Hip-opening classes never go out of style. I get it. When something feels bound up I want to stretch it, and extended periods of sitting can leave the front of my hips feeling stiff.
When I attended my first yoga teacher training over 15 years ago, I learned that the psoas is the primary hip flexor—which is to say that it is responsible for pulling the two halves of our front body, torso and thighs, closer together. This is also how the function of the psoas is defined in most anatomy books.
In the rehab setting where I work as a massage therapist, clients also routinely point to the front of their pelvis and tell me they have a tight psoas. Over the years I’ve become very curious about whether or not the psoas really is the culprit for all the perceived tightness people experience in their anterior hips.
I’m going to share some ways I have learned to assess psoas flexibility, along with some strategies I have found for addressing whatever appears to be restricted.
Most anatomy books claim that the psoas flexes and externally rotates the hip. What they don’t tell you is that its exact function is a matter of debate among researchers.
There are a few reasons for this. At the top, the psoas has broad spinal attachments and it curves and twists before attaching to the thigh bone at the bottom. This unique structure sets it apart from other muscles such as the biceps, which have a more linear structure (and thus a more easily understood function). Additionally, the psoas lives deep in the body, which makes it challenging to test with EMG needles (electromyography measures the activity in a muscle).
One of the more widely known findings about psoas function points to its spine stiffening or stabilizing effect during hip flexion. Echoing this finding are other studies that measured psoas activity during a supine straight-leg raise test, but they also show that it is most active on the fixed (non-moving) hip.
That said, the psoas is more than a hip flexor. While it can flex the hip under certain conditions, other muscles—including the rectus femoris, tensor fasciae latae, and sartorius—are more mechanically advantaged to act as hip flexors because they have a more efficient line of pull. In my experience as a massage therapist, most people with a restriction in their anterior hips improve their hip extension by stretching these more superficial muscles or manually working their soft tissue.
The following self-assessment can provide valuable insight when it comes to determining which areas are limiting hip extension.
Assessment #1: The Modified Thomas Test
Sit at the very edge of a massage table or high bench and hug one knee tightly to your chest. Recline fully and allow the opposite leg to relax and dangle toward the floor. Make sure you don’t arch your low back. If this is hard to maintain, slide a pillow under your buttocks (not your lower back) to place your pelvis into a posterior tilt that helps to round your low back.
(Ask someone to take your photo from the side or set up your camera on a timer.)
If your bottom knee is higher than its corresponding hip, you may have a restricted psoas. Make sure you are fully relaxed and not unconsciously tensing (and thus holding up your bottom thigh).
If your bottom knee is at the same height or lower than your hip and your knee is flexed to about 90 degrees, your psoas length is probably normal.
If your thigh is the same height or lower than your hip but your knee is more extended (not pictured), your rectus femoris (the only quadriceps muscle that crosses the hip and knee) may be restricted.
Now take a photo from the front.
If your top thigh is level with the corresponding hip and the knee appears drawn to the outside of your torso (as in the photo above), your tensor fasciae latae (TFL) may be restricted.
If your knee appears drawn to your midline, it could be due to a restriction of the adductor group.
Compare the two sides.
Note: There are other things you can discern from this assessment that are outside the scope of this article. You can find a more in-depth video on my website.
Assessment #2: Prone Straight-Leg Raise
Lie down in a prone position, and lift one leg as high as possible without extending your low back or bending your knee. (Imagine doing ardha salabhasana with your head and shoulders on the floor.) Ask someone to take your photo and use the ruler feature under your phone’s photo edit and mark up options to measure the degree of hip extension.
If you can achieve 20 degrees of hip extension or more in this position you probably don’t have a psoas length issue. Personally, I like this assessment because it does not require a massage table. However, the Thomas test has the advantage of gravity, which pulls the top leg down. This prone test necessitates having enough strength in your glutes and hamstrings to overcome gravity and the weight of your leg. I suggest trying both assessments and comparing results.
Let’s Say One Psoas Appears Restricted Compared to the Other
I’d like to present some different strategies, any of which can be effective depending on the individual. Some people respond well to stretching restricted muscles while others do not. In my experience, increases in range of motion from targeted stretches alone are temporary. (In a subsequent article I will explore the question of why muscles get tight and what tight means.)
I like to ask questions and then indulge my inner scientist. Here are some of the things I ponder:
The law of reciprocal inhibition suggests that continuously engaging one muscle group forces relaxation on the opposite side of the joint. In theory, continuous contraction of the gluteus maximus should relax the psoas because they are antagonists (and also work synergistically to control the hip joint).
To test this, lie on your side about shin’s distance away from a wall with your back facing it. Place both feet on the wall with your knees bent to 90 degrees, and the rest of your body (from knees to head) in one line parallel to the wall. To avoid extending your lower back, tuck your tail and gently contract your abdominals. (If this position cannot be maintained in your low back, move closer to the wall to slightly flex your hips. Play with your positioning until you can keep your low back from extending.)
Then push your top foot firmly and steadily into the wall. You can do this on both sides or just on the side on which your psoas tested shorter than the other. Hold the isometric glute contraction for 10 to 15 breaths or longer and then reassess your psoas. If your hip extension improves, you have an effective course of action that combines a stretch for the front of the hip with an isometric contraction at the back of the hip.
As mentioned earlier, the psoas has been found to fire most during a straight-leg raise test, but on the side of the fixed hip. The following exercise leans into this finding.
Lie on your back—like tadasana but with more of a posteriorly tilted pelvis. Press your feet into the wall either slightly turned out or parallel. Tuck your chin slightly and flatten your mid spine into the floor. The goal is to maintain this alignment in your entire spine during the exercise. Press into the floor the side that tested shorter, and lift the opposite leg as high as you can while keeping the same alignment in the rest of your body.
If this is not possible, try placing a pillow under your buttocks to help maintain a less extended mid and low back or try keeping your top knee bent (as pictured below) during the leg raises.
You can also try this with the bottom knee and hip slightly flexed by positioning your feet higher on the wall.
Find the method that makes you feel most stable and the least likely to move in your spine. In theory, this will “ask” the psoas on the non-moving side to engage isometrically to stabilize the hip joint and low back. It will not change in length and will thus prevent motion on that side while the other one controls the flex-and-extend motion of the hip.
One option is a high lunge variation. With your right foot in front, turn your back foot in so that your left toes face slightly to the right. Stay tall, gently round your lower back, and side bend your torso to the right. Lastly, mirror a cobra pose in your spine by lifting to any degree your chest toward the ceiling.
For a stretch to be effective, most people need to hold it for at least two minutes, so if this position is too challenging, choose an equivalent position that you can comfortably maintain. After the passive stretch, gradually pull the back leg energetically forward to isometrically engage the hip flexors. Increase the intensity of that contraction until you are working at 100 percent effort but without pain. A cue I use here is, “Picture your back foot glued to the floor and try to pull it forward as hard as possible.” Then, gradually and isometrically engage the muscles at the back of the hip by squeezing the hamstrings and buttocks to fatigue. A cue I then use is, “Now pretend the back foot is glued to the floor and you're trying to kick the wall behind you as hard as you can.”
If this latter technique gives you better and longer-lasting results, this may be your best course of action.
There are numerous reasons why someone could feel stiff in their hip flexors. Sometimes the answer lies in stretching the anterior hip and sometimes it’s in improving joint control by strengthening opposing muscles, like the glutes. One question to always ask is: “If I have been stretching an area that feels stiff but am not seeing lasting change, is stretching the solution?”
In practice, I rarely see a shortened psoas. More commonly the rectus femoris or tensor fascia latae is restricted. As a yoga teacher and licensed massage therapist I have come to accept that I don’t have to have all the answers but that it is helpful to be mindful with my language. I avoid using the word “tight” when talking to students and clients and prefer terms like “restricted.” To me, “tight” is an experience that cannot be quantified. For most people, this experience of “tight” triggers a reflex to either stretch or rub the area in question. However, stretching what feels tight without first assessing can perpetuate a never-ending cycle.
Instead of offering “hip-opening” sequences, I say “hip-stimulating” or “hip-centered,” because my sequences incorporate stability as well as lengthening. I regularly offer passive stretches of two minutes and longer, but I always follow them up with the kind of isometric contractions I described earlier. Isometric contractions are typically safe because they don’t inflame tissue; they can also make increases in range of motion last longer because they essentially demonstrate to your brain and nervous system that you are able to contract the muscles at both sides of, in this case, the hip joint—signaling stability to the brain, which is first and foremost concerned with survival and safety.
I believe that we yoga teachers can powerfully support our students by helping them decipher what they actually feel: like distinguishing pain from discomfort, or a stretch from a compressive sensation. An example is child’s pose. In this position, many people mistake a sensation in their hip flexors for a stretch. It is not. It is an indication of some kind of joint restriction in the hip. Expanding our students’ sensorial vocabulary is one way to help them stay safe during asana.
This goes hand in hand with defining what “tight” means to you. You don’t have to agree with my interpretation of “tight,” but it won’t hurt to get clear on what it means to you. Mindful language and assessments can bridge the gap between guessing and knowing. It can also place equal value on stability and flexibility.
Photography: Andrea Killam