June 2014 Archives

A Discussion Of Psoas Muscle on Yoga International

On the Massage Forum on Facebook, a Group Member posted a link to an article on Yoga International discussing the psoas muscle. I had some comments on it.

QUOTE From Article on Psoas in Yoga International at:


A tight psoas can cause serious postural problems: when you stand up, it pulls the low back vertebrae forward and down toward the femur, often resulting in lordosis (overarching in the lumbar spine), which is a common cause of low back pain and stiffness; …"

This is, in my mind, one of the great Myth-Conceptions of Psoas muscle. Because it crosses the hip joint, it certainly does flex the hip joint, and draws the femur upward, and/or the spine downward. And most theorists assume that action tilts the pelvis forward (because all other things neutral or equal, hip flexion would by definition be an anterior pelvic tilt). And it's further assumed that anterior tilt of the pelvis also causes increased lordosis.
Now, take a look at the illustration below. (You'll have to click on it to make it bigger):

psoas muscle & lumbar attachments

Three Layers of Psoas and their affect on the lumbar spine & discs

Notice that the fibers of psoas are running almost vertical as they cross the vertebral bodies. When psoas contracts, it will pull almost straight downward, and only a little forward, on the vertebrae. Can you see how that will actually compress the vertebral stack, and compress or eventually crush the discs? That action is the OPPOSITE of lordosis. It is a kyphosis or flattening of the lumbar curve.

Also note this part of psoas has two layers. The anterior layer (blue) attaches to the vertebral bodies, and the posterior layer (red) attaches at the transverse processes. … Compression, distortion & facet syndrome anyone?

Looking deeper, literally, you'll see the green layer of psoas (well, it's not really green, at least I don't think so) — called the pars vertebralis — which is illustrated almost nowhere. Only place I've seen it is John Zahourek's Atlas of Anatomy. (He was the Anatomiken Guy, the 30 or so inch human anatomy models and clay making tools so we could learn anatomy better by making each muscle out of clay and putting it in its correct location. Jon retired from the company though.)Anyway, the pars vertebralis layer ONLY crosses the vertebral bodies, and does not travel down past L-5. It's only function is to draw the vertebral bodies together. (Well, there's another, which I'll get to below.)

NOW, when someone asks you why their discs are thinning or degenerating, or getting crushed, instead of saying "OH, you're just getting old," you can give them a REAL answer: their psoas has chronically over-shortened too much.I should also say all layers of psoas can work to restrict or control extension. So if a person is doing a deep, standing back bend, then psoas will eccentrically contract (gradually lengthen) to prevent the lumbar spine from traveling too far, too fast.OK, next, you can also see how the L-5/Sacral angle is so steep, the L-5 WILL be pulled forward and down, sliding L-5 forward off the angle of the sacrum. That's part of what creates the compressing & shearing action at L-5 / S-1 that is so common.At this point, depending on what else has been going on, the Client MIGHT have what I call a "pseudo-lordosis." But rather than a true lordosis, it is more like a "kinking" action at the posterior face of the L-5 / S-1 area, and sometimes including L-4. So when you look at someone, you might sees scoop in their lower back. But as far as actual lordosis goes, it is mostly, or totally, an illusion. Like the X-ray Dr. Koplen has in a different article here on the forum, if you draw a line through the center of the lumbar, it's a pretty straight line from T-12 to L-3. That means less lordosis, not more.


Pseudo-Lordosis & Lumbo Sacral Kink

(And you have to be very careful: many people have a big, deep scoop in their lower back REGION. But if you palpate their actual spine (spinous processes), their lumbar curve is either normal or they have a loss of curve in the actual vertebrae themselves. I've had one deeply curved there actually have a lumbar vertebrae actually slightly protruding posteriorly! She was under a HUGE amount of compression. 

This assessment error leads to a LOT of mis-evaluation of structure. I've had dozens of therapists in my trainings who were told by some guru somewhere they were an example of anterior tilt and excess lordosis. It did not take long for the class to see that was not true AT ALL. In other cases, they were pretty close to neutral.)

Now, the tricky question. Does the pelvis tilt anterior because of the lower part of psoas crossing the hip joint? Or does the pelvis tilt posterior (tucking under) because of the part crossing the lumbar spine? I'm tempted to say that they tend to cancel each other out and just compress everything right along the center line through the vertebrae and hip joint.

However, if the person is standing upright in gravity, their femur is much less likely to move much (meaning the psoas cannot lift their femur, unless they are going to stand on one leg, but in that case they are FAR more likely to posterior tilt anyway to stabilize against gravity). And the lumbar region will be freer to move because it is not holding the weight of the body or being stabilized by gravity as much. 

So my vote is it's more likely to go into posterior pelvic tilt. Please let me know what you think about all that.

On the other hand, a weak and overstretched psoas can contribute to a common postural problem in which the pelvis is pushed forward of the chest and knees."

I know this is blasphemy, but I do not consider psoas to be much of a postural muscle when just standing upright in gravity without extra weight or external forces. As mentioned above, psoas has better things to do than stabilize the spine unless you're doing some special movements or exerting or resting outside forces. (I don't buy the usual tent-pole model too much. And there are other muscles better positioned to do that postural stabilization job anyway.) 

Yes, psoas does eventually get recruited as such due to bad body mechanics and bad relationship to gravity. But there are so many other muscles that are hip & lumbar flexors, I doubt having an over-stretched psoas, by itself, would create the pushed forward pelvis very much, if at all. The other ones, like iliacus, adductor longus & brevis, pectineus, and rectus abdominus, will hold the pelvis back. What causes the pelvis to push forward has FAR more to do with over-shortened hip extensors: hamstrings, gluteals, and deep rotators.

OK, that's my short dissertation on Psoas. (I also have an 80-page version, too!) Feedback, criticisms, comments welcome. If you see anything wrong with my analysis, I'm happy to hear it because I want to improve my system of analysis where ever possible.