Plica syndrome is a disease in which a membrane called Plica that does not create problem normally, create pain in the knee. Plica usually is inside the knee, that is part of the knee that is close to the contra lateral side. Plica normally does not create problems. Sometimes in specific physical activity and constant movement in the knee this membrane is stimulated. To help the diagnosis, the physician may use imaging methods such as X-ray, CT scan, and MRI. Diagnosis is usually made using Arthroscopy by directly observing the knee joint. A 43-year-old housewife who was the resident of Sanandaj had Pain in the knee area and came with a rattletrap knee caused by a sudden blow. She had knee swelling in the upper region. After visiting by orthopedic surgeon and performing a physical examination of the knee, MRI was requested. Following MRI, in addition to joint effusion, Plica syndrome was diagnosed.