Risks of Total Knee Replacement Surgery

Reviewed by Greg Jaroszynski MD, FRCSC | Last updated May 2026

Total knee replacement is a common and generally safe operation, but serious complications can occur and each patient's risk is different.

General Expectations

Most patients recover without a major complication.
Serious complications are uncommon, but they can occur.
The purpose of reviewing risk is not to create fear, but to make sure the decision for surgery is thoughtful and well informed.
Personal risk varies depending on age, medical history, general fitness, weight, diabetes control, smoking, previous blood clots, immune suppression, skin health, and the complexity of the knee.

Surgical and Implant-Related Risks

These are risks directly related to the operated knee, the incision, or the knee replacement components.

Infection
Bleeding, bruising, or wound healing problems
Stiffness or reduced range of motion
Persistent pain, swelling, or dissatisfaction with the result
Numbness around the incision, clicking, clunking, or other mechanical sensations
Instability or the feeling that the knee does not move naturally
Fracture around the knee replacement
Loosening, wear, or later need for revision surgery

Medical Risks

Total knee replacement is a major operation, so complications can also occur elsewhere in the body.

Blood clots in the leg veins or lungs
Heart rhythm problems or heart attack
Lung complications, such as pneumonia
Kidney or urinary problems
Stroke
Medication-related side effects
Confusion or delayed recovery, especially in medically fragile patients

Rare but Serious Complications

Deep infection requiring further surgery
Nerve or artery injury
Major blood clot travelling to the lungs
Permanent stiffness, weakness, instability, or chronic pain
Need for revision surgery
Death

Infection

Infection is one of the most serious risks after knee replacement. A superficial wound infection may sometimes be treated with antibiotics, but a deep infection around the prosthesis can require one or more further operations, prolonged antibiotics, and sometimes removal or exchange of the implants.

Large patient information sources estimate serious infection after total knee replacement at less than 2%, but the risk is higher in patients with certain medical conditions.

Blood Clots

Blood clots can form in the leg veins after surgery and can travel to the lungs. Modern prevention includes early walking, leg exercises, compression when appropriate, and blood-thinning medication when prescribed.

Venous thromboembolism has become less common than in the past, but it remains one of the important medical risks after hip and knee replacement.

Persistent Pain, Stiffness, or Dissatisfaction

Not every problem after knee replacement is immediately visible on x-rays. Some patients have stiffness, swelling, numbness, clicking, instability, or persistent pain despite apparently well-positioned components.

Recent literature reports that unfavorable long-term pain outcomes can occur in a meaningful minority of patients, and dissatisfaction after total knee replacement averages around 10% in modern systematic review data. Persistent or worsening pain should be assessed because infection, loosening, instability, fracture, spine disease, nerve pain, or other correctable causes may be present.

Putting Risk in Perspective

Complications are an inevitable reality of any surgical procedure. Fortunately, total knee replacement is a common and generally safe operation, and most patients recover without a major complication. The list of possible complications is long, but most of them are uncommon.

A review of systemic medical complications after joint replacement reported systemic complication rates of about 6.9% for knee replacement and mortality around 0.2%, with preoperative comorbidity being an important risk factor. These numbers are averages across studies and do not predict an individual patient's risk.