Infection After Knee Replacement Surgery

Knee replacement surgery is a common procedure performed on more than 500,000 patients a year in the United States. While the majority of patients have no problems after surgery, there are risks of knee replacement that cause concern for anyone thinking of having this procedure. One of the most concerning complications associated with a knee replacement is an infection.

Infection after knee replacement surgery is rare. In the first 2 years after surgery, the chance of developing an infection is estimated at 1.5%. After 2 years, the chance of infection goes down to about 0.5%. While these numbers are exceedingly small, they are not zero, and people having a knee replacement need to know everything they can do to prevent this serious complication.

Antibiotics are a standard treatment for knee replacement infection.
Jose Luis Pelaez / Getty Images

Why Do Knee Replacement Infections Occur?

Knee replacements can become infected as a result of the initial surgical procedure, other infections in the body, or often for unknown reasons. We do know that some patients are more prone to developing infections of their knee replacement. Risks of developing an infection include:

Preventing Knee Replacement Infections

The foremost priority of knee replacements is to prevent infection from occurring at all. Some of the risks of developing an infection can be managed in a way to help lower the impact of these factors. For example, efforts to improve nutrition, reduce tobacco use, and discontinue medications that may make patients more susceptible to infection can all be done prior to undergoing knee replacement surgery. In the operating room, efforts are made to sterilize the skin and surgical area and minimize people coming in and out of the room. Intravenous antibiotics should be given within 1 hour from the start of surgery to ensure the lowest risk of infection.

Treatment of Knee Replacement Infections

Knee replacement infections are usually separated into categories of early versus late infections. Early infections occur within weeks or months of the surgery and are often treated with surgery to clean the infection, followed by antibiotic therapy targeted to the specific bacteria that is causing the infection. Multiple surgical procedures may be necessary, and antibiotics are usually continued for a minimum of 6 weeks.

Late infections are more difficult to treat and have often been present for weeks, months, or even years before the diagnosis of infection is made. The knee replacement implants may become loose if the infection has been present for a long time. In these cases, the implants often need to be removed and the infection treated. Most often, the infected knee replacement is removed, the infection is treated for a minimum of 6 weeks with antibiotics, and once the infection is cured, a new knee replacement is performed. This is a so-called two-stage revision knee replacement because two different surgeries are performed, one to remove the infected knee replacement, and another to put in a new knee replacement. In some cases, a one-stage revision, where the infected knee replacement is removed and a new one is put in during the same surgery can be performed. However, caution must be used, as if the infection is not adequately treated, then additional surgery will likely be necessary.

Success of Treatment

The success of treatment for knee replacement infections depends on a number of factors. Infections diagnosed early on tend to fare better than late infections. Infections of bacteria that are sensitive to more antibiotics are more easily treated than resistant infections. Overall, the success of the treatment is in the range of 70% to 90%. Some patients may require multiple surgical procedures, and in rare circumstances, some patients continue indefinitely on the antibiotic treatment known as chronic suppressive therapy. In these situations, it is felt that either the infection cannot be cured or the treatment would be too demanding for the patient, and the goal becomes to control the infection without curing it.

Once an infection is cured, and patients have a normally functioning knee replacement, they can resume all of their normal activities. While the treatment of a knee replacement infection is lengthy and demanding, orthopedic surgeons agree that with appropriate, aggressive treatment most patients can resume their normal active lifestyle. Unfortunately, even under the best circumstances, infection almost always leads to some loss of function of the knee replacement, even if the infection is eradicated from the replaced joint.

1 Source
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  1. Alamanda VK, Springer BD. Perioperative and Modifiable Risk Factors for Periprosthetic Joint Infections (PJI) and Recommended Guidelines. Curr Rev Musculoskelet Med. 2018;11(3):325-331. doi:10.1007/s12178-018-9494-z

Additional Reading

By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.