Friday, February 10, 2012

Injury Series: Biomechanical solutions for iliotibial band syndrome

It's been a while since we've thoroughly reviewed an injury, so today we'll be looking at another one of the "big five" most common running injuries.  We've already seen how treatment for Achilles tendonitis has been revolutionized by specific eccentric exercises to remodel damaged tendon collagen; today's topic is iliotibial band syndrome, sometimes also referred to as (erroneously, it seems) iliotibial band friction syndrome.  It is one of the most common running injuries and seems to be a problem both for recreational runners and for elites, accounting for somewhere between 8 and 10% of all injuries, depending on the study (Marti et al., Taunton et al.)  Unfortunately, it's sometimes misunderstood, and there's a good bit of evidence indicating that current treatments centered around stretching, tissue manipulation, and anti-inflammatory drugs are incomplete.  As usual, we'll go over some basic anatomy and terminology first, then delve into what the scientific literature has to say about this injury.  Like before, I'll also include some common "tricks" runners use to overcome IT band problems, but I'll make it clear what's science and what's hocus-pocus magic.

Anatomy

The iliotibial band, commonly abbreviated as the "IT band," is a long, thick band of connective tissue (most properly referred to as a thickening of the leg muscle fascia) that serves to connect many of the major hip extensors and abductors (gluteal muscles and the tensor fasciae latae muscle) to the lower leg.  More specifically, it connects to the tendons of the gluteus maximus, the main hip extensor, and the tensor fasciae latae (TFL—a short, straplike muscle that runs between the top of your pelvis and your femur), a hip stabilizer and abductor, to the top of the tibia, just below the knee.  As such, it also helps stabilize and control the knee joint in addition to the hip.  Most relevant for runners, it seems to stabilize the hip and knee at footstrike.

As you can see to the right, the IT band runs parallel to the quadriceps muscles and hamstrings.  The black arrow points to the most common location of pain: the outside of the knee, just above the knee joint.  However, this is not the only location of pain: sometimes ITBS can manifest itself higher up on the band, along the thigh or even near the greater trochantor of the femur.  Regardless, the vast majority of ITBS cases involve significant pain on the lateral knee.

This location was widely assumed to be irritated by a small bony protrusion on the femur, called the lateral femoral epicondyle, illustrated to the left.  The lateral epicondyle is fairly easy to feel by hand, and indeed the IT band appears to slide across the epicondyle during knee flexion.  IT band pain is usually worse when the knee is at approximately 20-30 degrees of flexion, adding to the theory that the cause of IT band pain is friction between the IT band and the lateral femoral epicondyle—hence the name "iliotibial band friction syndrome."  However, recent research, MRI imaging, and cadaver studies have called this assumption into question: in 2006 and again in 2007, Fairclouth et al. demonstrate rather convincingly that, as the IT band is really no more than a thickening of the fascia latae, which envelopes the entire musculature of the lateral leg and indeed is firmly attached to the femur near the epicondyle by thick, fiberous issue; it is not anatomically possible for the IT band to "slide" over the epicondyle as if it were a "free" structure like a tendon or ligament.  But why is the IT band usually irritated over the lateral epicondyle, and why do patients sometimes respond to cortisone injections in the area? Fairclouth et al. propose that the tissue between the lateral epicondyle, which is comprised of fatty tissue rich in blood vessels and nerve endings, gets compressed by the IT band during running, particularly when the knee is at 20-30 degrees of flexion.  While this is interesting in an academic sense, does it really matter to a runner who's got IT band problems?

Interestingly, it may: the distinction between compression instead of friction of the fatty tissue between the IT band and the bony protrusion on the femur may hold the key to its origins.  If it was merely a friction issue, it seems that the solution would be fairly mundane: ice, rest, lower volume in training.  But some interesting research in the last decade or so has elucidated an interesting possibility: the nerve endings in the fatty tissue between the IT band and the femur, called Pacinian corpuscles, function as proprioceptive feedback units, giving the brain information about what's going in in and around the body.  This will become important when we return to the biomechanical origins of IT band problems, so don't forget about this fatty tissue and the nerve endings within!