Running along the length of both your thigh bones is a section of tissue so universally reviled, so poorly understood and deeply mistrusted, you’d think it was a presidential candidate. If your body was the set of a loveable comedy sitcom, this would be that one character who is “the worst:” It’s the Jerry Gergich of human anatomy.
It’s called your Iliotibial band—IT band for short—and the only reason most people have ever heard of it is because its name features prominently in the well-known and much-maligned IT Band Syndrome, a diagnosis so frustrating I ought to add a trigger warning before mentioning it.
Most conversations about the IT band revolve around it hurting, tightening, failing, swelling, deteriorating or, occasionally, pouring sugar in your gas tank. It’s a bad seed. Or at least, that’s its reputation on the street. I think the real problem may be that we just don’t really understand what, exactly, it does.
Let’s start with what it is. The IT band is essentially a tendon, a thick elastic cord that bridges the space between your pelvis and your shin bone. Most literature on the function of tendons reiterates two frankly baffling assertions:
First, that the role of tendon is to attach muscle to bone: this is akin to asking “who is Leonardo Di Vinci” and being told he is “a painter.” It may not be a false statement, but that doesn’t mean it’s the right answer.
The second is that tendons protect muscles by “buffering” the energy that the attached muscle must absorb as it stretches. Much like stating that a hot oven effectively prevents your biscuits from freezing, this is a technically correct statement that completely misses the point.
Consider a bow and arrow: as you pull back on the bowstring, it gradually increases in tension. When released, that tension will become kinetic energy applied to your arrow. That means the only way to build up energy for a more powerful shot is to pull your bowstring back farther and hope it doesn’t break which, eventually, yeah, it totally will.
However; attach your bowstring to something that’s stiffer than the bowstring but still a little flexible—say a quality shaft of Madagascar Rosewood—and something pretty cool happens: as the bowstring draws farther back, its tension begins to reach an equilibrium with the stiffness of the shaft. This causes the shaft and the bowstring to bend together, collectively storing the energy applied by the pull. This is that “buffering” I was scoffing at a moment ago; indeed, the wooden shaft is protecting the bowstring from strain by absorbing some of the load, but that’s not what makes a bow a powerful weapon: it’s the fact that the shaft joins the string in storing energy which will eventually be released into the arrow.
What’s more, because of the variation between the stiffness of the bowstring and the shaft, the arrow will receive the kinetic energy from each at different times, prolonging the overall time wherein the arrow is accelerating. Longer acceleration means a faster, fiercer arrow.
Tendons don’t “stabilize” or “buffer,” or simply connect muscle to bone: they’re the Madagascar Redwood of your joints; they’re how the power that moves you moves.
In many ways, it makes more sense to think of muscles as being extensions of their tendons, rather than the other way around. Tendon provides powerful elastic return—93% of the work applied to stretching it—but it can’t be directly controlled by the brain. A muscle is essentially the “cockpit” of the tendon, receiving orders from the nervous system to contract strategically so as to maximize its tendon’s impressive energy return. This is especially true for the IT band, which dwarfs the muscle to which it is linked: the tensor fascia latae, or TFL.
The IT band also boasts a unique geometry that grants it the ability to facilitate flexion in both of the joints it crosses—the knee and the hip—simultaneously; most of the two-joint tissues in the lower limb typically flex one of their constituent joints while extending the other. Put another way, this means that both ends of the IT band are either shortening or lengthening at the same time, and this provides us with a fascinating clue into it’s role in the body.
See, most of the energy you produce when your foot strikes the floor transfers directly to your center of mass as propulsion, literally moving you forward. However, some of that energy needs to be saved; the leg behind you has to get back in front somehow, right? Otherwise you’d get in two very powerful strides before collapsing into a useless heap. The IT band is the body’s method of doing exactly that: siphoning off some of the energy from stride and releasing it at just the right moment to fling the leg back forward in front of the body so that it can strike the ground and do it all again. Kinda like this:
With a single elastic tissue and the assumed forces of gravity and friction, the whole leg can reset from terminal stance to initial contact. That’s what your IT band does, and it’s freaking beautiful.
Additionally, this gives us powerful insight into how to treat a dysfunctional IT band. What we clearly see in the model above is that the IT band is dependant on—and instrumental in generating—cooperation between the hip and knee joints. In order to make the transition from terminal stance to loading response phase, the knee and hip must flex in concert, and with very specific timing. When the IT band shows signs of distress, it’s a solid bet that the hip/knee timing is off. What’s more, how it’s off can be easily predicted by knowing if it’s the dominant or the non-dominant side that is behaving dysfunctionally: If the dominant side is in distress, the hip is flexing too fast, and the knee too slow. For the non-dominant side, it’s the reverse. You would be amazed at the number of IT band Syndrome cases I’ve seen get better with little more than the deceptively simple cue: “bend your knee more.”
If you’d like to know more about these side-dominance predictions, you’ll have to wait for the next blog OR attend one of my many upcoming workshops!
Feel free to leave any questions in the comments!