Knee joint replacement
Knee joint replacement is surgery to replace a knee joint with a man-made (artificial) joint. The artificial joint is called a prosthesis.
See also: Unicompartmental knee arthroplasty
Total knee replacement; Knee arthroplasty; Knee replacement - total; Tricompartmental knee replacement; Subvastus knee replacement; Knee replacement - minimally invasive; Knee arthroplasty - minimally invasive
During knee joint replacement surgery, damaged cartilage and bone are removed from the knee joint. Man-made (artificial) pieces, called prostheses, are then placed in the knee. These pieces may be placed in up to three surfaces in the knee joint:
- Lower end of the thigh bone. This bone is called the femur. The replacement part is usually made of metal.
- Upper end of the shin bone--the large bone in your lower leg. This bone is called the tibia. The replacement part is usually made from metal and a strong plastic.
- Back side of your kneecap. Your kneecap is called the patella. The replacement part is usually made from a strong plastic.
You will not feel any pain during the surgery because you will have one of these two types of anesthesia:
- General anesthesia. This means you will be asleep and unable to feel pain.
- Regional (spinal or epidural) anesthesia. Medicine is put into your back to make you numb below your waist. You will also get medicine to make you sleepy. And you may get medicine that will make you forget about the procedure, even though you are not fully asleep.
After you receive anesthesia, your surgeon will make a cut over your knee to open it up. This cut is often 8 to 10 inches long. Then your surgeon will:
- Move your kneecap (patella) out of the way, then cut the ends of your thigh bone and shin (lower leg) bone to fit the replacement part.
- Cut the underside of your kneecap to prepare it for the new pieces that will be attached there.
- Fasten the two parts of the prosthesis to your bones. One part will be attached to the end of your thigh bone and the other part will be attached to your shin bone.
- Attach both parts to the underside of your kneecap. A special bone cement is used to attach these parts.
- Repair your muscles and tendons around the new joint and close the surgical cut.
The surgery usually takes around 2 hours.
Usually, artificial knees have both metal and plastic parts. Some surgeons now use different materials, including metal on metal, ceramic on ceramic, or ceramic on plastic.
Why the Procedure Is Performed
The most common reason to have a knee joint replaced is to relieve severe arthritis pain. Your doctor may recommend knee joint replacement if:
- You're having symptoms of knee arthritis, such as:
- You can't sleep through the night because of knee pain
- Your knee pain limits or keeps you from doing your normal activities, such as bathing, preparing meals, and household chores
- You can't walk and take care of yourself
- Your knee pain has not improved with other treatment
- You understand what surgery and recovery will be like
Knee joint replacement is usually done in people ages 60 and older. Younger people who have a knee joint replaced may put extra stress on the artificial knee and cause it to wear out early.
See also: Deciding to have knee or hip replacement
Risks of any surgery are:
- Blood clots that may travel from your legs to your lungs
- Breathing problems
- Heart attack or stroke during surgery
- Infection, including in the lungs, urinary tract, and chest
For more information about joint replacement, see also: Risks of hip and knee replacement.
Before the Procedure
Always tell your doctor or nurse what drugs you are taking, even drugs, supplements, or herbs you bought without a prescription.
During the 2 weeks before your surgery:
- Prepare your home.
- Two weeks before surgery you may be asked to stop taking drugs that make it harder for your blood to clot. These include aspirin, ibuprofen (Advil, Motrin), naproxen (Naprosyn, Aleve), and other drugs.
- You may also need to stop taking medicines that can make your body more likely to get an infection. These include methotrexate, Enbrel, or other medicines that suppress your immune system.
- Ask your doctor which drugs you should still take on the day of your surgery.
- If you have diabetes, heart disease, or other medical conditions, your surgeon will ask you to see the doctor who treats you for these conditions.
- Tell your doctor if you have been drinking a lot of alcohol, more than 1 or 2 drinks a day.
- If you smoke, you need to stop. Ask your doctor or nurse for help. Smoking will slow down wound and bone healing. Your recovery may not be as good if you keep smoking.
- Always let your doctor know about any cold, flu, fever, herpes breakout, or other illness you have before your surgery.
- You may want to visit a physical therapist to learn some exercises to do before surgery.
- Set up your home to make everyday tasks easier.
- Practice using a cane, walker, crutches, or a wheelchair correctly to:
- Get in and out of the shower
- Go up and down stairs
- Sit down to use the toilet and stand up after using the toilet
- Use the shower chair
See also: The night before your surgery - orthopedic
On the day of your surgery:
- You will usually be asked not to drink or eat anything for 6 to 12 hours before the procedure.
- Take the drugs your doctor told you to take with a small sip of water.
- Your doctor or nurse will tell you when to arrive at the hospital.
See also: Blood donation before surgery
After the Procedure
You will stay in the hospital for 3 to 5 days. During that time you will recover from your anesthesia and from the surgery itself. You will be asked to start moving and walking as soon as the first day after surgery.
Full recovery will take 3 months to a year.
Some people need a short stay in a rehabilitation center after they leave the hospital and before they go home. At a rehab center, you will learn how to safely do your daily activities on your own.
For more information, see also:
- Hip or knee replacement - in the hospital after
- Knee replacement discharge
The results of a total knee replacement are often excellent. The operation relieves pain for most people. Most people do not need help walking after they fully recover.
Most artificial knee joints last 10 to 15 years. Some last as long as 20 years before they loosen and need to be replaced again.
Crockarell JR, Guyton JL. Arthroplasty of the knee. In: Canale ST, Beatty JH, eds. Campbell's Operative Orthopaedics. 11th ed. Philadelphia, Pa: Mosby Elsevier; 2007:chap 6.
Jones CA, Beaupre LA, Johnston DW, Suarez-Almazor ME. Total joint arthroplasties: current concepts of patient outcomes after surgery. Rheum Dis Clin North Am. 2007; 33(1): 71-86.
Leopold SS. Minimally invasive total knee arthroplasty for osteoarthritis. N Engl J Med. 2009;360:1749-1758.
C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Dept of Orthopaedic Surgery. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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