5 Things We Didn't Learn About the SI Joint in Yoga Teacher Training

Today I'd like to offer 5 insights about the SI joint (or sacroiliac joint) that we don't tend to learn about in yoga teacher training, but which definitely have implications for how we teach and practice yoga. Also included are multiple scientific references for each point. I invite you to read these points with an open mind and a willingness to possibly question your own biases (because I know I have had to question my own many times as I continue to study and learn about the body!)



Insight #1: The SI joint is a strong, resilient structure that is supported by thick layers of some of the strongest ligaments and muscles in the body. [Ref, Ref, Ref]

Although the SI joints are some of the strongest joints in the body, we often receive the impression from our yoga teacher trainings that they are actually quite fragile structures that are vulnerable to injury and instability from the slightest misalignments in yoga. For example, we are sometimes taught that if we hold our pelvis "square" when we twist in poses like twisting triangle (parivrtta trikonasana), we can "tweak" our SI joints by pulling them out of alignment, and we should therefore instead always be mindful to let our pelvis turn slightly in the direction we are twisting in these poses. Another example is that we are often instructed in backbends like bridge pose (setu bandha sarvangasana) and locust pose (shalabhasana) to relax our glutes (or to at least soften them somewhat) because if we contract them too hard, this could injure our SI joints.

One reason we tend to believe that our SI joints are vulnerable to damage in yoga is that we generally learn about SI joint anatomy by looking at a skeleton model or a drawing like this one here:


When we see the bones by themselves like this, we can certainly get the impression that the sacrum can "slide around" relative to the pelvis easily, resulting in an SI joint that can be pulled "out of place" or "strained" due to small misalignments in yoga poses.

However, what we rarely see after learning about the bony anatomy of the SI joint's structure is an image like this, which depicts all of the extremely resilient, tough ligaments that surround and support the SI joints from all sides, holding them firmly in place:

The ligaments that support the SI joint include the anterior sacroiliac ligament, interosseus sacroiliac ligament, sacrotuberous ligament, posterior sacroiliac ligament, and sacrospinous ligament.

The ligaments that support the SI joint include the anterior sacroiliac ligament, interosseus sacroiliac ligament, sacrotuberous ligament, posterior sacroiliac ligament, and sacrospinous ligament.


A rarely-cited fact is that the ligaments of the SI joint include some of the strongest ligaments in the human body! [Ref]

If after seeing an image of the SI joint's ligamentous support, we were then shown an image like this one below, which depicts all of the thick musculature and fascia on top of all of those ligaments on top of the SI joints (including the powerful gluteus maximus, the largest muscle in the human body), we might have reason to be more confident and less fearful about this naturally strong, sturdy area of our body:



While our SI joint can certainly be injured and we can absolutely experience pain there (more on this in #4), it would take much more force to injure a healthy SI joint than the relatively low loads involved in a yoga practice.


Insight # 2: The SI joints are inherently stable by design, not inherently vulnerable. [RefRef, Ref]

The SI joints serve to transfer the load of the upper body to the lower body, as well as to distribute forces moving up the body from below. Therefore, stability is built into their very design so that these forces can be transferred efficiently through the pelvis.

In fact, the SI joints are so inherently stable that there is only the tiniest amount of movement available at these joints. While some sources state that the amount of motion available at the SI joint is a barely-perceptible 2-4 millimeters, other sources actually state that there is in fact no movement available at these joints at all.


Insight #3: Even if the SI joints could "slip out of place" easily, we don't have a reliable way to assess this in someone's body. [Ref, RefRef, Ref, Ref]

SI joint movement is so minute and difficult to identify with either manual palpation or radiographic imaging that none of the tests traditionally done to assess the SI joint have been shown to be reliable. Without an accurate method for testing the position and movement of an SI joint, how can we definitively know that someone's SI joint is "out of place", "misaligned", or "unstable" in the first place?


Insight #4: SI joint pain is certainly a common experience among yogis and non-yogis alike, but SI joint pain does not necessarily mean that there is an SI joint injury. [Ref]

His left hand would actually be a bit lower if this were truly SI joint pain. (I couldn't find a photo that showed the right spot - they all seem to feature general low back pain instead!)

His left hand would actually be a bit lower if this were truly SI joint pain. (I couldn't find a photo that showed the right spot - they all seem to feature general low back pain instead!)

Thankfully, insights from modern pain science are beginning to become more widely known in the yoga world, but if this topic is new to you, consider taking a look at the introduction to pain science article that I wrote for Yoga International a couple of years ago. It turns out that despite what we have traditionally been taught, pain and tissue damage often do not correlate on a 1:1 basis - especially when pain is experienced in a more persistent or chronic way. Pain is actually a much more complex, multi-factorial phenomenon than simply "I have tissue damage and therefore that is what is creating my pain."

As an example, if someone has SI joint pain and they have experienced a recent blunt force trauma to their pelvis region (think from a car accident or a major fall of some sort), then their pain is very likely due to an actual SI joint injury. Once this injury has healed, this pain should subside. In fact, my husband and I suspect that his SI joint may have been injured many years ago in yoga by a strong adjustment he received. His yoga teacher forcefully pulled both of his legs behind his head in a pose called dwipada sirsasana and he felt a searing pain at his left SI joint in that moment. Thankfully the injury healed, but this type of forceful, deep adjustment seems like it was enough to cause injury to his SI joint (or at least a strong protective output of pain in the area).

But in contrast to those examples of short-term pain associated with acute injury, when someone's SI joint pain is more long-term or chronic in nature (chronic pain is sometimes defined as pain lasting longer than 3 months), it's less likely that this pain is connected to a specific injury or damage to the area, and more likely that the person's nervous system is instead sensitive around that spot. Nervous system sensitivity and an output of pain can be the result of many different factors aside from actual tissue damage. Other influences include emotions, past experiences, stress levels, beliefs - and particularly beliefs about one's body. In fact, the more that someone believes that their SI joints are fragile and vulnerable, the more likely their nervous system is to perceive threat in that area and to output pain there. And conversely, the more someone learns that their SI joints are strong, inherently stable structures well-supported by some of the most durable ligaments and muscles of the body, the less likely their nervous system will be to perceive threat and output pain in this area. [Ref, Ref]


Insight #5: Warnings about protecting the SI joint in yoga are often unnecessary.

As we have seen, the SI joints are held stable by a ligamentous and musculature support structure that is strong and resilient - and the joints themselves have only a tiny amount of movement available (if any) in the first place. With this in mind, whether or not we hold our pelvis square when we twist in yoga is probably not a likely mechanism for SI joint injury either way, given the relatively low loads involved in the pose. And whether or not we squeeze our glutes in backbends in yoga is also unlikely to be a mechanism for SI joint injury; in fact, contrary to the common cautions in yoga, contracting our glutes in backbends has actually been shown to have a positive stabilizing effect on the SI joints. [Ref, Ref]

Additionally, it's common these days to hear warnings about "overstretching" the ligaments of the SI joints in yoga poses, leading to SI joint instability and pain. (I myself used to offer such cautions too - the idea just seems to make sense!) We are learning, however, that this is not actually how ligaments respond to stretching. During a stretch, a ligament lengthens temporarily, but then it returns to its resting length afterward (sometimes after a short recovery period.) Despite popular warnings, passive stretching has not been shown to lengthen and destabilize ligaments and joints. I have personally changed my perspective on this issue due to insights from newer research and teachings from my yoga biomechanics mentor Jules Mitchell.

(For more reading on the fascinating topic of stretching, ligaments, and joint instability with lots of research references cited, I encourage you to read this recent blog post by Greg Lehman, a researcher and clinician whose work I have followed and admired for quite some time now. But fair warning: this post is long and is really territory for the more serious body geeks among us. You can always jump right to "Questionable Assertion #3", which specifically addresses these topics and might offer some new, interesting information for you to ponder.)



In summary, SI joint pain is common among yogis and non-yogis alike and there are many factors that can contribute to it, including physical, psychological, and social ones. How we align our body in yoga is probably not a mechanism for SI joint injury, though (strong, forceful adjustments by yoga teachers excepted!) Rather than worrying too much about alignment for SI joint protection, a more effective means to injury-prevention is to simply strengthen and condition the muscles and connective tissue that support the SI joint, so that their capacity to handle load increases.

Thank you for reading these 5 points with an open mind, and I hope to see you on the mat virtually or in person in the near future!

What Does Your Twist Tell You About The Strength Of Your Core?

We know it’s important to have a strong, functioning core. But did you know that working our core muscles is only one half of the core strength equation? In order for our core to be truly strong, it must also be flexible and supple. As counterintuitive as it may seem, mobilizing our waist area with poses like twists has just as much to do with core strength as “core work” does. However, the traditional alignment we use for our twists in yoga often misses this important core strengthening benefit. In this article, we’ll use biomechanics to uncover some common twisting “cheats” so we can turn our twists into the awesome core-focused poses they should be!


(Update, February 2016: I really appreciate the sentiment of this section of this post, but since the time that I wrote it I have learned more and shifted my perspective. The term "tight" does not have an objective, scientific meaning, and there is also currently no evidence that I know of that suggests that strengthening a muscle will cause it to become 'short and tight', even though this a very commonly-held belief. I still love this blog post in general (especially the great photos of twisting alignment below), but this specific section right here is a tad outdated now.)

The first time I heard the statement that tight muscles are weak muscles, I was certainly dubious. Everyone knows that short, tight muscles are strong while long, loose muscles are weak, right? Isn’t that the way the body works? But it turns out that this common belief is actually an anatomy myth that doesn’t hold true once we examine the science of musculoskeletal function. It is correct that in order to be strong, a muscle must be able to contract - but this is only half of the movement equation. For true functional strength a muscle must have the ability to both contract and release.

When we talk about whether a muscle is strong, we’re really referring to how well it can “generate force”. This takes place at the level of the sarcomere, the basic contractile unit of a muscle. When a healthy muscle contracts, its sarcomeres generate force by shortening, and afterward they release and lengthen again so that they’re ready to shorten the next time the muscle is asked to contract. But if we work our muscles so much that they become short and tight, their sarcomeres are now in an overlapped, “locked short” position and can no longer release back to the place where they can contract again. Muscles like these are not functionally strong because they have a very limited ability to generate force.

So what happens to the muscles of our core if we “strengthen” them with a bunch of core work until they become short and tight? We might end up with defined abdominal muscles like your stereotypical six-pack abs, but if at the micro level, our sarcomeres are overlapped and can’t release back to their optimal force-generating position, our core is not physiologically strong.



For today’s purposes, let’s define the “core” as the area between the rib cage and the pelvis. We now understand that in order for this area to be strong, the muscles and fascia that live there must also be supple. One of the best ways to mobilize these tissues is through twisting. A twist takes place when we rotate our rib cage relative to our pelvis, our pelvis relative to our rib cage, or both at the same time.

Here’s a great visual that demonstrates this movement. My top hand represents a rib cage, my bottom hand is the pelvis, and the blue fabric in between is the muscles and fascia of the core:

No twist has taken place here because the rib cage and pelvis are facing the same direction.

No twist has taken place here because the rib cage and pelvis are facing the same direction.

Successful twist! The rib cage and pelvis have rotated relative to each other (see how the hands have turned?) and there's clearly a twist in the blue fabric.

Successful twist! The rib cage and pelvis have rotated relative to each other (see how the hands have turned?) and there's clearly a twist in the blue fabric.

Ideally a twist in our body would mobilize the muscles of our waist in the same way that these hands mobilized the blue fabric. Most of us are actually much stiffer through the waist than we realize, though, meaning that our true twisting range of motion is relatively small. But because of a prevailing idea in yoga that going "deeper" in a pose is better, we tend to bypass placing a load on the tight tissues of our waist in favor of moving where it's already easy for us to move, ending up in a shape that creates the illusion of a twist without mobilizing our core muscles much at all. Let me show you what I mean.

Here’s a wonderful yoga student named Craig (who also just happens to be my husband!)

Here are a few places where Craig can move really well in his body:

He can move nicely at his neck - see how he can turn his head all the way to the side?

He can move nicely at his neck - see how he can turn his head all the way to the side?

He can also move his arms relative to his torso with ease.

He can also move his arms relative to his torso with ease.

In fact, Craig can combine these two movements to create a quite aesthetically-pleasing twist, wouldn’t you say?

But wait... is this a twist? Or does it just appear on the surface to be a twist? Well, if you use your anatomically-informed eyes to look at the Ganesha print on the front of Craig’s shirt, you’ll see that Ganesha is facing straight forward - he didn’t move through space at all. If Ganesha didn’t move, then Craig’s rib cage didn’t move, which means that his core didn’t receive a stretch at all, and this shape was, in fact, a twist “illusion”.

Another easy way to miss your best twist is to lift your chest instead. If we arch our spine when we twist, we’ll feel like we’re deeper in our twist because we moved more, but we’re simply mobilizing a place that wasn’t the target area of our pose - with the added drawback of creating compression in our lumbar spine. This kind of twist looks something like this:

Do you see how Craig has lifted his chest and tilted his rib cage backward in this example? He has also let his head rotate much further around than his rib cage, and if you look closely, you’ll see that his eyes have moved even further around than his head (!), all of which makes Craig feel like he moved deeper into his twist, when in reality his core didn’t rotate much at all.

In this final example, Craig is demonstrating a true core-mobilizing (and therefore core-strengthening!) twist:

He hasn’t arched his spine to create excessive movement in non-optimal places, and the change in angle of Ganesha shows us that he successfully turned his rib cage relative to his pelvis. An aligned twist like this is the essential ingredient to core strength that many of us have been missing. Your body will love it when you find it!



In our continuing pursuit of an updated yoga practice that’s informed by biomechanics and anatomy, it’s helpful for us to look beyond the oversimplified categories we’ve been taught for our poses. “Spinal twists” and “core work” are actually intimately connected when it comes to core function. And as has become a central theme of my blog posts, in order for our twists to have a beneficial impact on our core, we need to let go of the idea that “deeper is better” and learn to work within our body’s true limits. The path of seeing ourselves accurately and clearly is an essential key to the transformative effects that yoga has to offer!


Related Online Class: Twisting-Focused Flow

Related Online Workshop: Anatomy of the Spine for Increased Core Connection