Knee washout is an urgent arthroscopic or open procedure to wash out an infected or contaminated knee joint. It is performed for septic arthritis, infected knee replacement (DAIR), and penetrating injuries to the knee joint.
Arthroscopic: the knee is accessed through standard portals. The joint is thoroughly irrigated with several litres of saline while infected tissue and debris are removed. Open: a larger incision allows direct access for more thorough debridement. For infected knee replacements, the polyethylene liner is exchanged and the entire joint is debrided. Multiple washouts may be needed. The procedure takes 30–90 minutes.
Knee washout is an emergency for septic arthritis to prevent cartilage destruction. For infected knee replacements, DAIR (debridement, antibiotics, implant retention) within a few days of symptom onset gives the best chance of retaining the prosthesis.
Needle aspiration may be performed diagnostically or as temporary treatment. However, established septic arthritis requires surgical washout — antibiotics alone are insufficient.
Joint aspiration for urgent microbiology. Blood tests including CRP, ESR, white cell count. This is an emergency procedure.
Clearance of infection, preservation of the joint surface (native or prosthetic). For native septic arthritis treated promptly, outcomes are generally good. For prosthetic infection, DAIR success is approximately 50–70%.
May require repeat washout or further surgery.
Post-infectious arthrofibrosis.
Intravenous then oral for weeks to months.
If septic arthritis is treated late, irreversible cartilage damage may occur.
If prosthetic infection cannot be cleared with DAIR.
Bone infection.
Systemic spread of infection.
General or spinal anaesthesia. Emergency procedure.
Intravenous antibiotics for two to six weeks. PICC line for outpatient IV therapy. Regular blood tests. Physiotherapy once infection is controlled. Full recovery depends on the extent of joint damage.
Regular blood tests. Clinical review at two weeks, six weeks, and three months. Long-term monitoring.
Septic arthritis can occur from bloodstream spread (haematogenous), direct inoculation (injury, injection), or spread from adjacent infection. Prosthetic joints are particularly susceptible because bacteria adhere to implant surfaces.