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Risks of knee replacement surgery


There is a risk of complications with all surgeries. Understanding these risks and how they apply to you should be part of deciding whether to have surgery.

Proper care and planning before surgery may prevent these risks or make them less likely to occur. Choose a doctor and a hospital that provide high-quality care. Talk with your doctor long before your surgery about what you can do to prevent problems during and after surgery.

Risks that may occur with any surgery

  • Breathing problems after surgery. These are more common if you have had general anesthesia and a breathing tube.
  • Heart attack or stroke during or after surgery.
  • Infection in the knee, lungs (pneumonia), or urinary tract.
  • Poor wound healing. This is more likely for people who are not healthy before surgery, people who smoke or have diabetes, or people who take medicines that weaken the immune system.
  • Injuries to muscles, tendons, nerves, and blood vessels.
  • An allergic reaction to any of the medicines you receive is rare but may occur. Some of these reactions may be life threatening.
  • Falls in hospitals can be a major problem. The cause may be loose gowns, slippery floors, medicines that make you sleepy, pain, unfamiliar surroundings, feeling weak after surgery, or moving around with a lot of tubes attached to your body.
  • Blood clots that occur in the calf and can move to the lungs.
  • Fractures that can occur when the implants are being put in your knee.


It is normal to lose blood during knee-replacement surgery. Some people need to have a blood transfusion during surgery or their recovery in the hospital. You are less likely to need a transfusion if you are not anemic (have a low blood count) before surgery.

Much of the bleeding comes from the bone that has been cut. A hematoma (bruise) may occur if blood collects around the new knee joint or under the skin after surgery.

Blood clots

You are more likely to form a blood clot during and soon after knee-replacement surgery. Sitting or lying down for long periods of time during and after surgery will make your blood move more slowly through your body, and this increases your risk of a blood clot.

Two types of blood clots are:

  • Deep vein thrombosis (DVT) -- these are blood clots that may form in your leg veins after surgery.
  • Pulmonary embolism -- these are blood clots that may travel up to your lungs and cause serious breathing problems.

To lower your risk of blood clots, you:

  • May receive blood thinners before and after surgery.
  • Will wear compression stocking on your legs after surgery to improve blood flow.
  • Will be encouraged to get out of bed and walk in the halls to improve blood flow.

Possible problems with a new knee joint

These are some problems that may occur after your knee-replacement surgery:

  • Infection in your new knee. If this occurs, your new joint may need to be removed to clear the infection. This problem is more likely in people who have diabetes or a weakened immune system. After surgery, you will learn what you can do to prevent infections in your knee joint.
  • Loosening of your new knee joint over time. This can cause pain, and sometimes another surgery is needed to fix the problem.
  • Wear and tear of the moving parts of your knee joint over time. Small pieces may break off and damage the bone. This may require another operation to replace the moving parts and repair the bone.
  • Dislocation of the knee cap or patella. Wrong movement or falls can lead to dislocation of the knee cap. This may require a second operation to repair the injury.
  • Instability of the knee replacement. Your replacement may become lose due to injury. If so, you may need surgery to fix your new knee.
  • Stiffness. Inadequate rehabilitation or poor healing can lead a stiff knee replacement. This can give incomplete pain relief and discomfort with activities of daily living.
  • Fractures around the prosthesis. This can occur during or after surgery. This usually requires another operation to fix the fracture.
  • An allergic reaction to the metal parts in some artificial joints. This is very rare.

Other risks

Other problems from knee-replacement surgery can also occur, but these are rare. Three of these are:

  • Not enough pain relief. Knee-replacement surgery relieves the pain and stiffness of arthritis for most people. Some people may still have some symptoms of arthritis, though. Surgery usually provides enough relief of symptoms for most people.
  • A longer or shorter leg. Because bone is cut away and a new knee implant is inserted, your leg with the new knee joint may be longer or shorter than your other leg. This difference is usually about 1/4 of an inch. It rarely causes any problems or symptoms.
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Review Date: 8/9/2018

Reviewed By: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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