Lipoma arborescens is an infrequent cause of chronic pain and swelling of the knee joint, and it is a slow-growing pseudotumoral lesion. Only very few cases are reported in the literature, it is most commonly seen in the knee joint, but involvement in other joints such as the wrist, shoulder, and elbow have also been reported. We report a case presented at our department with complaints of swelling of knee and pain for 1 year. The patient was evaluated and diagnosed with lipoma arborescence and was treated with total synovectomy. There is no recurrence at the end of 2 years of follow-up. In this case report, we describe the case involving the left knee and discuss the clinical presentation, diagnosis, histopathology, and treatment.