Just what is functional hallux limitus?

Just what is functional hallux limitus? This has been occupying my mind too much since I posted this and recorded the Clinical Biomechanics Boot Camp video on functional hallux limitus.

I think we all agree on the definition of what functional hallux limitus is. It is that situation in which there is a full range of motion at the first metatarsophalangeal joint during non-weightbearing, but during gait the joint (for whatever reason) just does not want to dorsiflex.

Part of the controversy surrounding functional hallux limitus is the “for whatever reason” and I probably contributed to the controversy with our sensitivity study which is amazing how many different people twist for their purposes! Part of the reason we found what we found is that if functional hallux limitus really does exist, then it probably exists on a continuum and not as an either/or (which is what our study classified the feet as).

But, just what is it. It could be:
1. Idiopathic. This would be a ‘primary functional hallux limitus’ that is a true entity and is not due to any of the reasons below.
2. ‘Secondary functional hallux limitus’. This would be due to anything that is preventing first ray plantarflexion (eg ‘overpronation’; medial orthotic posting; midfoot collapse etc); ie the restriction on first MPJ dorsiflexion is secondary to something and not a primary problem as in (1) above.
3. High force to get the windlass established. When weightbearing and you try to dorsiflex the hallux, some feet are just really hard to dorsiflex due to the forces associated with the windlass. In some places this is taught as a test for functional hallux limitus. It’s a test of the first MPJ dorsiflexion stiffness, of which most of it is due to the windlass. I have never considered it a test for functional hallux limitus (will get into that one another day)
4. A delay in the windlass. When you get someone standing and start to dorsiflex the hallux, the arch, via the windlass, can raise immediately; in others there can be quite a delay in the arch raising and up to >10 or so or more degrees of dorsiflexion occurs before the first ray plantarflexes and windlass works (is probably the same as (2) above)
5. The post from last week talked about the failure to integrate the foot tendon guard reflex, which would prevent first ray plantarflexion (is probably the same as (2) above)
6. For those familiar with the ‘split second effect’ theory or concept in those with tight calf muscles and look at all the pictures of that concept. All the pictures used to illustrate that concept all look the same as the pictures used to illustrate functional hallux limitus! (go figure that one out!) So is it due to equinus?
7. Or is it caused by a tenodesis effect at the retrotalar pulley (see this thread)

Question: is there such a thing as idiopathic functional hallux limitus, after all the possible causes in 2-7 above are ruled out?


All the threads on functional hallux limitus