Localised Nodular Synovitis: an Uncommon Cause of Knee Pain

Localised nodular synovitis is a benign localised synovial proliferative tumour that occurs in the tendon sheath. This tumour rarely involves the large joints such as the knee. This report is of a patient with localised nodular synovitis at the infrapatellar region of the knee, who presented with chronic knee pain. Magnetic resonance imaging was performed and the diagnosis was confirmed histologically after excision of the tumour. There are many differential diagnoses for solitary lesion of the knee, and the clinical manifestations can be non-specific. Systematic imaging is an important part of making the diagnosis. Synovial lesion of the knee is an infrequent condition, and localised nodular synovitis is one of the rarer differential diagnoses, but it should be considered in cases of knee pain and solitary nodule in the knee.