Abscess nodule of the posterior compartment of the knee

A variety of masses in the knee must be considered in a differential diagnosis when swelling, pain, and a limitation of motion occur with no history of specific trauma. These lesions are most commonly related to the synovial lining of the joint capsule and the cruciate ligaments. The posterior compartment is an unusual location for solitary lesions of the knee joint. There have been few cases of abscess presenting as an intra-articular nodular mass. We report herein a case of a 15-year-old girl who had synovitis and an abscess nodule of the posterior compartment behind the posterior cruciate ligament in the knee joint. An arthroscopic synovectomy and mass excision along with antibiotic administration was curative in our case.