The Sacroiliac joints are located at the very bottom of the back. You have one either side of the spine. The Sacroiliac joints help make up the rear part of the pelvic girdle and sit between the sacrum (vertebrae S1-S5) and the Ilia (hip bones).

The function of the SI joints is to allow torsional or twisting movements when we move our legs. The legs act like long levers and without the sacroiliac joints and the pubic symphesis (at the front of the pelvis) which allow these small movements, the pelvis would be at higher risk of a fracture.

The concept of the SIJ causing lower back pain is now pretty well understood. However, due to the complex anatomy and movement patterns at the joints and area in general, evaluation and treatment of sacroiliac dysfunctions is still controversial.

SIJ dysfunction is a term which is commonly used when talking about sacroiliac injuries. This dysfunction refers to either hypo or hyper mobility (low or high respectively). Or in other words, the join can become 'locked' or be too mobile. This can then lead to problems with surrounding structures such as ligaments (e.g. Iliolumbar ligament) and muscles, which means SIJ problems can cause a wide range of symptoms throughout the lower back and buttocks, or even the thigh or groin.