This website has been written by the Orthopaedic and Therapies staff at the Royal Liverpool & Broadgreen University Hospitals NHS Trust in partnership with the Joint Replacement Network. All information contained in this booklet is the property of the Royal Liverpool and Broadgreen Hospitals and can not be reproduced without express permission.

It has been designed to guide you and your family and friends, through the process of having a knee replacement and your rehabilitation afterwards.

Remember, each person is an individual and particular instructions and details may vary from one person to another - this depends on the type of prosthesis used and/or the surgeon’s preference. Your rehabilitation will be aimed at your individual needs.

What are the benefits of having a knee replacement?

The aim of the operation is to replace or resurface your painful arthritic knee joint with an artificial joint (called prosthesis). Once your new joint has completely healed you should experience one or more of the following benefits

• Reduced or no pain

• Increased movement and mobility

• Correction of angular leg deformity

• Increased leg strength (if you exercise!)

• Improved quality of life, and being able to return to most normal activities and pastimes.

The Knee

To understand the total knee joint procedure you need to know how the knee is constructed and how it works. The knee is a hinge like joint, which unites your two leg bones, the femur (t highbone) and the tibia (shinbone). The front of the knee joint is protected by the patella (kneecap), which articulates with the femur (patello-femoral joint). Inside the joint, bone ends are covered with a smooth tissue called articular cartilage. The joint is lined with a synovial membrane, which produces synovial fluid (joint nutrient and lubricant).

In a normal knee, smooth weight bearing surfaces allow free painless movement. Muscles and ligaments give you power to move the joint and provide stability. The normal movement of the knee depends on joint fluid and smooth healthy articular cartilage, as well as strength and flexibility of the surrounding muscles and ligaments. Sitting, standing and walking depend on the bending and straightening of the leg at the knee joint. (The Normal Knee Joint above)

What is Osteoarthritis (OA)?

Knee pain and stiffness often results from osteoarthritis (wear and tear of joint articular cartilage and bone), rheumatoid arthritis (an inflammatory joint disease) or an injury. Arthritis causes your articular cartilage to wear away. As a result of this the bone ends become rough and rub together causing pain. Your joint may also be inflamed and swollen.

The causes of osteoarthritis are not well documented. Although ageing is the factor most strongly associated with OA, it is important to understand that OA is not an inevitable consequence of ageing. Osteoarthritis is a slowly progressive condition. However, previous injuries and consequent damage to articular cartilage will result in accelerated osteoarthritis. There may be a genetic tendency in some people that increases chances of developing osteoarthritis.

The Knee in Osteoarthritis

Of the three surfaces (tibia/femur/patella) in your knee that may become roughened and painful you may need two or all three surfaces replaced. Like a normal knee, your prosthesis will have smooth weight bearing surfaces.

Total Knee Replacement

The metal femoral component covers the end of your thighbone and the tibial (metal and plastic) component covers the top of your shinbone. The patella (knee cap) may or may not be resurfaced with a plastic button. (Osteoarthritis Knee left)

What materials are used for implants?

Joint implant manufacturers, orthopaedic surgeons and scientists continually strive to improve the durability of these devices.

Current scientific advances in metallurgy have resulted in the use of cobalt-chrome alloys and zirconia oxide, which are used for the femoral component. The tibial component is made of ultra-high molecular weight polyethylene, which is very durable, but will eventually wear out. Orthopaedic companies have been working hard to find better materials that will not wear out for a long time. The studies of modern knee arthroplasty report clinical survival of up to 96% of total knee implants at 10 to 15 years. The overall success of total knee replacements lies in an understanding of the relationship between implant design, surgical technique and patient’s lifestyle.

If you think you are sensitive to nickel please tell your doctor.

What are the risks of surgery?

With all major operations there are some risks involved. There is a risk that you could be worse off if you suffer a significant complication such as cardiovascular problems (heart attack, stroke, thrombosis), infection, nerve and artery damage or a stiff painful artificial knee. There is a small risk (less than 1%) of dying having a knee joint replacement. 90% of patients having a total knee replacement have a good result at getting rid of pain and improving function. It is not a normal knee and some patients are disappointed that they can’t bend it as much as they would like. 5% of patients say they are worse following the operation largely due to one of the above complications of a major operation. Your surgeon will be happy to discuss the risk and benefits with you as the risks vary between individual patients.

Complications of the operation

This hospital employs a number of modern techniques to keep operative complications to a minimum. If you wish to know more about them your surgeon will be happy to explain. Despite using such techniques however, complications will occur. They are listed below and are accompanied by percentage figures, which indicate the number of patients per 100 who would be expected to develop the problem.

It is essential that you carefully read this list. When you sign your operation consent form it means that you are aware of the possible complications and the consequences of them.

Deep vein thrombosis

Blood clots can form in the veins of the legs. Minor clots of little importance can form in up to 50% of patients. In a smaller percentage of patients, the clots cause leg pain and swelling. This usually fully recovers, but 1% of patients are left with persistent leg swelling and discomfort.

Pulmonary Embolus

Some leg clots are large and can pass from the legs to the heart and lungs. This is called a pulmonary embolus and can result in sudden death. However, most patients who develop this condition while in hospital do survive after emergency treatment. This is the condition widely reported recently in the press and TV as occurring after long airplane journeys. Less than 1% of patients develop a pulmonary embolus. However, approximately four patients in 1000 die of pulmonary embolus.

Infection

Infections after knee replacements are of two types. The first is the so-called superficial infection, which occurs in 15% of cases. The wound becomes painful and inflamed after surgery but usually responds to antibiotics and a longer than average stay in hospital. Occasionally, an operation to clear the infection is needed.

Some superficial infections can involve the knee replacement itself – a deep infection. This usually results in loosening of the new joint, which then must be removed. A second joint replacement is then required – a revision procedure. Revision surgery is much more difficult than the original operation and has a higher complication rate.

Deep infections can also occur rarely, when bacteria infect the joint replacement from the patient’s own blood stream. This can occur after procedures such as passing a catheter into the bladder when a patient has difficulty passing urine after the operation. Overall the deep infection rate resulting in failure of the knee replacement is approximately 2%. It should be noted that both types of wound infection are more common in patients who are overweight or obese and in those with diabetes and general skin conditions such as psoriasis.

Most bacteria that cause infections are those, which live on normal skin. Hospital super bugs such as MRSA very rarely infect knee replacements.

Nerve and artery damage

The two main nerves supplying the leg (the femoral and sciatic) can be damaged, resulting in weakness and loss of feeling in the leg. Damage to the main artery to the leg requires emergency surgery at the time of the knee replacement, involving the vascular surgery team. Damage to nerves and arteries are fortunately very rare and occur in well under 1% of cases.

What sort of anaesthetic will be given to me?

You will be having either a spinal anaesthetic (in combination with sedation) or a general anaesthetic (GA) for the operation.

For more information, please ask for a copy of the leaflet

“You and Your Anaesthetic” (PIF 344).

You will be given an opportunity to discuss anaesthetic options and risks with your anaesthetist before your surgery.