Get your foot in High Gear!

image source: Foot Orthoses and Other Conservative Forms of Foot Care. Michaud 1997; Williams an Wilkins: with permission

When it comes to gait, getting the 1st ray to the ground is the name of the game. When weight travels through the medial forefoot and we are able to push off the 1st ray complex, that is called "high gear push off". This was 1st discussed F Bojsen-Møller in this excellent paper (1), that just happens to be a free full text! Craig Payne, The Running Research Junkie has offered and excellent commentary on the topic here as well.

High Gear Push Off can happen when 3 conditions are met: 

1. we have a intact visual, vestibular and kinesthetic systems that ensure we can remain upright in the gravitational plane.
2. we have an intact calcanocuboid locking mechanism
3. we have adequate skill, endurance and strength of our extensor hallucis brevis

The 1st condition is more global and ensures that our cerebellum and vestibular apparatus are playing nice together to create balance, of the literal sort, We seek to keep our visual axes parallel and our center of gravity over our foot. Remember that the BODY will move itself AROUND the visual axes. If the axes are off, the brain will tilt the head and the body will move AROUND the head to accommodate. We have talked about that in these posts here on the blog. 

The 2nd condition, the calcaneo-cuboid locking mechanism, works in the coronal plane and relies on a functioning peroneal group, where the peroneus longus and brevis wrap around the lateral malleolus, cuboid and tail of the 5th metatarsal, crossing the foot diagonally to insert on the base of the 1st metatarsal. When working properly, its actions will be to plantar flex and everting the forefoot, lowering the 1st ray complex down and assisting the shift of the center of gravity more medial for the weight to pass through the medial foot and out through the hallux (ideally). 

The 3rd condition, the ability to descend the 1st ray, relies on the actions of the peroneus, appropriate supination of the forefoot and ability of the extensor hallucis brevis to do its job.  Because the tendon travels behind the axis of rotation of the 1st metatarsal phalangeal joint, in addition to providing extension of the proximal phalynx of the hallux, it can also provide a downward moment on the distal 1st metatarsal (when properly coupled to and temporally sequenced with the flexor hallicus brevis and longus). If the axis of motion for the 1st metatarsal phalangeal joint moves posteriorly, to behind (rather than under) the joint, the plantar pressures increase at MTP’s 4-5 and decrease at the medial mid foot, moving you into low gear push off.  If moved even further posteriorly, the plantar pressures, and contact time in the mid foot and hind foot (2). For more on the extensor hallucis brevis, see our post here.

As you can see, high gear is desirable over low gear push off, but sometimes circumstances or biomechanics do not permit. High gear push off ensures the forefoot is dorsiflexed and everted with respect to the rearfoot and the calcaneocuboid and talonavicular joint axes are perpendicular to one another, giving us a rigid lever to push off of as the center of gravity moves medially across the foot. In low gear push off, the foot is inverted and plantarflexed and the stress falls on the lesser metatarsals and lateral stabilizing complex of the ankle, moving the center of gravity laterally, in addition to the calcaneocuboid and subtalar joint axes being more parallel,  creating a less rigid lever for push off and decreased mechanical efficiency.

1. Calcaneocuboid joint and stability of the longitudinal arch of the foot at high and low gear push off. J Anat. 1979 Aug; 129(Pt 1): 165–176.  link to free full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1233091/

2. van der Zwaard BC1, Vanwanseele B, Holtkamp F, van der Horst HE, Elders PJ, Menz HB Variation in the location of the shoe sole flexion point influences plantar loading patterns during gait. J Foot Ankle Res. 2014 Mar 19;7(1):20.

The Power of the 1st Ray?

Does the 1st ray complex have super powers? Perhaps Marvel should consider a new superhero “Ray”? We are not sure but here is a story that gets us one step closer to the answer. 

While teaching a course this past weekend and doing a teaching case, we examined one of the participants who had high arches, a rigid rearfoot varus, internal tibial torsion, R > L, and foot pain R>L and a dorsal exostosis (growth of extra bone from stress at the base of her 1st metatarsal) where it articulated with the  1st cunieform on the right. No surprisingly, she also had a partially compensated forefoot supinatus on the right. She had increased wear on the lateral aspect of her shoes and a walking strategy which involved hiking the right side of the pelvis during stance phase on the left, and a pelvic shift to the right during stance phase on the right, as well as an inability to get the head of either 1st ray complex to the ground, R > L. It was also determined she had, not surprisingly, locking of the 1st metatarsal cunieform joint on the right and a loss of anterior and posterior shear at the superior tib fib articulation on the right, as well as hypomobility of the right sacoiliac joint. There was weakness of the abdominal external obliques bilaterally and posterior fibers of the left gluteus medius, along with the long toe extensors on the left and short toe flexors, a pattern that we often see clinically.

We then proceeded to treat her tib posterior, peroneus longus and flexor digitorum on the right, all of which have an effect on descending the 1st ray, along with the long extensors on the right, which would effectively raise the distal aspect of the 1st ray, but we thought may provide better eccentric control of the foot from initial contact to loading response, and again from the end of terminal stance and through swing phase.  We then mobilized the 1st met cunieform articulation only. Ideally, we should have reassessed after we made EACH change, but due to time constraints, AFTER we had done ALL these things. 

Rexamination had better 1st ray motion, restoration of tib fib motion and restoration of R sided SI mechanics. Her 1st ray descended much better, tib fib motion was normalized, L sided hip hiking strategy and R sided pelvic shift were greatly improved. For the 1st time in 10 years, the participant had no foot pain. Coincidence? Perhaps. Placebo? Maybe. You decide. 

Sometimes, doing a little of the right thing can be a good thing. Sometimes we overdo. I have to admit, because I am a chiropractor, I would have started with manipulation 1st of all 3 articulations with a recheck immediately post treatment AND THEN treated the other dysfunctions. For those of you who are manual therapists, I am sure you see miraculous things happen when we cavitate joints and change their instantaneous axes of rotation. I can thank Dr Ted Carrick and my good friend and colleague, Dr Paul Chille, for teaching me that. The students, in this case, were driving the bus and I went along with it.  I was surprised (though I shouldn’t have been) to see the pathomechanics resolve WITHOUT manipulation, but it got me thinking I should consider treating the muscular dysfunctions 1st, and then recheck and manipulate later. It makes sense that the receptor density of the lower extremity musculature has a much larger population of muscle mechanoreceptors, especially in the foot, since it has a greater cortical representation than the joint mechanoreceptors.

My students never cease to teach me something new...