarthritis affects only a few joints, usually in the legs. In these cases, the genetic composition of the articular cartilage is normal, but there is another factor that causes damage to the cartilage in that specific joint or joints. This is called secondary osteoarthritis.

The most common causes of osteoarthritis are related to the alignment of the leg (too bow-legged or too knocked-kneed) and how well the two halves of the knee joint fit together, which is called congruency.

Similar to the tyres on a car, if the leg is not properly aligned, then the surfaces of the knee joint will wear unevenly. Alternatively, if the two sides of the joint do not fit together properly, they will wear unevenly. In some cases people are born with imperfect alignment, and in other cases they develop conditions which result in imperfect alignment of their leg or legs. In other cases, there may have been a disease or an injury that altered the alignment or congruency of the joint (such as an infection, a fracture, or a torn ligament). Increased weight puts more stress on the joint and over time this can cause damage and contribute to a wearing out of the cartilage. Exercise or hard work, without any other factor, does not result in arthritis. Moderate exercise actually improves the condition of joints.

Another common type of arthritis that can affect the knees is rheumatoid arthritis. This type of arthritis is caused by dysfunction of the immune system. Abnormal anti-bodies are produced that get deposited in the lining tissue of the joints (the synovium). This causes chronic inflammation and slow destruction of cartilage. All of the synovial joints of the body may be affected by rheumatoid arthritis and the level of arthritis is roughly equal on both sides of the body, i.e., both the right and the left knees, hands, etc

The knee joint includes the end of the thigh bone (the femur), the top of the leg bone (the tibia) and the knee cap (the patella). The weight of the body is transferred through the femur, across the knee joint, and into the tibia. There are large muscles in the front of the thigh (the quadriceps) that straighten the knee (extension). The large muscles in the back of the thigh (the hamstrings) bend the knee (flexion). The patella functions as an important lever for the quadriceps muscles, making the muscle more efficient. When you bend and straighten your knee, the surfaces of the tibia and femur roll and slide on each other and the patella moves up and down against the front of the femur. Front and side x-ray views of a normal knee are shown in Figures 1a and 1b respectively. The thigh bone (femur) is on the top and the leg bone (tibia) is on the bottom. The smaller bone in the leg is the fibula. The knee cap (patella) can be seen in the front of the knee on the side view. The apparent space between the bones is actually occupied by articular cartilage and is called the joint space. Cartilage is not dense enough to be seen on an x-ray.

Fig 3a Fig 3b The knee is a synovial joint. The tissue lining the joint, called synovium, produces fluid that lubricates and nourishes the surfaces of the joint. The important internal parts of the knee include articular cartilage, meniscal cartilage, ligaments, and tendons. There are two types of cartilage in the knee. Articular cartilage is specialized tissue that covers the ends of the bones. Meniscal cartilage is specialized tissue located around the perimeter of your knee. It helps to distribute the load and provide some stability as well as lubricate the articular cartilage. There are several ligaments (strong bands of fibrous tissue which connect bone to bone) attached to the femur and tibia, which provide stability to the knee. There are also several tendons, which are also strong bands of fibrous tissue, but they attach muscle to bone. It is the force of the quadriceps and hamstring muscles, pulling through tendons, that move the knee and enable you to walk, sit, get up from sitting, climb stairs, etc.

Articular cartilage covers the moving surfaces inside the knee. Articular cartilage is very smooth and has very low friction. Articular cartilage is the "tread" inside your knee. Articular cartilage is living tissue, but it has limited potential for growth and repair. As with all tissue, the potential for growth and repair of articular cartilage decreases with age. If the loads on the joint, or on a portion of the joint, are too high, either because of improper alignment, incongruency, excessive weight, extreme activities, or a combination of these factors, articular cartilage will degenerate and be worn away. The process of articular cartilage degeneration is a source of inflammation. This can result in pain, swelling and progressive loss of motion. In advanced arthritis, the articular cartilage has been completely worn away and the bone of the femur and tibia, and the femur and patella, come into direct contact. This is generally accompanied by significant pain, a decrease in motion (stiffness), muscle weakness, and difficulty walking. The main reason to have a total knee replacement is because of severe pain that is due to extensive loss of articular cartilage.

Wear of articular cartilage can be seen on x-rays as a decrease in the space between the bones. In general, extensive loss of articular cartilage is accompanied by extensive loss of meniscal cartilage. When the cartilage is completely worn away, the x-rays show that the bones are now in direct contact. Loss of articular cartilage increases the amount of stress on the ends of the bones resulting in the growth of bone spurs, or osteophytes, at the margins of the joint. Front and side x-ray views of an arthritic knee are shown in Figures 2a and 2b respectively. On the front view (Figure 2A), note the absence of space between the bones as indicated by the arrows. This loss of joint space occurs because the articular cartilage has worn away. The bone reacts to the loss of cartilage by making bone spurs (osteophytes). These bone spurs can be seen on the side view (Figure 2b) as indicated by the arrows.

Total knee replacement employs specially designed components, or prostheses, made of high strength, biocompatible, metals and plastics, to replace the cartilage in your knee. The metal that is most commonly used is an alloy of cobalt, chromium and molybdenum. The plastic is ultra-high molecular weight polyethylene. These materials have been used in joint replacement for about 30 years and their behavior in the body is well-known. The components are very precisely manufactured and the surfaces are congruent, smooth and highly polished. In this manner, congruent, smooth, low-friction surfaces are restored to the knee.

In modern total knee replacement surgery, only the worn-out cartilage surfaces of the joint are replaced. The entire knee is not actually replaced. The operation is basically a "re-surfacing" (or "re-tread") procedure. Only a small amount of bone is removed, the collateral ligaments are left intact, and the muscles and tendons are left intact. Alignment abnormalities can usually be corrected during the operation by adjusting the direction of the cuts of the bones, removing bone spurs (osteophytes), and lengthening tight ligaments. Front and side views of a knee following total knee replacement are shown in Figures 3a and 3b respectively. Note that the smooth surfaces of the joint are restored. The joint space is now comprised of polyethylene. The operation only replaces the worn surfaces of the joint. The ligaments, tendons and muscles are retained.

Total knee replacement is a major surgical procedure. A tourniquet is usually placed up high around the thigh in order to limit bleeding during the operation. An incision is made in the front of the knee. The large quadriceps muscle covering the front of the femur and knee is moved, temporarily, to one side, in order to expose the surfaces of the knee joint. Specialized instruments are used to trim off the worn-out surfaces and shape the ends of the bones. The femoral component is metallic, and is similar in size and shape to the end of the femur bone (thigh bone). The tibial component, which goes on the top of the leg bone (or tibia), may have a metallic base, but the top surface is always polyethylene. The undersurface of the knee cap (patella) is cut flat and covered with another polyethylene component. Since metal covers the surface of the femur (thigh bone) and polyethylene covers the surfaces of both the tibia (leg bone) and patella (knee cap), total knee replacement involves metal-on-plastic articulation.

The components are attached to the bone with a specialized polymer (polymethylmethacrylate), commonly referred to as "bone cement". Alternatively, some components have a porous texture on their under-surface, into which the bone can grow. This method of attachment is referred to as "porous ingrowth".

Total knee replacement is elective surgery. It is life-enhancing surgery, not life-saving surgery. The decision to undergo total knee replacement surgery is yours. It is important that you be aware of your options, other than total knee replacement surgery. You may simply decide not to have surgery and live with your arthritic knee. In this case, you may choose to avoid strenuous and painful activities. You should, however, adopt some gentle exercise, such as walking. You may benefit from some moist heat, massage or other forms of physical therapy. Weight loss can be very helpful in reducing pain from arthritic knees by reducing the stress, and is good for your general health as well. There are a number of medications, both anti-inflammatory medications and pain medications, that can help you live with arthritis. There are also medicines that can be injected directly into the knee, such as cortisone and newer products that improve lubrication. Unfortunately, the arthritis is progressive in most cases. A cane or a crutch may be required in order to walk.

The following is a list of alternatives to total knee replacement surgery you may wish to explore :

• Specialized Braces
• Arthroscopy
• Cartilage Transplantation
• Osteotomy
• Uni-compartmental arthroplasty
• Arthrodesis or Knee Fusion

Specialized Braces
There are specialized braces that can be helpful in some cases of knee arthritis. These braces are designed to create a force which transfers load from an area of the knee where the cartilage is more worn, to an area of the knee where the cartilage is less worn. These braces are helpful in cases where there is still some cartilage remaining in the knee, and the pressure of the brace causes less discomfort than the knee arthritis.

Arthroscopy
There are less invasive surgical procedures available which can be helpful in some cases. These include arthroscopy. Arthroscopy requires only small incisions around the knee which allow the insertion of small instruments, which are about the size of a pen or pencil. With arthroscopy, degenerated and worn cartilage can be trimmed and smoothed, which reduces the source of inflammation. Additionally, the lining of the knee (the synovium), can be trimmed, and this also decreases inflammation. Patients who have knee arthroscopy almost always go home the same day. Recovery from surgery occurs over a couple of weeks. Unfortunately, the benefit of arthroscopy decreases as the degree of arthritis increases. In advanced arthritis, arthroscopy is of little value.

Cartilage Transplantation
It is now possible to transplant articular cartilage from one location to another. Healthy cartilage, from an area of the knee that does not bear weight, can be transplanted into another area of the knee where weight-bearing cartilage has been damaged. Cartilage transplantation is best for localized areas of damaged cartilage in an otherwise healthy knee. Unfortunately, in most cases of osteoarthritis and rheumatoid arthritis, the degeneration and wear of articular cartilage involves the majority of the joint surfaces. Cartilage transplantation is not a good option in such cases.

Osteotomy
Some cases, where the leg is imperfectly aligned, can be treated by an osteotomy. An osteotomy is an operation that cuts the bone, either above or below the knee, and re-aligns the knee to a better position. This is a bigger operation than an arthroscopy and patients usually stay 1 or 2 days in the hospital. It takes 6 to 8 weeks for the bone to heal. Physical therapy is usually required to restore knee motion and strength. Complete recovery takes a number of months. An osteotomy is a good operation, especially for younger patients, and those where the leg is clearly not straight and the cartilage wear is confined to one portion of the knee. Unfortunately, the success of an osteotomy decreases as the degree of arthritis increases.

Uni-Compartmental Arthroplasty
In a few cases, only a portion of the knee joint surfaces have worn out and need to the replaced. When only a portion of the knee is replaced, this is called a uni-compartmental arthroplasty. Patients usually stay 2 or 3 days in the hospital and it takes a couple of months for the knee to recover. Physical therapy is usually required to restore knee motion and strength. Unfortunately, in most cases of arthritis, the joint surfaces are diffusely worn. Uni-compartmental arthroplasty is, therefore, less commonly performed than total knee replacement.

Arthrodesis / Knee Fusion
In cases when the risk of failure of total knee replacement is considered to be very high, an arthrodesis, or knee fusion may be recommended instead. In this operation, the ends of the femur and tibia bones are cut flat, the cut ends are pressed together such that the leg is just slightly bent, and then held in this position by pins, or plates and screws. Over a couple of months the ends of the bones grow together, hence the term knee fusion. The knee fuses in a nearly straight position and cannot be bent. Although the knee no longer moves, it is not painful and most patients walk with only a slight limp.

Total knee replacement is a major surgical procedure and there are innumerable potential complications. In aggregate, the benefits (improvement in the patient's quality of life) of total knee replacement outweigh the risks (the chance of that patient having a complication) for most individuals with severe knee arthritis. Most patients have many years of painless knee function. If you wish to receive the benefits of total knee replacement, you must also be willing to accept the risks. The decision to undergo total knee replacement surgery is yours.