Acute pseudoseptic arthritis after intraarticular sodium hyaluronan

A 70-year-old woman with a history of knee osteoarthritis was admitted for acute arthritis 9 days after a second intraarticular injection of sodium hyaluronan (Ostenil). The joint fluid was purulent, with no crystals, and laboratory tests showed marked inflammation, leading to antibiotic treatment for suspected septic arthritis. Incapacitating symptoms persisted, prompting surgical lavage of the knee, which failed to relieve the severe pain. The persistent symptoms and negative results of joint fluid and blood cultures led to discontinuation of the antibiotic therapy after 10 days. Antiinflammatory therapy relieved the symptoms, and the patient was discharged home 1 month after her admission. Nevertheless, the pain persisted, requiring rehabilitation therapy of the knee. Aseptic arthritis induced by repeated sodium hyaluronan injection is the most likely diagnosis. Physicians should be aware of this extremely severe complication.