Medically reviewed on December 29, 2017
Knee replacement surgery — also known as knee arthroplasty (ARTH-row-plas-tee) — can help relieve pain and restore function in severely diseased knee joints. The procedure involves cutting away damaged bone and cartilage from your thighbone, shinbone and kneecap and replacing it with an artificial joint (prosthesis) made of metal alloys, high-grade plastics and polymers.
In determining whether a knee replacement is right for you, an orthopedic surgeon assesses your knee's range of motion, stability and strength. X-rays help determine the extent of damage.
Your doctor can choose from a variety of knee replacement prostheses and surgical techniques, considering your age, weight, activity level, knee size and shape, and overall health.
One of the most common reasons for knee replacement surgery is severe pain from joint damage caused by wear-and-tear arthritis (osteoarthritis). Osteoarthritis can erode the slick cartilage that helps your knee joint move smoothly. An artificial knee joint has metal alloy caps for your thighbone and shinbone, and high-density plastic to replace damaged cartilage.
Why it's done
The most common reason for knee replacement surgery is to relieve severe pain caused by osteoarthritis. People who need knee replacement surgery usually have problems walking, climbing stairs, and getting in and out of chairs. Some also have knee pain at rest.
Knee replacement surgery, like any surgery, carries risks. They include:
- Blood clots in the leg vein or lungs
- Heart attack
- Nerve damage
Signs of infection
Notify your doctor immediately if you notice:
- Fever greater than 100 F (37.8 C)
- Shaking chills
- Drainage from the surgical site
- Increasing redness, tenderness, swelling and pain in the knee
An infected knee replacement usually requires surgery to remove the artificial parts and antibiotics to kill the bacteria. After the infection is cleared, another surgery is performed to install a new knee.
Artificial knees can wear out
Another risk of knee replacement surgery is failure of the artificial joint. Daily use wears on even the strongest metal and plastic parts. Joint failure risk is higher if you stress the joint with high-impact activities or excessive weight.
How you prepare
Food and medications
Your doctor or anesthesiologist might advise you to stop taking certain medications and dietary supplements before your surgery. You'll likely be instructed not to eat anything after midnight the day of your surgery.
Prepare for your recovery
For several weeks after the procedure, you might need to use crutches or a walker, so arrange for them before your surgery. Make sure you have a ride home from the hospital and help with everyday tasks, such as cooking, bathing and doing laundry. If you live alone, your surgeon's staff or hospital discharge planner can suggest a temporary caretaker.
To make your home safer and easier to navigate during recovery, consider doing the following:
- Create a living space on one floor since climbing stairs can be difficult.
- Install safety bars or a secure handrail in your shower or bath.
- Secure stairway handrails.
- Get a stable chair with a firm seat cushion and back, and a footstool to elevate your leg.
- Arrange for a toilet-seat riser with arms if you have a low toilet.
- Get a stable bench or chair for your shower.
- Remove loose rugs and cords.
What you can expect
Before the procedure
Knee replacement surgery requires anesthesia. Your input and preference help the team decide whether to use general anesthesia, which makes you unconscious, or spinal anesthesia, which leaves you awake but unable to feel pain from your waist down.
You'll be given an intravenous antibiotic before, during and after the procedure to help prevent post-surgical infection. You might also be given a nerve block around your knee to numb it. The numbness wears off gradually after the procedure.
During the procedure
Your knee will be in a bent position to expose all surfaces of the joint. After making an incision about 6 to 10 inches (15 to 25 centimeters) long, your surgeon moves aside your kneecap and cuts away the damaged joint surfaces.
After preparing the joint surfaces, the surgeon attaches the pieces of the artificial joint. Before closing the incision, he or she bends and rotates your knee, testing it to ensure proper function. The surgery lasts about two hours.
After the procedure
You'll be taken to a recovery room for one to two hours. You'll then be moved to your hospital room, where you'll likely stay for a couple of days. Medications prescribed by your doctor should help control pain.
During the hospital stay, you'll be encouraged to move your foot and ankle, which increases blood flow to your leg muscles and helps prevent swelling and blood clots. You'll likely receive blood thinners and wear support hose or compression boots to further protect against swelling and clotting.
You'll be asked to do frequent breathing exercises and gradually increase your activity level.
The day after surgery, a physical therapist will show you how to exercise your new knee. After you leave the hospital, you'll continue physical therapy at home or at a center.
Do your exercises regularly, as instructed. For the best recovery, follow all of your care team's instructions concerning wound care, diet and exercise.
For most people, knee replacement provides pain relief, improved mobility and a better quality of life. And most knee replacements can be expected to last more than 15 years.
Three to six weeks after surgery, you generally can resume most daily activities, such as shopping and light housekeeping. Driving is also possible at around three weeks if you can bend your knee far enough to sit in a car, if you have enough muscle control to operate the brakes and accelerator, and if you're not still taking narcotic pain medications.
After recovery, you can engage in various low-impact activities, such as walking, swimming, golfing or biking. But you should avoid higher impact activities — such as jogging, skiing, tennis and sports that involve contact or jumping. Talk to your doctor about your limitations.
Artificial knee joints used in knee replacement surgery are typically made of metal and plastic. Metal alloy parts replace the damaged thighbone and shinbone. High-density plastic replaces cartilage on the shin and kneecap components.