The story goes something like this:
Foot excessively pronates causing the tibia to excessively internaly rotate; when the vastus contract, the patella is then pulled lateraly relative to the femoral condyle; that maltracking causes pain, known as anterior knee pain or patellofemoral pain syndrome.
Tiberio gave a detailed description of this pathomechanical mechanism. Based on that, clinicians have widely used foot orthotics to stop the foot pronating to treat anterior knee pain. They have been doing this for a very long time with generally good results.
The problem with this model is:
1. Only one of a number of cross sectional studies have shown that there is even a correlation between foot pronation and anterior knee pain
2. None of the prospective studies show any relationship of foot pronation to anterior knee pain
3.Tibial rotations are under the control of proximal influences and not the foot (see Bellchamber and van den Bogert)
Foot orthoses to treat foot pronation in those with anterior knee pain, work. Three randomised controlled trials have shown this:
Wiener-Ogilvie et al (2004)
2) Eng & Pierrynowski (1993)
3) Collins et al (2008)
(don't let anyone tell you that foot orthoses for anterior knee pain don't work; there are three RCT's that tell us they do work and none that tell us they don't work; ask the cynics for their evidence)
So we have:
A model that is wrong; but treatments based on that model work.
No wonder critics do look cynically at the whole concept of foot orthoses for anterior knee pain in the context of this apparent paradox. Just because the model is wrong, does not mean the RCT's that used foot orthoses based on the model got it wrong.
Is there a solution to this paradox:
Any number of models may eventuate to explain this. One option is what was shown by Stefanyshyn et al. They showed in those with anterior knee pain had higher knee abduction impluses. We also know that foot orthoses do affect joint moments at the knee; so a potential model could focus on the effects of foot orthoses on knee joint kinetics and not the kinematics (ie its about the forces and NOT the motion)..
Postscript: I blogged here more about this.