Total Knee Replacement
Total knee replacement, also called total knee arthroplasty, is a surgical procedure in which the worn out or damaged surfaces of the knee joint are removed and replaced with artificial parts. The knee is made up of the femur (thigh bone), the tibia (shin bone), and patella (kneecap). Joint surface cartilage provides a lubricating and shock-absorbing layer over these bone surfaces. The meniscus, the soft cartilage between the femur and tibia, also serves as a cushion and helps absorb shock during motion. Arthritis (inflammation of the joints), injury, or other diseases of the joint can damage the protective layer of joint cartilage and the meniscal cartilages, causing extreme pain and difficulty in performing daily activities. Your doctor may recommend surgery if non-surgical treatment options have failed to relieve the symptoms.
Indications
Total knee replacement surgery is commonly indicated for severe osteoarthritis of the knee. Osteoarthritis is the most common form of knee arthritis in which the joint cartilage gradually wears away. It often affects older people.
In a normal joint, articular cartilage allows for smooth movement within the joint, whereas in an arthritic knee the cartilage itself becomes thinner or completely absent. In addition, the bones become thicker around the edges of the joint and may form bony “spurs”. These factors can cause pain and restricted range of motion in the joint.
Your doctor may advise total knee replacement if you have:
- Severe knee pain which limits your daily activities (such as walking, getting up from a chair or climbing stairs).
- Moderate to severe pain that occurs during rest or awakens you at night.
- Chronic knee inflammation and swelling that is not relieved with rest or medications
- Failure to obtain pain relief from medications, injections, physical therapy, or other conservative treatments.
- A bow-legged or knocked-knee deformity
Causes
The exact cause of osteoarthritis is not known, however there are several factors that are commonly associated with the onset of arthritis and may include:
- Injury or trauma to the joint
- Fractures at the knee joint
- Increased body weight
- Repetitive micro-injury and overuse
- Joint infection
- Inflammation of the joint
- Connective tissue disorders
- Genetics
Diagnosis
Your doctor will diagnose osteoarthritis based on the medical history, physical examination, and X-rays. MRI is occasionally used, but is rarely necessary to make a diagnosis of severe arthritis.
X-rays typically show a narrowing of the joint space in the arthritic knee.
Benefits
If your arthritis is such that you have significant pain, deformity and reduction of mobility, you are in your 70’s, and are keen on reasonable, yet not excessive activity, you have a good chance of improvement in comfort and function with a knee replacement. Younger, active people with less severe arthritis are less likely to be happy with the outcome of knee replacement, and have a higher chance of needing revision surgery later in life.
Procedure
The goal of total knee replacement surgery is to relieve pain and restore the alignment and function of your knee.
The surgery is performed under spinal or general anaesthesia. High-dose antibiotics are administered by the anaesthetist. A tourniquet is used for a short time only, if one or more of the components is to be cemented in place. A foot-compression device is utilised on the non-operated leg to reduce blood-clotting risk. An incision is made in the skin over the affected knee to expose the knee joint. Temporary computer-alignment pins are inserted into the femur and the tibia to allow accurate bone cuts and alignment. Appropriate amounts of bone are removed from the ends of the tibia and the femur, and the prostheses are inserted. These components may be uncemented – designed for your bones to grow onto them for long-term fixation, or they may be cemented in place. There are pros and cons to each technique, and treatment is individualised to the person. A plastic insert is placed between the femoral and tibial components to act as a spacer bearing. The patella may, or may not be resurfaced. There is contention in current literature regarding patella resurfacing. We must always think of the future, and of the small risk of needing a second operation on the knee. Whilst modern orthopaedic surgery has good options available for revision of the femoral and tibial components if required, it has no good options for a failed patella component should that also require revision. Providing the femoral component is designed to be ‘friendly’ to the person’s own native patella, there is a good case to leave the patella un-resurfaced. With all the new components in place, the knee joint is tested through its range of motion, to ensure appropriate stability and alignment through all ranges of motion. The entire joint is then irrigated and cleaned with a sterile solution. Long-acting local anaesthetic is injected into the joint capsule. The incision is carefully closed. Drains are not used, as they have not been shown to be of benefit. A sterile dressing is placed over the incision and the knee is gently bent over a pillow (this reduces bleeding into the knee in the first few hours after surgery). A foot compression device is placed on the operated leg, to reduce clotting risk. Ice may be applied.
You are then taken to the recovery bay, and after 30 to 60 minutes, transferred back to the surgical ward, or high-dependency unit.
Post-Operative Care
Most people will stand and walk with the physiotherapist three to five hours following surgery. This is initially using a wheeled frame, and subsequently using crutches. The physiotherapist also teaches you specific exercises to strengthen your leg and restore knee movement.
Ice is often applied, and pain relief given as needed. Elevation is recommended whenever resting, to reduce the amount of swelling.
Discharge from hospital is achieved when you are able to utilise crutches to go up and down stairs safely. This often between days two and four post-operatively. Transfer to the rehabilitation is occasionally required for those people who are frail, or have particularly demanding home environments.
Risks and Complications
As with any major surgery, possible risks and complications associated with total knee replacement surgery include:
- Death: 1 in 1000 for younger, healthier patients. 1 in 100 for older patients, or those with multiple co-morbidities
- Dissatisfaction with the outcome. 1 in 10 people actively dislike their knee replacement. These are world-wide figures.
- Knee stiffness
- Infection – approximately 1 in 250. Higher rates noted for people with diabetes and other chronic diseases.
- Blood clots (deep vein thrombosis)
- Nerve and blood vessel damage
- Ligament injuries
- Patella (kneecap) dislocation
- Component wear requiring revision surgery.
- Loosening of the implant
