The most important muscle you've never heard of… the iliacus
This is a muscle that you may not even know you have inside your body. Many people don't even know that they exist, let alone what it does to impact your function, impact your ability to stay out of pain, impact your ability to live more and hurt less. You may be wondering what this muscle is, and I'm here to tell you that that muscle's name is the iliacus. You may have heard of the hip flexor; that might have been something that you've come across. A hip flexor is a descriptor of a type of motion. It's a way that the leg moves forward, like a marching motion, and that's called hip flexion. Hip flexors are a group of muscles that are considered responsible for that motion, and one of those muscles is called the iliacus. The iliopsoas is a combination of two muscles: the iliacus and the psoas muscle. When you see these words, it might be hard to pronounce them, so I use the cute image of a “Silly Yak Kiss” to help you remember how to pronounce iliacus, and psoas is pronounced like “So-As.”
Now that you understand how to pronounce these words, you may be wondering what's the deal with these muscles and why the psoas and iliacus are important. The hip flexor is really the iliopsoas, it is made up of two muscles: the iliacus and the psoas. Now in the field of medicine and in health and fitness, the psoas gets a lot of attention. The psoas has become very popular recently. It's very large, and it takes up a lot of space, the job of the psoas is central to keeping the spine connected to the lower body and keeping the function of the core intact. This muscle, the psoas muscle, does get very tight. It can tighten because it's overused, it can get tight from too much sitting, and a lot of the same things affect the iliacus as well.
The iliacus is connected to the psoas
I wrote the book Tight Hip Twisted Core because the iliacus – the twin, the next-door neighbor, the true companion to the psoas – is undertreated and underappreciated. People assume that because they release their psoas, or they're doing hip flexor stretches, they're addressing the iliacus. This is an assumption that is actually false. The iliacus is its own separate muscle. Just because it shares the attachment point of the psoas does mean that it should be grouped with the psoas muscle. In fact, I've seen time and time again people who have worked on addressing their psoas muscle, and have had temporary relief, but once their iliacus was also addressed and released, their relief became more long-standing. The iliacus muscle, I believe, is something that isn't treated, and is overlooked in a lot of treatment protocols and athletic endeavors because it is grouped with the psoas.
The iliacus is located right inside the hip bone, and it's a hard muscle to reach on your own; you have to curl your hand on the inside of your bone. It's awkward, and it's hard to get to, whereas the psoas is more directly into the abdomen, the iliacus is around the corner of the bone.
A tight iliacus affects the whole body
I hope to address these things by teaching you more about how this muscle impacts the body, and how to access the muscle. The function is slightly different from the psoas. It only connects to the inside of the pelvis and attaches to the leg bone. Because of that, it's really commonly involved in pulling the pelvic bone forward, which changes the orientation of where the ball fits into the socket in the hip. That rotation forward also affects where the tailbone and the pelvic bone intersect and can cause lower back pain or issues with the tailbone, or sacroiliac joint. All of these things have this chain effect. It starts with tightness in the iliacus, which persists for years and years, it's pulling on the bone, it's creating a faulty movement pattern in the leg, which then puts a strain on a different part of the body. It could strain the hip, the IT band, the knee, the foot, the toe, the lower back, etc. Eventually, that starts to wear away and then results in the eventual thing we are trying to solve, which is our pain. It's the start of the whole chain of events that leads to us having to do something to get ourselves out of our pain.
I uncover these issues and more in my bestselling book, Tight Hip Twisted Core - The Key to Unresolved Pain!
This is also why I designed The Hip Hook, the world's first tool designed to reach the iliacus through angular pressure, releasing both the psoas and the iliacus muscle.