The vastus medialis muscle is very important for the function of the knee joint. We report three cases of a tumor in the muscle accompanied by pain and functional disorders. Two cases had pain on flexion and one case had an obvious limitation of flexion of the knee. The tumor was excised in all three cases. Histological diagnosis of each tumor were lymphangioma, intramuscular ganglion, and intramuscular hemangioma. The pain disappeared in all patients after the excision. However, pain recurred in the patient with lymphangioma and another operation was performed, which helped alleviate the pain again.
