Background: Synovial lipomatosis is a rare, benign, intra-articular lipoma-like lesion characterized by villous proliferation of the synovium, most commonly affecting the knee joint. The usual presentation is long standing progressive swelling of the affected joint, with or without pain and restriction of movements. Histopathology is confirmatory. Case Report: We present the case of a 35- year old male patient with long standing history of swelling, short history of pain in the left knee joint. X-Ray and magnetic resonance imaging scans of the left knee showed the characteristic features of synovial lipomatosis with chronic synovitis. The patient underwent diagnostic arthroscopy with lavage of left knee joint. Histopathological study confirmed synovial lipomatosis with chronic synovitis. Conclusion: Synovial lipomatosis is a rare, benign, intra-articular lipoma-like lesion. Although rare, clinically it should be considered as an important differential in evaluating neoplastic and non- neoplastic conditions of the knee joint.