Surgical management of septic arthritis of the knee with a coexistent popliteal cyst.

We report a case of knee pyarthrosis in a 54-year-old woman with rheumatoid arthritis and a popliteal cyst. The onset of infection coincided with a cortisone injection. Initial management consisted of arthroscopic irrigation and debridement (I&D) on 2 consecutive occasions without resolution of the infection. Only after open excision of the popliteal cyst in conjunction with I&D of the knee joint proper did the infection resolve. This is the first reported case of a patient requiring excision of a popliteal cyst to clear pyarthrosis of the knee after failure of arthroscopic I&D. Consideration should be given to open debridement or drainage of popliteal cysts in patients who present with septic arthritis in the presence of a popliteal cyst. A treatment algorithm for managing this clinical scenario is presented.