Arthritis is a group of conditions that cause damage to one or more joints. Your surgeon will recommend a unicompartmental knee replacement operation when the indications for such a procedure are met.

The most common type of arthritis is osteoarthritis, where there is gradual wear and tear of a joint. In some cases, this is the result of a previous injury, but usually, it occurs without a known cause. Arthritis eventually wears away the normal cartilage covering the surface of the joint causing the bone underneath to be damaged. This causes pain and stiffness in the joint, which can interfere with normal activities. If only part of your knee is damaged by arthritis, you can have a unicompartmental knee replacement instead of a total knee replacement.

A knee replacement is a surgical procedure that replaces the damaged parts of the knee with an artificial part, called a prosthesis.

The knee joint acts as a hinge between the bones of the leg and is made up of three parts.

● The major two joints are between the thigh bone of the upper leg (femur) and the shin bone of the lower leg (tibia).

● The smaller joint is between the kneecap (patella) and the upper leg (femur).

A smooth, tough tissue called cartilage covers the ends of the bones, allowing them to slide smoothly over each other.

During the operation, the damaged knee joint may be fully replaced or partially replaced if the damage is localised to a specific compartment with a metal shell on the end of the thigh bone and a metal and plastic spacer on the upper end of the shin bone. The surgery takes approximately 60 to 90 minutes to complete.

The goal of any knee replacement is to relieve pain, improve quality of life, and maintain or improve knee function with the correct prosthesis for the observed pathology.

The most common reason for a knee replacement is deterioration of the joints due to osteoarthritis of the knee.

Other possible causes include other forms of arthritis or knee injury.

Total Knee surgery (arthroplasty) is usually necessary when all the knee joint surfaces are damaged; Partial Knee Replacement (when only a part of the joint is damaged with reduced mobility and constant pain, even while resting) and other forms of treatment have not been able to relieve the pain.

Knee prostheses are designed to last for at least 15 to 20 years, especially if the knee that has been operated on, is cared for and not put under too much strain.

The goal is to achieve the best functional and pain-free joint without a deformity.

Simple painkillers such as paracetamol and anti-inflammatory painkillers such as ibuprofen can help control the pain of arthritis. Supplements to your diet, such as fish oil and glucosamine, may also help to relieve your symptoms. You should check with your doctor before you take supplements.

Using a walking stick on the opposite side of the affected knee may make walking easier. Wearing elasticated support on your knee may provide added support. Regular moderate exercise can help to reduce stiffness in your knee. Physiotherapy may help to strengthen weak muscles. A steroid injection may reduce pain in your knee joint and may sometimes reduce pain and stiffness for several months. You may have side-effects if you have injections too often.

An operation called a tibial osteotomy changes the shape of your leg and can take the load off the worn part of your knee. All of these measures become less effective if your arthritis worsens. This is when your surgeon may recommend a knee replacement.

Arthritis of the knee usually, though not always, worsens over time. Arthritis is not life-threatening in itself, but it can be disabling. Symptoms of arthritis can worsen, particularly when the weather is cold.

A variety of anaesthetic techniques are possible. Your anaesthetist will discuss the options with you and recommend the best form of anaesthesia for you. You may also have injections of local anaesthetic to reduce the pain after surgery. You may be given antibiotics during the operation to reduce the risk of infection. The surgical incision is on the front of your knee. The final decision, taken in theatre, will determine whether your knee is suitable for a unicompartmental replacement. If there is damage to other parts of your knee, you may require a total knee replacement. Your surgeon will remove the damaged joint surfaces. These will then be replaced with an artificial knee joint made of metal, plastic or ceramic, or a combination of these materials.

The knee replacement is attached to the bone, using acrylic cement or special coatings on the replacement pieces that bond directly to the bone. At the end of the operation, the skin is closed with clips.

After the surgery you may be given pain medication by injection or by mouth, an antibiotic to prevent infection, medicine and compression stockings to prevent blood clots in the legs.

You will be encouraged to start moving your feet and ankles immediately after surgery. It is common to begin physiotherapy, which is an important part of the recovery process, one day after surgery, while you are still in the hospital.

Physiotherapy will involve exercises to improve range of motion (how far you can bend and straighten your knee) and to strengthen your leg muscles. It is important to follow the physiotherapist’s advice to avoid complications of your surgery.

Your length of stay in the hospital varies from person to person, but your stay in hospital can be between 4 to 10 days during which time a physiotherapist will work with you and develop an exercise and rehabilitation programme. It is important that you continue these exercises after you have been discharged.

Depending on your progress, it is possible to be discharged from hospital within 1 to 3 days.

It is important to advise your surgeon about all of the medication you take and to follow the advice given about taking your medication before and after the operation. In some instances you may need to discontinue some medicine, while you may need to change the way you are taking other medicine. If you are diabetic, it is very important that your condition is controlled around the time of your operation. Follow your surgeon’s advice about when to take your medication before your operation.

Do not be surprised if you feel very tired at first. You have had a major operation and muscles and tissues surrounding your new knee will take time to heal. If you have any concerns, contact your doctor.

You should be able to stop using your crutches within 3 to 6 weeks after surgery. However, it may take up to six months for pain and swelling to settle down.

Your new knee will continue to recover up to two years after your operation.

You can resume driving when you can bend your knee enough to get in and out of a car and control the car properly. This is usually around 3 to 6 weeks after your surgery, subject to the advice of your doctor.

Depending on your job, you can usually return to work 6 weeks after your operation.  

Even after you have recovered, it is best to avoid extreme movements or sports where there is a risk of injury to your knee.

If you smoke, stop smoking several weeks or more before the operation. This may reduce your chances of complications and improve your long-term health.

Try to maintain a healthy weight. You have a higher chance of developing complications if you are overweight.

Regular exercise should help to prepare you for the operation, help with your recovery and improve your long-term health. Before you begin exercising, ask a member of the healthcare team or your GP for advice.