Diarthrodial joints are freely moveable joints held together by a joint capsule, such as the TMJ, knee and shoulder, as opposed to slightly moveable (amphiarthrodial) or immoveable (synarthrodial) joints, such as the spinal and sutural joints, respectively. [1] They are the type of joint most commonly involved in rheumatological disease. [1] The sacroiliac (SI) joints in the pelvic region are an example of a diarthrodial joint [2]