Hands on your hips ... that's it

A pelvis in the wild.

Three or four years ago, in setting out to contribute to the body of knowledge of your body, I always planned to unfold the mysteries and nuances of the Sacro Iliac Joint. I see it fairly frequently, but I thought it might not seem as exciting as writing about Rocky Mountain Spotted Fever, or Arnold-Chiarelli Syndrome, but if it were a movie, it would be a gripping yarn, minus the explosions and the headline A list actors. Judge for yourself, and you will probably agree, you would wear the "I Love my SIJs" T-shirt by the end of this article.
The Sacro Iliac joint is a little like your Jaw - two joints from one bone articulating with a larger structure. In this case it's the sacrum which forms the back part of your pelvis.
The best description of this area comes from our friends at Fountain Lakes, where Kath calls her daughter Kim's furry tailbone her welcome mat. The sacrum fits snugly between the rigid embrace of the two Ilia, the round and wide parts of the pelvis. The pelvis has successfully masqueraded as another body part: hands on hips!
If you have heeded the call to place your hands, I will wager you have your hands on your Ilia.
If you authentically place "hands on hips" you will in fact have mastered the low hand greater trochanter model pose that looks neither sexy or practical.
A nuance of this structure is that the sacroiliac joint has a dual nature. It is two types of joint in one. On the one hand it has the characteristics of a regular synovial joint that encapsulates a nourishing lubricating fluid, and on the other hand, it is a syndesmosis, which being completely Greek to me, means "with a band".
Not so much an adoring groupie following a rock band around the world, but instead the rearward part of the joint has a fibrous band that unites the adjoining bones.
Accordingly, this adds to the joints ability to absorb shock, and deliver reciprocal motion of the pelvis during walking.
The build of the Sacroiliac joint is brilliant in that it combines structural stability from the bony wedge sitting V shaped in the pelvic embrace, with the functional stability from the multi directionally acting muscles. One hypothesis in SIJ dysfunction is a failure in the muscular supports.
If we assume we have four Clydesdales pulling equally on a cart in the four directions of the compass, you would expect the cart to be going nowhere, but the tension applied means it isn't going to be shifted from that nowhere easily either. This might suffice as a crude analogy of how the sacroiliac is stabilised by muscles and fascia. Now lets say south horse gets unwell and suffers a reduction in horsepower.
The system is dramatically altered. The cart is no longer stable in place. The onus is then on the therapist to understand these vectors, or directed forces, and figure out how to bring back the balance.
Nuance two: the hamstring muscle (biceps femoris) attaches to one of the SI ligaments, so tight hamstrings, or an injured hamstring may be one of the opposing horses.
McGill, a prominent biomechanist puts forward the argument that SIJ trouble is not always SIJ but instead dysfunction presents as pain in the region mediated by a myriad of tissue possibilities.
Of particular interest to me is the grey area of the muscular and connective tissue architecture.
Some of the largest muscles in the body terminate at the relatively small surface area of the SIJ.
The huge force generation of the latissimus dorsi are a major contributor in tandem with the opposite buttock to the external muscular bracing I mentioned above.
In measuring peak forces during maximal lifting drills, they found that the total force transmitted to the SIJs would exceed 5600 Newtons of force.
Force is of course mass times acceleration, so it is 560kg equivalent of load, which is easier for the layman to comprehend. Imagine doing that lift several hundred times a day!
So do you have a sacroiliac disorder?
How would you know?
Firstly, your low back pain is usually off centre and around or below the lowest lumbar vertebra. It is mostly one sided but can be off centre on both sides occasionally. Classic signs are difficulty going up stairs and rolling in bed.
Unlike sciatica which is a referred pain down the back of the thigh and into the calf and foot, SI joint pain rarely ventures below the thigh.
For men, an unwelcome pain referral is into the delicate bi-ovoid carrying purse known as the "cod", which is not even helped by the wearing of a cod piece.
Perhaps this garment was more about advertising virility and drawing attention to the region than a therapeutic bracing stratagem. Buttock and groin are also referred pain locales.
An examination might reveal some muscular imbalance in the supporting structures.
This brings in consideration of core structures, the large supportive fascia of the back (thoraco-lumbar fascia), postural alignment, leg length and as mentioned, hamstring length.
The nuances abound when you consider the movement of the sacrum on the pelvis, as five movements are described for a joint that doesn't appear to have much movement.
Treatment is aimed at symptomatic relief initially, and then a move into the wider issues of balance and imbalance, strength of core muscles and stretching tight muscles.
Manipulation, mobilisation, massage are all of value, but are not on their own the solution, as this rehabilitation is the sum of all remedies.
Once more as you look closely at the form and structure, you cannot help but marvel at the craftsmanship and purposeful architecture.
If our pelvis happened to be a solid ring of bone instead, the core features of being able to walk, jump, bend and lift would be unpleasant and unnatural.
Instead the arrangement of several bones making up several joints allows for shock absorption, nimble movement, and the celebrated Cuban Motion as seen in Salsa, Rumba and perhaps regrettably, Simon Barnett more recently.
If you have off centre low back pain, there's a good chance its in your pelvis, which makes for a more colourful diagnosis to share with friends than an obliterated or dessicated disc.
Get it seen to by a physiotherapist with biomechanical expertise.