Case Studies

 Case 10.1 Septic arthritis

A 37-year-old woman developed a symmetrical polyarthritis. A test for rheumatoid factor was positive and erosive changes were seen on X-ray confirming a clinical diagnosis of RA. The arthritis followed an aggressive course with poor response to a variety of disease-modifying antirheumatic drugs and she became increasingly disabled due to severe destructive changes in the knees, wrists and shoulders. A moderate dose of prednisolone was introduced at the age of 42, with some symptomatic improvement in her joints and she was referred to an orthopaedic surgeon with a view to knee replacements. However, 1 month before her orthopaedic appointment she presented to the emergency department with a painful swollen right knee. On examination she was unwell, febrile (38°C) and had a hot, red right knee with a sizable effusion. 80ml of purulent synovial fluid was aspirated from the joint and microscopy of the fluid revealed numerous Gram-positive cocci. A diagnosis of septic arthritis was made on a background of severe RA and steroid therapy. She was treated with high-dose antibiotics and the joint was washed out via an arthroscope. Culture of blood and synovial fluid grew Staphylococcus aureus. She received 6 weeks antibiotic treatment in total together with vigorous physiotherapy. Her knee, however, was significantly worsened by the infection and she could no longer straighten the leg or walk more than a few yards. Joint replacement was deferred for 6 months to reduce the risk of infection in the prosthesis.