Summary

A 9-month-old girl presented with a swollen, erythematous and hot left elbow, which was tender on palpation. Physical examination was unremarkable except temperature of 38.4°C and restriction of elbow movement. Blood tests showed an elevated C reactive protein of 116 mg/L. Plain radiograph and ultrasound of the elbow showed no pathological findings. MRI revealed an intra-articular effusion and associated myositis, but did not demonstrate intra-articular synovitis. Arthroscopic lavage of the joint yielded purulent fluid and gross synovitis involving the entire joint. Streptococcus pneumoniae was isolated from the synovial fluid, although the patient had been immunised with Prevenar (pneumococcal vaccine). Postoperative empiric treatment with antibiotics for 6 weeks was started. Follow-up of 2 years revealed a healthy girl with a full range of motion of her elbow and no signs of complications. This case of septic arthritis emphasises the importance of the clinical presentation to determine the correct diagnosis and treatment modalities.