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What is a knee replacement surgery?
Knee replacement is a surgical procedure to resurface a knee damaged by arthritis. Metal and plastic implants are used to cap the ends of the bones that form the knee joint. This surgery may be considered for someone who has severe arthritis or a severe knee injury.
The goal of knee replacement surgery is to resurface the parts of the knee joint that have been damaged. It also relieves knee pain that cannot be controlled by other treatments.
Anatomy of the knee
Joints are the areas where two or more bones meet. Most joints are mobile, allowing the bones to move. The knee is two long leg bones held together by muscles, ligaments, and tendons. Each bone end is covered with a layer of articular cartilage that reduces joint friction, and absorbs the load of walking or weight-bearing.
There are two groups of muscles involved in the knee, including the quadriceps muscles (located on the front of the thighs), which straighten the leg at the knee, and the hamstring muscles (located on the back of the thighs), which bend the leg at the knee.
Tendons are elastic bands of connective tissue that connect muscles to bones. Ligaments are strong cords of tissue that connect bone to bone. Ligaments of the knee provide support and stability for the joint.
Reasons for the procedure
Knee replacement surgery is a treatment for pain and disability of the knee. The most common condition that results in the need for knee replacement surgery is osteoarthritis.
Osteoarthritis is characterized by the breakdown of joint cartilage. Damage to the articular cartilage and bones limits movement and causes pain. People with severe degenerative joint disease may be unable to do normal activities due to pain. Other forms of arthritis, fractures, torn cartilage, or torn ligaments may lead to irreversible damage or degeneration of the knee.
Some non-surgical treatments for degenerative joint disease may include:
- Anti-inflammatory medications
- Glucosamine and chondroitin sulfate
- Pain medications
- Limiting painful activities
- Assistive devices for walking (such as a cane)
- Physical therapy
- Cortisone injections into the knee joint
- Viscosupplementation injections (to add lubrication into the joint to make the joint less painful to move)
- Weight loss (for overweight/obese persons)
Risks of the procedure
As with any surgical procedure, complications can occur. Some possible complications may include:
- Blood clots in the legs or lungs
- Loosening or wearing out of the prosthesis
- Nerve or blood vessel injury
- Continued knee pain or stiffness despite the knee replacement
- Medical complications like heart attack or stroke
- The replaced knee joint may over time (usually 15 to 20 years) may have to be replaced
Be sure to discuss any concerns with your doctor prior to the procedure
Before the procedure
- Your doctor will explain the procedure to you and offer you the opportunity to ask questions. You will then be asked to sign a consent form that gives your surgeon permission to perform the procedure. Read the form carefully and ask questions if something is unclear.
- Your doctor may request a complete physical examination to ensure you are in good health before undergoing the procedure and may order blood tests or other diagnostic tests.
- Notify your doctor if you are sensitive to or are allergic to any medications, latex, tape, metal, and/or anesthetic agents (local and general).
- Notify your doctor of all medications (prescribed and over-the-counter) and herbal supplements that you are taking.
- Notify your doctor if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting. It may be necessary for you to stop these medications before the procedure.
- If you are pregnant or suspect that you are pregnant, you should notify your doctor.
- You will be asked to fast for eight hours before the procedure – generally nothing to eat or drink after midnight, the night before your surgery.
- You may receive a sedative before to the procedure to help you relax.
- You may meet with a physical therapist prior to your surgery to discuss rehabilitation.
- Arrange for someone to help around the house for a week or two after you are discharged from the hospital.
- Based on your medical condition, your doctor may request other specific preparation.
During the procedure
Knee replacement requires a short stay (usually one night) in a hospital. Procedures may vary depending on your condition and your doctor’s practices.
Knee replacement surgery is most often performed while you are asleep under anesthesia. Your anesthesiologist will discuss this with you in advance.
Generally, knee replacement surgery follows this process:
- You will be asked to remove clothing and will be given a gown to wear.
- An intravenous (IV) line may be started in your arm or hand.
- You will be positioned on the operating table.
- A urinary catheter may be inserted.
- If there is excessive hair at the surgical site, it may be clipped off.
- The anesthesiologist will continuously monitor your heart rate, blood pressure, breathing, and blood oxygen level during the surgery.
- The skin over the surgical site will be cleansed with an antiseptic solution.
- The doctor will make an incision in the knee area.
- The doctor will remove the damaged surfaces of the knee joint and resurface the knee joint with the prosthesis. The knee prosthesis is made up of metal and plastic. The most common type of artificial knee prosthesis is a cemented prosthesis. A cemented prosthesis attaches to the bone with surgical cement. An uncemented prosthesis attaches to the bone with a porous surface onto which the bone grows to attach to the prosthesis. Sometimes, a combination of the 2 types are used to replace the knee.
- The incision will be closed with stitches or surgical staples.
- A sterile bandage or dressing will be applied.
After the procedure
In the hospital
After the surgery you will be taken to the recovery room for observation. Once your blood pressure, pulse, and breathing are stable and you are alert, you will be taken to your hospital room. Knee replacement surgery usually requires an in-hospital stay of one night.
It is important to begin moving the new joint right after surgery. A physical therapist will meet with you soon after your surgery and plan an exercise program for you. Your pain will be controlled with medication so that you can participate in the exercise. You will be given an exercise plan to follow both in the hospital and after discharge.
You will be discharged home or to a rehabilitation center. In either case, your doctor will arrange for continuation of physical therapy until you regain muscle strength and good range of motion.
Once you are home, it is important to keep the surgical area clean and dry. Your doctor will give you specific bathing instructions. The stitches or surgical staples will be removed during a follow-up office visit.
To help reduce swelling, you will be asked to elevate your leg or apply ice to the knee.
Take a pain reliever for pain as recommended by your doctor. In most cases, resume your usual medicines. Be sure to take only recommended medications.
Notify your doctor of any of the following:
- Redness, swelling, bleeding, or other fluid drainage from the incision site
- Increased pain around the knee/incision site
You may resume your normal diet unless your doctor advises you differently.
You should walk frequently during the day, even if it is a short distance, to help prevent blood clots.
It is important that you avoid falls after your knee replacement surgery, because a fall can result in damage to the new joint. Your surgeon and your therapist may recommend an assistive device (cane or walker) to help you walk until your strength and balance improve.
Your surgeon and therapist will advise you on daily exercise, but it is important to fully extend (straighten) and deeply bend your knee frequently throughout the day, to prevent knee stiffness.
You should not drive until your doctor tells you to. Other activity restrictions may apply. Full recovery from the surgery may take several months.
Making certain modifications to your home may help you during your recovery. These modifications include, but are not limited to, the following:
- Proper handrails along all stairs
- Safety handrails in the shower or bath
- Shower bench or chair
- Raised toilet seat
- Long-handled sponge and shower hose
- Dressing stick
- Sock aid
- Long-handled shoe horn
- Reaching stick to grab objects
- Removing loose carpets and electrical cords that may cause you to trip
- Limiting stair-climbing
Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.
Daniel Valaik, MD, is a surgeon with Johns Hopkins Orthopaedic and Spine Surgery in the Greater Washington Area and an assistant professor of orthopaedic surgery at the Johns Hopkins University School of Medicine. He specializes in joint preservation surgeries of the hip and knee as well as total joint replacement, including total hip and total knee replacement surgeries.