Understanding the Sacroiliac Joint
Asana Anatomy-Understanding the Sacroiliac Joint
Controversy does not often strike the yoga community. Non-harming, truthfulness, and loving kindness are not very controversial concepts. Yet the poor, barely mobile, sacroiliac joint has become the center of a yoga debate – to square or not to square the hips. Ok, so it is not as racy as a celebrity feud, but it may affect your personal yoga practice.
Let’s dissect this joint.
The two sacroiliac joints (SI joint) are formed by three bones: the triangular sacrum bone, and the two wing like bones of the pelvis known as the ilium. Each iliac bone (one half of the ilium) comes in contact with one side of the sacrum, forming two SI joints. This connection is like three puzzle pieces fitting together known as form closure. Form closure creates stability, keeping the pelvis together in one unit. The SI joint itself is shaped like a boomerang with two arms at 90 degrees to each other. The upper portion lies in an up-and-down orientation and the lower portion lies in a front-to-back orientation. The surface of the joint is covered in coarse cartilage, adding friction and contributing to the force closure.
The sacrum moves in nutation (forward) and counter nutation (backward) in relation to the ilium. The sacrum can move only on one side, like in lifting one leg, or both sides, like when we move from lying to standing. This movement is very small, amounting to 1 or 2 mm of motion in either direction. As we age, the sacrum becomes wedged increasingly forward, but this doesn’t fully happen until we reach our 30’s. This wedging increases the resistance to shearing (twisting) forces across the sacroiliac joint. Herein lies the problem. The SI joint is a joint that is intended to provide stability for the pelvis, and is not built to move.
The SI joint has another mechanism of stability – force closure. This is the stability created by the action of the core musculature that has attachments into the SI joint – namely, the muscles of the pelvic floor, and the transverse abdominis. Conveniently, we can access these muscles through the activation of the bandhas or energy locks in yoga. In mula bandha we imagine a subtle lifting up of the muscles we use to control the flow of urine. In women, activation of this musculature has been shown to provide force closure for the SI joint. In uddiyana bandha, we draw the lower belly in and up, activating the transverse abdominis muscle. For this version, the scooping of the lower belly needs only to be subtle, and slightly flattens out the lower abdomen.
Hip Opening or Sacroiliac Opening?
Many of us identify ourselves as having “tight hips”. For many, this means a lack of external (outward) rotation at the hip joint. Using the example of Virabhadrasana I or Warrior I pose, our front hip is in a flexed position with toes pointing straight ahead. Our back foot is on the floor at a 45 degree angle, and in order for the points of our hips (our iliac crests) to face toward the front of the mat, our back hip needs to extend, and externally rotate. If we look deep inside we see that these actions require our sacrum to nutate forward on the side of the lead leg, and counter nutate backward on the side of the rear leg. If the rear hip resists external rotation in order to square the hip points forward a twisting or shearing force is introduced across the SI joint. Over time this can lead to irritation, hypermobility, and dysfunctional firing patterns of our pelvic musculature.
Happy Sacrum
This situation is an opportunity to practice ahimsa or non-violence towards our SI joints. There are a few ways you can diminish the shearing force across the SI in standing poses. The first is to take a slightly wider stance, opening your feet to hip width (rather than heel to arch or heel to heel). This enables your pelvis to comfortably square forward. Another option is to keep the feet as they are and simply allow your pelvis to be slightly open to the side of your mat. That’s right, let go of the desire to perfectly square your pelvis forward. Instead, imagine the hip bone in its socket, outwardly rotating. Keeping that rotation, tuck the tailbone under slightly, creating room in the front of the hip. You may find that this provides more freedom of movement and may naturally square your hips further. In standing and seated twists, be sure to engage the muscles of the pelvic floor (mula bandha) to support the SI joint before twisting.
When we step back for a moment and acknowledge the true purpose of our yoga practice, suddenly trying to make our bodies fit a mold doesn’t make much sense. Being more forgiving and accepting of our bodies limitations enables us to go much deeper into our yoga practice and experience the joy of yoga safely. Now that doesn’t sound controversial at all.
About the Author
What Really Happens in Hip Openers
One of the most common requests heard in a yoga class is hip openers today please. This request is usually followed by the other half of the class groaning. We love to hate hip openers yet our bodies crave them and often feel lighter and more open after — for good reason. The majority of us sit for most of our days, shortening the hip flexors at the front of the hip (psoas, rectus femoris, sartorius) and tightening the hip rotators (piriformis, obturator internus, gamellus, to name a few).
A Look Inside the Hip
The hip joint itself is a ball and socket type joint with the head of the femur (thigh bone) sitting in the acetabulum or socket of the pelvis. A variety of muscles attach into the femur starting from the pelvis itself, the lumbar spine, the sacrum, or other parts of the femur. Hip openers could affect any of the muscles surrounding the hip depending on the position of the joint at the time of the pose.
In general when we stretch or open a muscle we are lengthening its position, moving the two attachment points away from each other. This is easy to assess with linear muscles like the psoas which attaches from the front of the lumbar spine, crosses through the pelvis and attaches to the head of the femur. If we flex the hip forward we are shortening the psoas, bringing the two attachments of the muscle closer together. If we extend the hip backwards (such as in the back leg of Pigeon pose we are opening and lengthening the psoas. The effect becomes greater in King Pigeon pose if we assume an upright posture with our spine so that we lengthen the upper attachment more. In this example we can also rethink our definition of hip openers. Suddenly, poses with a bent knee where we rotate the hip are not the only way to open our hips. If the psoas attaches into the femur, and a shortened psoas tightens our hip (not to mention the affect it has on our low back) then poses like Warrior / Virabhadrasana or Half Moon / Ardha Chandrasana become hip openers too.
Rotate to Open a Rotator
The rule of how to open a muscle becomes less clear with the hip rotators where the angle of the joint actually affects the action of the muscle. For example, the piriformis muscle attaches from the front of the sacrum to the back of the femur. It acts as an external or outward rotator of the hip. Except if the hip is flexed, then it assists in abduction or sideways movement of the hip. So to follow the rule of opening we would want to internally rotate the femur, flex the hip and adduct or bring the femur towards midline. This can be achieved with the top leg in Marichyasana (sit with your left leg extended, bend your right knee and step the foot across your left thigh so that the femur is flexed, adducted toward midline, and gently internally rotated.) Other hip openers don’t seem to follow the rule of opening. We often externally rotate the hip to stretch the external rotators of the hip. Huh? The reason this works is because we typically flex the hip at the same time.
Use Your X-Ray Vision
To understand how hip openers work we have to picture the position of the muscle. Let’s picture the obturator internus muscle, a close friend of piriformis. It attaches from our sitting bone or ischial tuberosity to the greater trochanter of the femur, a bony outcropping on the side of the hip. We can feel both of these pieces of bony anatomy. Our ischial tuberosities can be felt when sitting, they are the bony bits under the flesh of our buttocks. Our greater trochanter can be felt by first finding the top of our pelvis by by placing our hands at our waist, firmly pressing in and down until we feel a ledge. This is our iliac crest. Slide your hands down and with your thumb you will feel a bony prominence that is the femur. You can feel it move by slowing rotating the hip in and out. So now we can feel the attachment points for the obturator internus, between the ischial tuberosity or sitting bone, and our femur. From this observation we can see that in a neutral position the muscle wraps around the hip. So if were to flex the hip, the ischial tuberosity scoops under thus increasing the space between the two attachment points and increasing the wrapping distance of the muscle – hence lengthening the muscle. This is why a simple squat (using the term simple lightly) can stretch our hip rotators and can be one of the reasons Westerners find it so challenging to achieve.
Opening Our Hips to Open to Possibility
Since there are many muscles in the hip with many functions depending on the demands we place on our body, keeping these muscles supple can help us in ways that may not seem obvious at first. Hip openers may help us attain a standing pose we’ve been struggling with, or they may help us get down on the ground easily to play with our kids or our kitten. Traditional yogic thought attributes many healing properties to hip openers from organ issues to sexual dysfunction. So if you are one of the groaners when hip openers are suggested, perhaps pause to wonder if they could be helping you in ways you weren’t even aware.
