Knee replacement, also known as knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability. It is most commonly performed for osteoarthritis, and also for other knee diseases such as rheumatoid arthritis and psoriatic arthritis.
Your knee joint is made up by the ends of your thigh bone (femur) and shin bone (tibia). These normally glide over each other easily because they are covered by smooth cartilage. If your cartilage is damaged by injury or worn away by, for example, it can make your joint painful and stiff. A new knee joint usually improves mobility and reduces pain, although your new knee will not be able to bend quite as far as a normal knee joint. Depending on the condition of your knee joint, you may have part or all of your knee joint replaced. A total knee replacement is more common. Artificial knee parts can be made of metal and/or plastic and a knee replacement can last for up to 20 years.
Surgery is usually recommended only if non-surgical treatments, such as physiotherapy and exercise, taking medicines or using physical aids like a walking stick, no longer help to reduce pain or improve mobility. Alternative surgical procedures include arthroscopy (if the arthritis isn’t too severe) or osteotomy (where the leg bones are cut and re-set). You may have already had these procedures before your knee replacement.
Your surgeon will explain how to prepare for your operation. For example if you smoke you will be asked to stop, as smoking increases your risk of getting a chest and wound infection, which can slow your recovery. The operation usually requires a hospital stay of about five days and it's done under general anaesthesia. This means you will be asleep during the operation. Alternatively you may prefer to have the surgery under spinal or epidural anaesthesia. This completely blocks feeling from your waist down and you will stay awake during the operation. If you’re having a general anaesthetic, you will be asked to follow fasting instructions. This means not eating or drinking, typically for about six hours before a general anaesthetic. However, it’s important to follow your anaesthetist’s advice. At the hospital, your nurse may check your heart rate and blood pressure, and test your urine. Your surgeon will discuss with you what will happen before, during and after your procedure, and any pain you might have. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead, which you may be asked to do by signing a consent form. You may be asked to wear a compression stocking on the unaffected leg to help prevent blood clots forming in your veins (deep vein thrombosis, DVT). You may need to have an injection of an anticlotting medicine called heparin as well as, or instead of, stockings.
A knee replacement usually takes up to two hours. Your surgeon will make a single cut (10 to 30cm long) down the front of your knee. He or she will move your kneecap to one side to reach the knee joint. Your surgeon will remove the worn or damaged surfaces from both the end of your thigh bone and the top of your shin bone. He or she will usually remove your anterior cruciate ligament and may remove your posterior cruciate ligament. For support, your surgeon won’t remove your collateral ligaments. He or she will shape the surfaces of your thigh and shin bones to fit the artificial knee joint and then fit the new joint over both bones. Sometimes the back of your kneecap is replaced with a plastic part. This is called patellar resurfacing. After your surgeon has fitted the new joint, he or she will close your wound with stitches or clips and cover with a dressing. Your surgeon will tightly bandage your knee to help minimise swelling.
You will need to rest until the effects of the anaesthetic have passed. You may not be able to feel or move your legs for several hours after an epidural anaesthetic. You may need pain relief to help with any discomfort as the anaesthetic wears off. For the first day or so, you may have an intermittent compression pump attached to special pads on your lower legs. By inflating the pads, the pump encourages healthy blood flow and helps to prevent DVT. You may also have a compression stocking on your unaffected leg. This helps to maintain circulation. A physiotherapist (a specialist in movement and mobility) will usually guide you daily through exercises to help your recovery. You will be in hospital until you can walk safely with the aid of sticks or crutches. When you’re ready to go home, you will need to arrange for someone to drive you. Your nurse will give you some advice about caring for your knee and a date for a follow-up appointment before you go home. The length of time your dissolvable stitches will take to disappear depends on what type you have. However, for this procedure they should usually disappear in about six weeks. Non-dissolvable stitches and clips are removed 10 to 14 days after surgery.