Pseudoseptic arthritis as a complication of intra-articular infiltration of hyaluronic acid in a patient with rheumatoid arthritis

Pseudoseptic arthritis is a rare complication of hyaluronic acid (HA) injections that often is difficult to differentiate from septic arthritis. Patients present acute pain, swelling and joint effusion normally around 24 h after the second or third HA infiltration. We describe a female patient with seropositive rheumatoid arthritis and flare-ups of knee arthritis with pseudoseptic features in the past, who develops pseudoseptic arthritis of the knee following her first injection of hyaluronic acid.