Baker’s cyst is outpouching of the synovial lining of the knee joint. Occasionally when the patient has fluid in the knee, the fluid may track outside into this outpouching causing it to collect the fluid and swell up that can be felt as a soft swelling of the back of the knee. It is usually treated by the management of the pathology that causes the formation of the fluid as well as aspiration of the fluid from the knee joint. Rarely the Baker’s cyst just needs a surgery to remove it.