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Knee Replacement Complications

Complications of knee replacement surgery can result from surgery or a faulty implant. A loss of knee motion and pain are common complications. More severe complications requiring revision surgery include joint replacement infection, unexpected bleeding into the knee joint and prosthetic loosening.

Last Modified: April 25, 2024
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Common Knee Replacement Complications

Pain is the most common complication after joint replacement. Total knee replacement restores function to the knee in 90% of cases, but complications can sometimes happen after knee replacement surgery.

Other common complications of knee surgery include:
  • Clicking or popping
  • Loosening
  • Nerve damage
  • Swelling and stiffness

Your age, health and activity level all contribute to the risk of complications after knee replacement surgery. If you continue to experience knee replacement problems two years after surgery (including pain) speak with your doctor to determine if there are any other issues.

Clicking or Popping

Clicking, grinding and popping sounds after surgery are common knee replacement side effects. “Most people also feel or hear some clicking of the metal and plastic with the knee bending or walking,” according to the American Academy of Orthopaedic Surgeons.

Tapping or clicking sounds usually begin several weeks after knee replacement surgery as swelling reduces and the range of motion improves. At the three-month mark, noises may occur more often with increased physical activity.


It’s normal for patients to experience some degree of pain up to six months after surgery. However, if pain persists six months after the procedure, it’s generally considered long-term or chronic.

Several studies have examined chronic pain frequency among total knee replacement patients. Findings suggest that approximately 20% of patients report this complication.

“It is also possible that the true prevalence of chronic pain after TKA [total knee arthroplasty] is even higher than estimated in research studies, as some patients may be reluctant to report that they have pain,” according to a 2018 article published in EFFORT Open Reviews.


TKA aims to restore knee movement, typically in those with osteoarthritis. Stiffness should resolve within six weeks after the operation. After three months post-op, patients should regain 90% of their knee motion.

A restricted range of motion may persist post-surgery if an individual had knee stiffness before TKA and the surgeon could not address the anatomical issues causing stiffness. In addition, lifestyle habits associated with stiffness can contribute to a limited range of motion after the procedure. Finally, specific surgical errors during TKA can also hinder knee function and result in postoperative knee stiffness.

Nerve Damage

Nerve damage can happen during surgery, but it usually goes away within six months. Symptoms of nerve damage include radiating pain, a tingling sensation in the leg and numbness in the leg or foot.

Surgeons must cut and stretch skin and muscle during surgery. The American Academy of Orthopaedic Surgeons says “pressure, stretching or cutting” can damage nerves in the leg or around the joint.

Knee surgery may involve special tourniquets to limit blood flow in the leg. This restriction may put pressure on nerves, resulting in damage.

Serious Knee Replacement Surgery Risks

As with any major surgery, severe but rare complications such as blood clots and infection are possible. Fewer than 2% of patients experience them. Complications may result from the knee surgery or the device itself, as with implant rejection.

Serious TKA complications include:
  • Allergic reaction
  • Blood clots
  • Heart attack
  • Hemorrhage
  • Infection
  • Stroke

Blood clot complications arise from deep vein thrombosis or a pulmonary embolism (when a clot travels to the lungs).

Common peroneal nerve (PN) palsy is a serious and functionally debilitating complication that can occur after TKA. Individuals with a valgus deformity have a higher risk of this complication.

Allergic Reaction to Bone Cement

Severe hypersensitivity reactions to acrylic bone cement and its additives are rare but serious. These complications may cause pain, swelling, dermatitis and loosening. As a preventative measure, some surgical centers now conduct an allergy panel before surgery to test for reactions in patients.

Nerve Block Complications

Nerve blocks are a widely used and relatively safe form of anesthesia given to patients before knee replacement. Complications of nerve blocks are uncommon but may affect surgical outcomes.

Some side effects include elevated blood sugar, rash, bleeding and itching or soreness at the injection site. Nerve blocks may also cause nerve damage if injected into the wrong place. In rare cases, nerve block complications are fatal.

Complications That May Require Knee Revision

Fractures, implant failure or infection are just three complications that may require a knee revision. A knee revision, or reoperation, is a surgery that replaces the prosthetic implants from the original surgery.

Those who have knee replacement surgery may require another prosthetic knee over time. A knee revision may be necessary if knee implants fail because of wear, loosening or other issues.

Complications that can lead to a revision include:
  • Fractures
  • Implant rejection
  • Infection
  • Instability and dislocation
  • Knee implant loosening
  • Misalignment and failure
  • Soft tissue problems

Studies have shown that frequent reasons for revision are infection, aseptic loosening and periprosthetic fracture. Periprosthetic fractures occur in the femur, tibia or patella.

Aseptic loosening refers to a prosthetic failure that is not the result of a mechanical issue. Instead, the loosening is associated with bone resorption or inflammatory response in the cells of the joint. 


While the risk of infection is low, it can be a devastating complication from knee replacement surgery. The metal and plastic implants may serve as a surface for bacteria to grow, and their location may make them inaccessible to antibiotics. As a result, infections can damage muscle or bone, weakening the implant.

Infection often requires surgery to remove the device and infected muscle or other tissue. Successful treatment depends on the bacteria, the infection duration and the patient’s health. In rare cases, infections may lead to amputation.

Soft Tissue Problems

Wound and skin healing complications and other soft tissue problems may occur after knee replacement. These complications can result in severe issues for patients.

Soft tissue coverage is crucial for prosthesis retention and healing. Failure to identify wound healing complications early can lead to necrosis (tissue death), infection and loss of the prosthesis.

Knee Implant Loosening

Loosening is one of the most common complications of total knee replacement surgery requiring revision. There are several causes for loosening; infection is a likely cause. Aseptic loosening is an inflammatory response resulting in bone loss and implant loosening when there’s no infection.

Younger age is associated with a higher risk of aseptic loosening. Other factors include age, sex, BMI, activity levels, consumption of alcohol and tobacco, and bone geometry and quality.

Faulty design, product defects, or wear and tear on implant parts can also cause loosening. For example, knee replacement lawsuits have claimed DePuy Attune implants loosened because the cement used to connect the device to bone failed.

Instability and Dislocation

A total knee replacement, or TKR, with instability occurs when the supporting soft tissues have failed or cannot function because of the component size and/or position. It is a common reason for revision surgery, but specialists say that identifying the causes of instability can make it possible to restore balance and stability for a successful outcome.

Misalignment and Failure

Components in an artificial knee must be precisely aligned to work. If they do not line up, they can wear out too soon, or the implant can fail without warning.

Symptoms of misalignment and failure include instability, pain and swelling. Other signs include reduced range of motion and heat around the joint. Patients almost always need revision surgery to fix misalignment problems.


Fractures after TKR are a rare complication that may require revision knee replacement. Fractures to the femur, tibia or patella may occur anytime, even years after surgery.

The risk factors associated with fracture include inflammatory conditions, age and osteoporosis. Additionally, long-term steroid use and certain neurological diseases such as Parkinson’s or epilepsy increase risk.

Implant Rejection

Knee implant rejection is extremely rare. Implant rejection or metal hypersensitivity happens when the metal in the implant triggers a reaction in the patient’s body. This issue can be an allergic reaction or an autoimmune response.

Unfortunately, testing for metal hypersensitivity to a metal joint replacement is complex. Specialists are still learning about this condition, so optimal treatment is unclear.

Long-Term Complications of Knee Replacement

TKR usually improves physical function and reduces pain, but pain is one of the most common long-term complications of knee replacement surgery. Around 20% of patients report chronic postoperative knee pain. Studies have associated this type of chronic pain with decreased function, increased inflammation and higher levels of depression.

Another long-term complication is knee stiffness related to heterotopic ossification. In HO, new bones form around the muscles, tendons, ligaments and cartilage. Fortunately, multiple treatments are available for HO, including anti-inflammatory drugs and physiotherapy.

If you begin to experience knee replacement problems ten years after surgery, you may be experiencing a loosening of the implant or some other complication. Be sure to follow up with your doctor for the care you need.

Please seek the advice of a medical professional before making health care decisions.