Knee replacement

A knee replacement (knee arthroplasty) swaps the worn surfaces of the knee joint for an artificial joint of metal and plastic. A total replacement covers both bone ends of the joint. A partial replacement, used when arthritis affects only one half of the knee, replaces only that side, with a smaller cut and usually quicker recovery.

Most knee replacements are done for osteoarthritis, in which the cartilage cushioning the bone ends wears away, so the bones rub together and cause pain and stiffness. Rheumatoid arthritis and arthritis after an injury can also be treated this way. It is considered when knee pain badly disturbs sleep, walking or daily life and other treatments have not worked. Younger people may wear the new joint out sooner.

You may attend a pre-admission clinic a few weeks before, for a blood test and a blood pressure check.

You have either a general anaesthetic, so you are asleep, or a spinal anaesthetic, which numbs you from the waist down while you stay awake. A total knee replacement goes like this:

1. A cut is made down the front of the knee and the kneecap is moved aside.
2. The worn ends of the thigh bone and shin bone are shaped.
3. Metal and plastic parts are fitted to the bone ends.
4. The kneecap is put back and the cut is closed with stitches or clips.
5. You wake in a recovery room with pain relief.

It usually takes 1 to 2 hours.

Physiotherapists help you stand and walk soon after the operation. Most people go home within a few days if there are no problems. The knee is sore, so you take painkillers regularly at first. Do the exercises you are given, as starting early helps strength and movement. Keep the leg raised to ease swelling, and wear compression stockings, usually for several weeks. People are usually advised to wait about 6 weeks before driving, not to kneel on the new knee until the surgeon agrees, and to avoid heavy household tasks for 3 months.

Get urgent advice for a fever, pus from the wound, a hot, red or more painful knee, or throbbing calf pain. Leg pain with chest pain or breathlessness needs emergency care.

Most people have no complications, and those that happen are usually minor and treatable, but this is a major operation. Risks include blood clots in the leg veins, which can travel to the lungs (stockings or blood-thinning medicines help prevent them), and wound infection, usually treated with antibiotics, though deep infection in the joint may need another operation. Damage to nerves, blood vessels or ligaments is not common. The knee may stay stiff, painful or unsteady.

Knee replacement relieves pain for most people and improves movement, and most no longer need help walking once fully recovered, which takes several months and sometimes up to a year. An artificial knee can wear out or loosen. Many last 15 years or more, and some about 25. A second operation (revision) can be done, though results are usually not as good as the first time. A check-up follows about 6 weeks after surgery, with later check-ups of the joint.