So you think you are an iliotibial band syndrome guru ?  This study has some interesting provoking thoughts about the mechanics we have all previously assumed. It is good to challenge established teachings, for it is only through interrogating old ways that we may see the true light of things.
The iliotibial band (ITB) syndrome is a common overuse injury that is commonly misunderstood. It has been regarded as a friction syndrome where the ITB rubs against he lateral femoral epicondyle because of its previously assumed variable function, below 30 degrees knee extension it has been though to act as an extensor of the knee, and above 30 degrees (ie more knee flexion) it has been thought to act as flexor.  It is thought to be a culprit (with the biceps femoris) of the shift phenomenon in the “pivot shift test” for posterolateral rotatory instability of the knee (PLRI).  Here is an interesting perspective from a 2006 journal article.
“In all cadavers, the ITB was anchored to the distal femur by fibrous strands, associated with a layer of richly innervated and vascularized fat. In no cadaver, volunteer or patient was a bursa seen. The MR scans showed that the ITB was compressed against the epicondyle at 30° of knee flexion as a consequence of tibial internal rotation, but moved laterally in extension. MR signal changes in the patients with ITB syndrome were present in the region occupied by fat, deep to the ITB. The ITB is prevented from rolling over the epicondyle by its femoral anchorage and because it is a part of the fascia lata. We suggest that it creates the illusion of movement, because of changing tension in its anterior and posterior fibres during knee flexion. Thus, on anatomical grounds, ITB overuse injuries may be more likely to be associated with fat compression beneath the tract, rather than with repetitive friction as the knee flexes and extends.”
We found this article interesting because it challenges many thoughts about its actual movement, (“it creates an illusion of movement”) because of changing of tension in the anterior and posterior fibres. As this article suggests, it is unlikely that there is any forward and backward motion of the band over the epicondyle during flexion and extension, rather the illusion of movement is from a gradual shifting of load to and from the anterior and posterior fiber bundles during flexion/extension. It is also an interesting article to us because it suggests and challenges that the clinical phenomenon is associated with fat compression rather than friction over the epicondyle.  The authors go into discussion of how the fat beneath the distal ITBand at the knee level is well vascularized and that Pacinian corpuscles can be present in adipose tissue supporting the view that fat compression may have a proprioceptive role and a roll in pain production when the corpuscles undergo hypertrophy in such a clinical setting.
Just remember what we have been saying all along when treating what you think are lateral chain problems, the ITBand receives most of the tendon of the gluteus maximus so do not forget to examine the hip and pelvis function, but so not forget the critical contribution that impaired foot and ankle function can have proximally at the knee.
This study has some interesting provoking thoughts about the mechanics we have all previously assumed. It is good to challenge established teachings, for it is only through interrogating old ways that we may see the true light of things.
If you are looking for more of our thoughts on this topic, we discussed a clinical case in our last podcast (link here). 
Shawn and Ivo, 
the gait guys
Fairclough J, Hayashi K, Toumi H, et al. The functional anatomy of the iliotibial band during flexion and extension of the knee: implications for understanding iliotibial band syndrome. Journal of Anatomy 2006;208(3):309-316. doi:10.1111/j.1469-7580.2006.00531.x

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