What Is the Iliacus Muscle and Why Is It Causing Tightness in Your Hips?

It’s time to show this crucial muscle some TLC with these exercises.

At some point or another during your running career, you’re likely to experience achy hips. It’s a common complaint of many runners. In fact, one scientific review shows that hip pain is so common among runners that athletes and their coaches and trainers should advocate for practices that continuously minimize risk of hip injuries, and that the best way to do that is to get to the root cause of the issue.

Translation: You don’t have to live with tight hips or hip aches on the run. You just have to figure out what’s causing the issue. And that’s precisely why you want to pay attention to the iliacus, a small hip flexor muscle that can often cause discomfort.

What is the iliacus muscle?

One of the first pieces of advice a runner with hip pain will often hear is, “you need to stretch your hip flexors.” And it is a good recommendation—stretching the hip flexors is something that every runner should do on a regular basis (that means every time you run). But before you effectively address your hip pain, you’ll need a quick anatomy session.

In anatomy lingo, “hip flexors” refer to a group of three muscles located in the front of the hip—the psoas major and psoas minor (the pair is simply referred to together as “the psoas”), as well as the iliacus muscle. Collectively, this muscle trio form what’s known as the iliopsoas, and while there are technically additional muscles that aid in hip flexion, the iliopsoas is our body’s most powerful player in this movement.

Of the group, the psoas is generally the star of the show, getting all the “glory” of being the prime suspect when it comes to hip tightness.

“When people think of hip flexors or hip pain or hip tightness they have a tendency to just think of the psoas,” says Jessica Warneke, P.T., D.P.T., O.C.S., founder of PACE Physical Therapy in Austin, Texas. “But if I’m feeling a nagging pain or a nagging tightness and I’m doing all these hip flexor stretches and it’s not helping, well, I’m missing the root cause of it.”

The root cause may then be the other, often overlooked muscle in the iliopsoas group that isn’t addressed during hip flexor stretches—that is, the iliacus.

“People, even physical therapists, talk about the iliopsoas as though the psoas and the iliacus are the same muscle. But [the iliacus] really is a separate muscle that has a different function. It’s even enervated by different nerves in the body,” explains Christine Koth, M.P.T., a holistic physical therapist and author of Twisted Hip Tight Core: The Key To Unresolved Pain.

“You have to think about the psoas and the iliacus separately—they both are hip flexors but that’s the only thing they really have in common. The psoas is a long muscle that actually crosses three joints,” Koth explains. “It goes from your spine all the way down through your body across the SI joint in the pelvis [that’s the joint that links your pelvis and lower spine] and then goes into the hip. So, it’s responsible for integrating movement and creating stability from the spine through the pelvis and through the hip, and it connects the upper body to the lower body.”

Koth continues: “But the iliacus attaches to the pelvis and then attaches on the femur, and because it’s a short muscle and because it’s so super close to the joint itself it’s not designed to be a mover [like the psoas]… It’s designed to stabilise.”

The stabilising function of the iliacus makes it a crucial muscle for runners to pay attention to because it’s quite literally involved in every single stride. “If you are creating a lot of movement through your body, which runners do—they constantly have to absorb force as their foot hits the ground, one leg is forward and the other leg is back—you have to stabilize your core and your pelvis and the iliacus works really hard in that scenario,” says Koth. (Just think about how much stabilisation you need standing on one leg, let alone when you’re running and adding high-impact to that single-leg stability.)

Another major culprit that contributes to a tight iliacus is something that we all do to excess: sitting, says Warneke.

“If you’re sitting for a long time, that requires a lot of stability, especially if you’re sitting with good posture, because you’re sitting there stabilising yourself. So in that case, the iliacus is active. It’s working,” says Koth. “So runners are kind of the perfect storm for developing a tight iliacus.”

Why is the iliacus muscle so special?

“One thing that’s really important with the iliacus and probably one of the reasons why it’s not talked about much is the fact that it oftentimes doesn’t generate symptoms that show up directly where it’s located,” says Koth. “If you put your finger on that spot [where the iliacus is located] you can potentially feel soreness there but really besides palpating that area, typically people don’t feel that it’s sore right in that spot when they’re running or living their life.”

What you might notice, instead, is your mechanics are off. If our bodily mechanics, such as joint alignment and range of motion are suboptimal, it creates a domino effect of faulty movement patterns. For example, if you’re holding tension in the iliacus, this can lead to pelvis rotation, which might then also lead to irritation of the hip joint itself and also cause knee strain.

Anyone who has SI joint issues, such as pain in the area of the joint or limited hip extension (which occurs when your leg reaches back behind you, like after push-off in the gait cycle) should also be working on their iliacus. “I have never seen anyone with SI joint pain that didn’t have a tight iliacus and that was at the root of the problem,” Koth says.

A tight iliacus can also lead to issues with pelvic floor tightness and pain. “I think that is a very important thing for people to be aware of, especially if they’re runners,” says Warneke.

How can you treat a tight iliacus?

The good news is that the iliacus is easy to find. “If you put your hands on your hips and let your fingertips go toward the front of your pelvis, you’ll find two bones that kind of stick out in the front of your pelvis, those are your ASIS (a.k.a. the anterior superior iliac spine),” explains Koth. “Right inside that bone is a soft spot, and if you kind of curve your hand around the corner of that bone, that’s where the iliacus lives. Because it’s kind of around the corner inside that bone, you need angular pressure to get in there.”

Taking care of the iliacus is a three-step process that involves first releasing the iliacus itself, then releasing the back of the hip, then activating and strengthening the hip flexors and adjacent core and hip stabilizers. While this sounds complicated and time-consuming, it’s not.

Here, the three moves to do. Repeat these every other day until symptoms improve, and then you can maintain by performing them once a week or bi-weekly. (Watch the video above to see these moves in action.)

Step 1: Release the Iliacus

To release the iliacus, we have two options in terms of tools—a 4-inch massage ball or the Hip Hook. To use the ball, first lie on your stomach and place the ball under your pelvis where the iliacus is located. While you lie on top of the ball, use your body weight to apply steady pressure to the area of soreness for about at least 60 seconds while taking deep breaths.

To use the Hip Hook, start by laying on your side. Then, align the tip of the Hip Hook up with your iliacus and roll over onto it until the Hip Hook’s platform is flat on the floor and you’re lying facedown. Make any minor adjustments necessary to line up the tip of the Hip Hook with a tight spot in your iliacus and then relax and settle in, taking deep breaths—this will likely feel intense.

Once you’ve applied pressure for at least 30 seconds, press down on the handle of the Hip Hook to apply angular pressure to really access and release the iliacus. Hold here for about 60 more seconds, or until you feel the muscle release.

“Each time you use these tools it will be slightly different,” says Koth. “There might be a certain angle that feels tight today and that same angel might not feel tight tomorrow. So your first step is to identify which area or which position where the ball or the Hip Hook is placed that feels the most tight, and you can move around a bit to discover that. Once you find it, you want to stay on that spot and hold it. Don’t wiggle around. If you really want to get the most long-term benefit you need to just stay on that spot.”

Step 2: Release the Back of the Hip

To release the back of the hip, lie flat and your back with both knees bent and placed flat on the floor. Then lift your hips slightly and place the ball under the muscle tissue next to the tailbone and lie on the ball. Look for a sore spot—there will likely be more than one! Once you’ve found an area that’s tender, repeat the same method used for the front of the hip: using your body weight, apply prolonged pressure of at least 60 seconds to each sore spot, or until you feel the muscle release and the soreness subsides.

Step 3: Strengthen the Iliacus

Now that you’ve released your iliacus, the next step is to gently strengthen the muscles in the front of the hip. “When we’re having chronically tight muscles, and our iliacus or psoas muscles are tight and we’re not doing anything to properly load them, strengthen, and dynamically train them to work with our core or with our glutes, that is going to keep them in the cycle of them being tight,” says Warneke.

To address strength in the hip flexors, turn to resisted marches: Put a mini band with light to medium resistance around the balls of your feet. Then, stand tall with good posture, feet about hip-width apart. Slowly lift one knee at a time in a marching motion, keeping the foot flexed, the core engaged and the spine and hips neutral. Avoid leaning from side to side as much as possible as you raise the leg. Instead, engage your core and feel your hip musculature stabilising you. Repeat 5 times per side.

“The band provides a good tactile cue, and it’s key to keep your spine straight and in neutral, so you’re not arching your back when you march; then you can lift and flex the hip up. It’s actually deceivingly challenging,” Warneke says. “People think that marching will be easy, but if you’re doing it correctly and stabilising with the right muscles, then you can really feel how it’s working.”

How long does it take to feel results?

Another thing to note when releasing the iliacus is that it takes time. The aches might feel worse when you first apply assisted pressure to release the illiacus, but it should feel better after about 30 seconds. “If it doesn’t start to get better, then you know you’re not on a spot that’s ready,” Koth says.

As with most things, consistency is key in making sure your iliacus stays healthy and happy. “When people first start doing something like this, especially if they’re in a lot of pain, I would recommend giving a day or two break in between each session, and only finding one or two spots each time,” says Koth. Eventually, you’ll lie on the ball or Hip Hook and feel much less soreness or tightness. And that’s when you’re in the maintenance phase.

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