The knee consists of three separate parts, the patella-femoral joint (knee cap joint), the medial (inner) and the lateral tibio-femoral (outer) joint. There are also several ligaments, which help stabilise the knee, including the medial and lateral collateral ligaments and the cruciate ligaments.

In knee arthritis the bearing surfaces (articular cartilage) between the parts of the knee wears out. This results in friction within the joint, with a loss of the normal gliding action between the parts of the knee. This can cause stiffness in the joint and pain. When the arthritis becomes severe the two ends of the bone rub against each other and can cause a ‘grating’ sensation.

A knee replacement is an artificial joint made from a combination of metals and plastic. It consists of a metal cap that fits onto the end of your thigh bone (femur), a plastic bearing which sits on top of a metal plate attached to your shin bone (tibia). Sometimes the kneecap (patella) is replaced with a plastic button.

A knee replacement is predominantly used to treat moderate to severe arthritis. This can be from ‘wear and tear’ arthritis (osteoarthritis) or other types of arthritis such as rheumatoid arthritis.

There are two main types of knee replacement. A partial knee replacement is undertaken when arthritis is confined to one area of the knee, such as the medial compartment (inner knee chamber). A total knee replacement is undertaken when the arthritis affects several areas of the knee joint.

Knee replacement surgery is a major procedure so it is important to discuss the risks as well as the benefits when you come to your appointment.

Before you are scheduled for surgery you will be seen in the pre-operative assessment clinic. Here you will be seen by a nurse, who will ensure you are medically fit for the operation and arrange any necessary blood tests / investigations.

The surgery is usually done under a spinal anaesthetic. This is an injection into your back, which temporarily causes your legs to go numb, so you do not feel any pain during the operation. Sometimes the anaesthetist will give you medication to make you sleepy.

The surgery is carried out with a tourniquet (a tight band at the top of your thigh) to prevent any bleeding. The worn bearing surfaces are removed through a scar in the middle of the knee. These are replaced with two metal bearing surfaces separated by a plastic spacer. The wound is closed with stitches and covered with bandages.

Immediately after your surgery the aim is to reduce swelling, control any pain and restore movement back to the knee. Ice and strong painkillers are used to help achieve this. The physiotherapy team and nursing staff will look after you on the ward to help get you back up and mobile.

The initial recovery in hospital takes a few days. This is to help you get better from the operation, help control any pain and start exercising your knee.

When at home you will be given an exercise programme to follow and will be reviewed by the physiotherapists in the outpatient department. The sutures will be removed at two weeks and the wound checked for full healing. It takes several weeks to months to restore function to the knee and to realise the benefits of the surgery.