Infrapatellar bursitis in children with juvenile idiopathic arthritis: a case series

Children with juvenile idiopathic arthritis (JIA) may infrequently present with localized anterior knee pain or swelling, in addition to generalize knee pain induced by JIA. We report five cases of deep infrapatellar bursitis in children with JIA. The clinical features, radiological findings, management, and outcome of five children with JIA and deep infrapatellar bursitis are reviewed. Three boys and two girls with a mean age of 9.8 years (range 6-14 years) were reviewed. Four children had persistent oligoarticular JIA, and one child had extended oligoarticular JIA. The presentation of deep infrapatellar bursitis was variable. In only one patient was the bursal swelling painful. Knee magnetic resonance imaging (MRI) was performed in four patients and demonstrated coexistent knee joint synovitis in three. Treatment included targeted corticosteroid injections into the deep infrapatellar bursa in two cases with complete resolution. One case was treated with corticosteroid injection by an outside health care provider with poor clinical response. Two cases are being treated with non-steroidal anti-inflammatory drugs and methotrexate. Deep infrapatellar bursitis can occur as an isolated finding or concurrently with knee joint synovitis in patients with JIA. Awareness of this entity is important because direct injection of the bursa may be needed for treatment, as the bursa does not communicate with the knee joint. Furthermore, when bursitis is suspected in JIA, MRI can be helpful to confirm the diagnosis, detect concurrent knee joint synovitis, and exclude other pathologies.