Herein we report a case of patellar aneurysmal bone cyst of a 32-year-old female patient who was admitted to our outpatient clinic due to the swelling on her left knee. She was describing no trauma history but increasing pain and that the mass was expanding gradually by the time. Although it occurs rarely in patella, evaluation by radiographic and magnetic resonance images revealed that the mass was due to the patellar aneurysmal bone cyst, which also destructed the surface of the joint. Although there was no impairment in the range of motion of the patient's left knee in the preoperative evaluation, because of the destruction, we performed total patellectomy and extensor mechanism reconstruction by Zaricznyj technique instead of curettage and grafting. The patient was satisfied with the procedure performed after the surgery and there was no complication in the follow-up.