Periprosthetic joint infection (PJI) is a serious complication following total knee replacement surgery, occurring when bacteria colonize the tissues around the artificial joint. This infection is difficult to treat because the bacteria can form a protective layer called a biofilm on the implant’s surface, making them highly resistant to antibiotics and the body’s immune defenses. Treatment often requires complex, multi-stage surgeries to remove the infected components, a process that is costly and significantly delays recovery. A proactive, multi-phase prevention strategy is the most effective approach for patients.
Preventing Infection Before Surgery
Optimizing your overall health status before the operation is the first line of defense against infection. Managing chronic conditions, particularly diabetes, is essential, as high blood sugar levels impair the immune system and slow wound healing. Patients should aim for an optimal hemoglobin A1c level, typically below 7.5%, well in advance of the surgery date to reduce infection risk. Similarly, a body mass index (BMI) over 40 is a known risk factor, and a supervised weight-loss program is often required, as excess body fat can increase surgical time and compromise blood flow to the wound.
Quitting smoking is necessary, ideally at least four weeks before the procedure, because nicotine restricts blood vessels and limits the oxygen and nutrients needed for wound healing. Any active infection elsewhere in the body must be cleared before the knee replacement, including mandatory dental clearance. Bacteria from untreated dental decay or gum disease can enter the bloodstream and travel to the new joint.
Your surgeon will prescribe a specific skin preparation protocol to reduce the bacterial load on your skin. This often involves showering with an antiseptic soap, such as a chlorhexidine wash, for several days leading up to the surgery. Nasal decolonization with an antibiotic ointment, such as mupirocin, may also be required if you screen positive for Staphylococcus aureus colonization. Following these personalized instructions minimizes the risk of introducing skin bacteria into the surgical site during the operation.
Critical Care During Initial Recovery
The immediate post-operative period requires strict adherence to wound management protocols, as the surgical incision is the most common entry point for bacteria. Surgeons typically cover the wound with a specialized, sometimes waterproof, dressing that should remain intact for a specific period, often between seven and fourteen days. The patient or a trained caregiver must practice rigorous hand hygiene, washing hands thoroughly before and after any interaction with the dressing or the surgical area.
Monitor the wound for signs of persistent or excessive drainage, as this can provide a pathway for bacteria to enter the joint space. While a small amount of clear or pink-tinged fluid is normal for the first few days, contact your surgeon immediately if the dressing becomes saturated or if drainage continues beyond 72 hours. If a drain tube is present, follow precise instructions for emptying and measuring the fluid, which prevents the build-up of fluid that could become a bacterial culture medium.
Patients must avoid submerging the knee in a bathtub, pool, or hot tub until the surgical wound is completely healed and approved by the surgeon, which may take four to six weeks. If showering is permitted, the incision must be kept clean and dry, often by covering it with a waterproof shield or plastic wrap until staples or sutures are removed. This acute phase also requires strict compliance with the prescribed course of post-operative antibiotics to eliminate any bacteria introduced during or immediately after the procedure.
Recognizing Signs and Maintaining Long-Term Protection
Vigilance for infection must continue long after the incision has healed, as bacteria can settle on the implant years later through a process called hematogenous seeding. Acute periprosthetic joint infection (PJI) typically manifests within the first few weeks or months after surgery, presenting with classic inflammatory signs. These symptoms include increased warmth and redness around the joint, persistent or worsening pain, and purulent (pus-like) drainage from the wound. A fever or chills may accompany the acute infection, signaling a systemic response to the bacteria.
Chronic or late-onset PJI can occur years after the replacement, often presenting more subtly. The main symptom is usually persistent joint pain that may worsen over time and is not relieved by rest or standard pain medication. Other signs can include unexplained joint stiffness, swelling that does not respond to elevation or icing, or the development of a sinus tract, which is a small opening in the skin leading down to the infected implant. Prompt recognition and reporting of these symptoms is paramount, as delayed treatment necessitates more aggressive and complex surgical intervention.
Long-term protection requires prophylactic antibiotics for future invasive medical or dental procedures. These procedures, such as a tooth extraction, root canal, or certain urological or gastrointestinal scopes, can temporarily release bacteria into the bloodstream (bacteremia). For a minimum of two years post-surgery, and often for a lifetime in patients with increased risk factors like diabetes or a weakened immune system, antibiotics are taken one hour before the procedure. Informing all healthcare providers about the knee replacement is necessary to ensure this protective measure is always taken before any procedure that could potentially introduce bacteria into the bloodstream and seed the artificial joint.