Physios love an acronym but SIJ is often the most misunderstood and poorly treated area of our anatomy. What is it? The Sacro-Iliac Joints are where you pelvis bones (ilia) join the base of the spine (aka the sacrum). Saying SIJ often gives non-clinical people random knowledge cred down the pub too ‘my SIJ is often out’ .  Impressive.

Yet this is an area even many experienced clinicians fail to treat adequately due to the complex articulations with the back and the pubis, and differing types of symptoms associated.

Despite being in a world that strives for equality, the male pelvis is smaller and narrower while a female pelvis is wider and roomier. So what do these differences mean?

Well essentially these joints lock into a stable (close-packed) position in weight bearing so forces can be distributed up through the spine in both men and women. So if one isn’t stable then people can get pain with walking, landing on a foot or even when lifting a leg when lying down.

However we more often identify issues with women during or following pregnancy as the hormone relaxin is released and causes loosening of the ligaments of the joint so it can widen for birth. Having too much or too little motion at the SIJs can cause inflammation of the joints.

That said, hypermobile joints are common in both men and women and we can sometimes see pain associated with an unstable SIJ. This unfortunately is not likely to resolve itself as it can slip up or down and may need manual correction by a therapist. Furthermore it will probably need some retraining of the surrounding deep muscles that keep things stable.

So if you or know someone who complains of pain in the pelvis/back/groin typically with putting weight through one leg, lying on one side or lifting one leg off the floor, it’s probably time to get those SIJs looked at.