Last reviewed: September 29, 2026

It is uncommon. About 1 in 200 people develop an infection of the new joint within a year, and about 1 in 60 within 15 years.

Those figures come from about 130,000 knee replacements in Canada. They count only infections that needed another operation, so the true rate is slightly higher. Most infections appear in the first two years. A few appear many years later, sometimes when bacteria from an infection elsewhere in the body travel through the blood to the joint. The rate fell slightly over the 15 years studied.

Obesity has the strongest evidence as a risk factor. Diabetes, smoking, anemia, poor nutrition, rheumatoid or other inflammatory arthritis, and heart, kidney or liver disease are also linked to more infection, as is a previous infection in a joint. Men have more infections than women. Knee studies found more infection in younger people, but studies of hips and knees together are mixed on age.

A weakened immune system also raises the risk. In people with rheumatoid arthritis, steroid pills were linked to more infection, more so at higher doses. The different biologic drugs carried similar risks to one another. People with an organ transplant or sickle cell disease have had more infections in record studies. In one large study, HIV without AIDS did not lead to more redo operations, while AIDS did.

These are links from records, not proof of cause, and most of the evidence is rated low quality.

According to the American Academy of Orthopaedic Surgeons, antibiotics given at the time of surgery and chlorhexidine antiseptic wipes used on the skin before surgery lower the risk, on limited evidence. Across all kinds of surgery, shaving the skin with a razor was linked to more infections than clipping the hair or leaving it alone. This has not been studied in knee replacement specifically. Antibiotics mixed into the bone cement have not been shown to lower infection after a knee replacement. Whether improving weight, blood sugar or smoking before surgery lowers the risk is not yet clear.

When a knee replacement does become infected, it usually needs more surgery, and function and quality of life are often worse afterward.

In general:

  • Tell your surgeon about diabetes, a transplant, HIV, sickle cell disease, any past joint infection, or medicines that weaken the immune system.
  • Ask how your arthritis or transplant medicines will be handled around surgery.
  • Ask your surgeon before shaving your leg in the days before surgery.
  • A knee that becomes more painful, swollen, red or warm, or starts draining, needs to be seen promptly, even years after surgery.

Drafted with AI assistance from published sources, reviewed and edited by Babak Sheikh, MD.

Sources:

This is general information about what published research shows. It is not medical advice and it is not about your situation. Reading it does not create a doctor-patient relationship with me. I am a retired orthopedic surgeon and I do not see patients. Talk with your own doctor before changing anything about your care. If something feels suddenly or seriously wrong, get medical care promptly rather than waiting.

This page is provided as is. I make no guarantee that it is accurate, complete or current, and medical evidence changes. Use of it is at your own risk.

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