TOTAL KNEE REPLACEMENT
ARTHRITIS OF THE KNEE
The knee joint is lined by articular cartilage, a specialised lining which allows smooth pain free motion of the joint. Arthritis is a degeneration or wearing out of this lining which results in the bone ends rubbing on one another rather than the articular cartilage. This causes pain. The two most common forms are osteoarthritis and inflammatory arthritis.
WHAT CAUSES ARTHRITIS?
Osteoarthritis is very common. The exact cause is unknown and can occur for no apparent reason other than general wear and tear. It may result from a number of conditions the most common of which are:
- Avascular necrosis
- Certain diseases of bone and connective tissue
- Malalignment of the leg (knock knee or bow leg)
Inflammatory arthritis, the most common of which is rheumatoid arthritis, is an immune disorder whereby there is inflammation of the synovial lining of the joint which releases chemicals or enzymes into the joint resulting in damage to the lining (articular surface). This condition can affect any synovial joint in the body and is best treated medically by a rheumatologist. Only when there is severe damage to the knee joint is joint replacement required.
WHAT ARE THE SYMPTOMS?
- Pain which is usually of gradual onset but can be sudden. The pain can be localised to one area in the joint or be all around the knee.
- Stiffness making it difficult to straighten or bend the knee
- Limitation of walking either due to pain or fatigue
- Grinding or clicking
- Giving way
- Deformity, including the leg can change shape (become more bow legged or knock kneed)
HOW IS IT DIAGNOSED?
- Osteoarthritis is diagnosed on history, physical examination and x-ray.
- Physical examination will reveal pain on moving the joint and limitation of movement as well as palpable bony prominences (osteophytes).
- X-rays will reveal narrowing of the joint space and often deformity of the bones and new bone formation (osteophytes).
- Blood tests are useful in inflammatory arthritis.
WHAT IS THE TREATMENT?
- Simple analgesia
- Anti-inflammatories supervised by local doctor
- Use of a walking stick in the opposite hand to take weight off the knee
- Weight loss
- Maintenance of fitness and muscle tone
- Special medications for inflammatory arthritis
- Shoe inserts to absorb shock
- Corticosteroid injections. These are injected into the joint to settle down inflammation and can be of use in an arthritic knee, especially one which is not bad enough to require a knee replacement. Repeated injections can have deleterious effects on the joint and there is a small risk of infection with any joint injection.
- Glucosamine and chondroitin sulfate tablets. These are sold over the counter. Studies are under way to test their effectiveness but currently there is no strong scientific evidence supporting their effectiveness
- Hyaluronic acid injections- these are a series of injections which assist in lubrication of the joint. Any benefit is short term and their use is controversial and they are very expensive.
- Arthroscopy: this can help in early arthritis especially with sudden onset of symptoms. Often there is an associated meniscal tear which can be debrided and loose flaps of cartilage (lining of the joint) can also be debrided. An arthroscopy is useful in a knee that is not bad enough to warrant a replacement.
- Osteotomy: an operation to cut the bone realign it so that more weight is taken on the healthy part of the joint. It is particularly helpful in young active patients who are not suitable for a joint replacement.
- Cartilage transplant: this may be beneficial in well localised lesions in young patients
- Joint replacement: this can be either a partial or a full knee replacement depending on symptoms and x-ray signs.
TOTAL KNEE REPLACEMENT
Total knee replacement is a “quality of life” operation. There is an essential need for a comprehensive history to assess the patient’s pain and general disability. If the pain and disability are severe or the patient cannot tolerate the pain any more or is not prepared to, then joint replacement is offered to the patient.
The age at which total knee replacement is being done is becoming progressively younger, but we prefer to operate on patients over 65. We can expect over 90% for a 15-year survival in joint replacements.
This is very similar as for total hip replacement but we have other alternatives such as, a high tibial osteotomy and unicompartmental knee replacement. In general, the best figures for survival for unicompartmental knee replacement are 80% for 8-year survival.
People that require unicompartmental knee replacement are people with:
- Medial or lateral compartment disease only
- Over 60 years of age
- Less than 82kg
- Less than 10 degrees of fixed flexion and flexion over 100 degrees.
- If they have a cruciate deficient knee, they are not suitable for unicompartmental knee replacement.
WHAT TYPE OF JOINT?
The type of joint replacement used varies from surgeon to surgeon and may, in the future, be dictated by cost constraints.
In general, most surgeons are doing uncemented joint replacements in the younger group of joint replacement candidates. Dr Walker tends to use uncemented joint replacements in patients younger than 70 based on their physiological rather than their chronological age.
Uncemented joint replacements rely on a “press fit” and rely on an irregular surface (e.g. titanium mesh) or a bioactive surface (e.g. hydroxy-apatite) to ensure ingrowth of bone into the prosthesis. This is augmented with flanges, stems and, in the case of the tibia, screws.
The patient is up walking at Day 1 or 2 on a frame, progresses to crutches and then a stick by 3 weeks. The use of the stick will continue until the patient is confident. Most total knee replacement patients require physiotherapy post operatively.
About 10% of total knee replacements are manipulated if their range of motion is not past 90 degrees at six weeks.
COMPLICATIONS AT HOME
The early post-operative complications are:
Early increase in pain, erythema around the wound or significant swelling of the wound are all good reasons to refer the patient straight back to the treating surgeon. If a very early appointment is not available with the surgeon, the patient should be sent straight to casualty. Calf pain, swelling of the ankle or calf should be investigated urgently. Chest symptoms should be investigated for a pulmonary embolism. Dr Walker recommends duplex ultrasound for the leg and ventilation perfusion scan or spiral CT scan for the chest.
In the long term, the major complications are:
If the patient develops pain in their knee of a relatively quick onset this should be treated as suspected infection and investigated. It is very important to the patient’s primary treating physician that, if the patient has any operative or dental procedures, they are covered by suitable antibiotics. This is because bacteria seeding into the joint from any bacteraemia is possible.
Loosening can occur at any time and this is why the patient should be seen by their orthopaedic surgeon every second to third year after the initial rehabilitation phase. X-rays may pick up changes which do not become symptomatic for a significant period of time.
In general, we are getting over 90% for a 15-year survival with our modern knee replacements. Some surgeons are using ceramic femoral components which will lead to longer life of the prosthesis.
Most patients return to sedentary jobs at 3-6 months after total knee replacement. It must be stressed to the patient before surgery that they may not return to manual labour after joint replacement. Any heavy manual job will result in premature loosening of the joint replacement and pain due to the increased stress on the joint replacement. However, clerical or supervisory duties are suitable for a patient with a total knee replacement.
Obviously, pounding sports (e.g. jogging) are not good for joint replacement as they can wear the articulation. Recommended exercise alternatives include; regular walking, bushwalking, swimming, stationary bike riding, doubles tennis and skiing on groomed runs if the patient is already a good skier. Jogging and heavy weights, although possible, will wear the joint prematurely.
POST-OPERATIVE SEXUAL INTERCOURSE
Sexual intercourse is allowed when the patient is comfortable, but they have to be in charge of the positions used. Any significant discomfort should result in the patient abstaining. In general, sexual intercourse occurs at around 3 – 6 weeks post operatively.