Knee replacement surgery is one of the treatment options for a knee joint that osteoarthritis has damaged. Osteoarthritis develops due to a breakdown of joint cartilage and the underlying bone.

A doctor may recommend surgery if other treatments, such as medicine and physical therapy, have not provided relief from pain and stiffness.

During the procedure, a surgeon will remove the damaged cartilage and bone before implanting an artificial joint comprising metal, plastic, and other synthetic materials.

According to the American Academy of Orthopaedic Surgeons (AAOS), over 90 percent of people who have a total knee replacement will have significantly less pain after the operation and a greater ability to move around and carry out daily tasks.

As with any surgical procedure, knee replacement surgery carries risks. These risks range from infection and pain to blood clots.

However, the AAOS point out that more than 600,000 procedures take place each year in the United States alone, with fewer than 2 percent resulting in serious complications.

Knee replacement surgery carries many different risks. Some result directly from the surgery, while others stem from the body’s reaction to the operation.

We discuss the possible risks in more detail below:


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If a person has severe knee pain due to osteoarthritis, a doctor may recommend knee surgery.

People who have knee replacement surgery require anesthesia to prevent them from feeling pain during the operation.

If a person opts for general anesthesia, they will be unconscious and will not wake up until the operation is over.

Alternatively, regional anesthesia only numbs the leg or lower body, and the person remains awake during surgery. They may receive sedatives to help them relax and enter light sleep.

General anesthesia can cause side effects, such as:

People are more likely to experience complications from general anesthesia if they already have another serious health condition, such as heart disease or lung problems.

Regional anesthesia causes fewer severe side effects than general anesthesia. It is also less likely than general anesthesia to make people feel drowsy after surgery, and the risk of blood loss, clots, heart attack, or stroke is lower.

Side effects from regional anesthesia can include:

  • headaches
  • trouble urinating
  • allergic reactions
  • in rare cases, nerve injury from the needle that delivers the anesthesia into the body


Any opening in the skin can allow bacteria to enter, which could potentially lead to infection. The surgeon will take precautions to minimize this risk during surgery.

Once the individual returns home, they should keep an eye out for the following signs of infection:

  • redness
  • swelling
  • warmth
  • discharge from the surgical site
  • fever and chills

If an infection arises, a doctor will prescribe antibiotics to treat it.


Bleeding during and after surgery is normal. In rare cases, a person may lose too much blood during the procedure and need a transfusion.

Sometimes, after surgery, blood can pool under the skin and cause swelling. If that happens, another procedure may be necessary to release the blood.

Blood clots

Blood clots are one of the most significant risks of knee replacement surgery. If surgery damages a blood vessel or the person does not move for several days after the procedure, blood flow can slow, and a blood clot may form.

A blood clot in one of the deep veins in the legs is called deep vein thrombosis (DVT). If the clot breaks free, it can travel to the lungs and block the flow of blood. This blockage is called pulmonary embolism, and it can be life-threatening.

Moving the legs and wearing compression devices after surgery can help prevent clots from forming.

Pain and swelling

Pain and swelling are common after surgery, but the severity of these symptoms will vary from person to person.

Doctors usually prescribe pain relievers to help manage any discomfort following surgery. This prescription is typically only valid for a short period, but, if the pain continues for a few months after surgery, the doctor may prescribe other treatments.

There may be swelling in the knee, ankle, and foot after surgery. Icing the area and doing light exercise can help lessen swelling.

Breathing problems

Some people have difficulty trying to breathe deeply straight after surgery, especially if they had general anesthesia.

If insufficient air reaches the lungs, mucus can build up inside them, and this can lead to pneumonia.

A healthcare professional will help the person take deep breaths to get the lungs working correctly again.

Nerve and artery damage

In rare cases, the surgeon may accidentally cut a nerve or blood vessel that runs close to the knee.

If this happens, a second surgical procedure might be necessary to repair the damage. A cut nerve can cause a loss of feeling or movement in the affected area, and this can sometimes be permanent.

Allergic reaction

Occasionally, people can have an allergic reaction to the metal components in knee implants. In some people with metal allergies, implant parts trigger a response that produces a range of symptoms, including swelling, a rash, and blisters.

In rare cases, allergic reactions can cause body-wide symptoms, such as weakness, diarrhea, headaches, and a loss of function in the implant area.

Individuals who have had skin reactions to metal jewelry in the past should check with their doctor whether a test for metal allergies is necessary before surgery.

Implant failure

Joint replacement technology has improved a lot over the years, but it is not perfect.

A new joint can loosen, wear out, or lose its stability.

If the joint fails, the person is likely to experience continued pain and stiffness after the surgery. They may need another procedure to replace it.

The best way to ensure a positive outcome is to follow the surgeon’s instructions. The individual should also make sure that they have asked any questions that they have regarding caring for their new knee.

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While rest is important, the person should start walking as soon as the doctor advises, to ensure good circulation.

The following tips should help prevent or reduce common knee replacement complications:

Take it slow: Doctors often encourage people to start using the new knee as soon as possible after surgery. However, it is vital not to overdo it. It can take 3 to 6 weeks before a person can return to some of their normal activities, including climbing stairs and driving.

Exercise: It is essential to get out of bed and move around. Doing the exercises that the doctor recommends will help a person regain movement in their knee. Staying active will also lower the risk of blood clots.

Use ice: Wrapping an icepack in a soft cloth and holding it on the knee can bring down swelling and reduce pain in the first few days after surgery. Propping the knee up on a couple of pillows can also help with swelling.

Pain relief: The surgeon will prescribe medication to relieve any pain following surgery. Managing pain can help the person stay active, which will speed up recovery.

Compression devices: The doctor will usually recommend wearing compression stockings or a boot-like device that continually applies pressure to the leg. These devices prevent blood from pooling in the legs and forming a blood clot.

Clean the wound: The surgeon will give instructions on how to care for the wound. Keeping the area clean can help prevent infection.

Before deciding on knee replacement surgery, people may wish to consider other noninvasive treatments that can relieve osteoarthritis pain and stiffness.

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For some people, using a stick or a walker might be a better option than surgery.

These treatments include:

  • specific devices, such as a cane, or a walker
  • exercise and physical therapy
  • pain relievers, such as acetaminophen (Tylenol), or nonsteroidal anti-inflammatory drugs, which include ibuprofen (Motrin), naproxen (Naprosyn), and celecoxib (Celebrex)
  • steroid injections into the knee
  • weight loss, if necessary

Maintaining a healthy weight and exercising regularly can help stop osteoarthritis from developing.

To ensure the best possible outcome from the surgery and reduce the risk of complications, people should find out as much information as they can before the surgery.

Questions to ask the doctor include:

  • What kind of outcome can I expect? How will knee replacement surgery help me?
  • Do I have any options other than surgery to relieve pain and stiffness?
  • What can I do in preparation for surgery to improve the likelihood of success?
  • What are the possible risks of having knee replacement surgery?
  • What can I do to lower the risk of complications?
  • What are the signs that I have a complication?
  • Under what circumstances should I call you?

Knee replacement surgery is a relatively standard procedure that improves mobility and quality of life for many people.

Fewer than 2 in every 100 people will experience a severe complication following knee replacement surgery, and this will usually relate to an existing health condition. It is best to discuss all treatment options with a doctor before deciding on surgery.