Sacroiliac joints are paired C-shaped or L-shaped joints capable of a small amount of movement[2] (2–18 degrees, which is debatable at this time) that are formed between the articular surfaces of the sacrum and the ilium bones. The joints are covered by two different kinds of cartilage; the sacral surface has hyaline cartilage and the ilial surface has fibrocartilage.[2] The SIJ's stability is maintained mainly through a combination of only some bony structure and very strong intrinsic and extrinsic ligaments.[3]