Do you know where your rocker is?

At 1st pass, some articles may seem like a sleeper, but there can be some great clinical pearls to be had. I recently ran across one of these. It was a presentation from the  42nd annual American Academy of Orthotists and Prosthetists meeting in Orlando, March 2016 entitled “ Shifting Position of Shoe Heel Rocker Affects Ankle Mechanics During Gait”. The title caught my eye.

They looked at ankle kinematics while keeping the toe portion of rocker constant at 63% of foot length, angled at 25 degrees and shifting the base of a rockered shoe from 1cm behind the medial malleolus, directly under it and 1cm anterior to it. Knee and hip kinematics did not differ significantly, however ankle range of motion did.

The more forward the ankle rocker, the less plantarflexion but more ankle dorsiflexion at midstance. So, the question begs, why do we care? Lets explore that further…

  • Think about the “average” heel rocker in a shoe. It largely has to do with the length of the heel and heel flare (base) of the shoe. The further back this is (ie; the more “flare”) the more plantar flexion at heel strike and less ankle dorsiflexion (and thus ankle rocker, as described HERE) you will see. Since loss of ankle dorsiflexion (ie: rocker) usually means a loss of hip extension (since these 2 things should be relatively equal during gait (see here), and that combination can be responsible for a whole host of problems that we talk about here on the blog all the time. Picking a shoe with a heel rocker based further forward (having less of a flare) would stand to promote more ankle dorsiflexion.
  • Having a shoe with a greater amount of “drop” from heel to toe (ie: ramp delta) is going to have the same effect. It will move the calcaneus forward with respect to the heel of the shoe and effectively move the rocker posteriorly.
  • Lastly, look a the shape of the outsole of the shoe. The toe drop is usually clear to see, but does it have a heel rocker (see the picture above)?

These are  a few examples of what to look for in a clients shoe when examining theirs or making a recommendation, depending on whether you are trying to improve or decrease ankle rocker. We can’t think of why you would want to decrease ankle rocker, but with conditions like rigid hallux limitus, where the person has limited or no dorsiflexion of the great toe, you may want to employ a rockered sole shoe. We would recommend one with the rocker set more forward.

What’s up, Doc?

Nothing like a little Monday morning brain stretching and a little Pedograph action.

This person had 2nd metatarsal head pain on the left. Can you figure out why?

Let’s start at the rear foot:

  • limited calcaneal eversion (pronation) L > R. The teardrop shape is more rounded on the left. This indicates some rigidity here.
  • note the increased pressure at the  medial calcaneal facets on each side with the increased printing
  • very little fat pad displacement overall

Now let’s look at the mid foot:

  • decreased mid foot pronation on the L. See how thin the line is going from the rear foot to the forefoot along the lateral column? This indicates a high lateral longitudinal arch

Now how about the fore foot?

  • increased printing under the met heads bilaterally; L » R
  • increased printing of 1st met head L » R
  • increased printing at medial proximal phalynx of hallux  L » R
  • increased printing of distal phalanges of all toes L » R

 Figure it out?

What would cause increased supination on the L?

  • short leg on L
  • more rigid foot on L
  • increased pronation on the R

Did you notice the elongated 2nd metatarsals (ie: Morton’s toe) on each foot?

Here is what is going on:

  • there is no appreciable leg length deformity, functional or anatomical
  • The Left foot is more rigid than the Right, thus less rear, mid and fore foot pronation, thus it is in relative supination compared to the right foot

do this: stand and make your L foot more rigid than the right; take a step forward with your right foot, what do you notice?

  • Can you feel how when your foot is supinated
  • can you see how difficult it is to have ankle rocker at this point? remember: supination is plantar flexion, inversion and adduction
  • Can you feel the weight of the body shift to the outside of the foot and your toes curl to make the foot more stable, so you do not tip to the left?
  • now, how are you going to get your center of mass forward from here? You need to press off from your big toe (hallux)

Wow, does that make sense now?

What’s the fix?

  • create a more supple foot with manipulation, massage, muscle work
  • increase ankle rocker by training the anterior compartment (shuffle walks, lift/spread/reach exercise, heel walking, Texas walk exercise, etc)
  • have them walk with their toes slightly elevated
  • we are sure you can think of more ways as well!

The Gait Guys. Increasing your gait literacy with each and every post. If you liked this post, tell others and spread the word. If you didn’t like this post, tell us! We value your constructive feedback.

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Forefoot Rocker and Premature Heel Rise:

 

Remember the rockers? We did a series on this a few weeks ago. Remember there are three: heel, ankle and forefoot. We are going to concentrate on the forefoot today. As a reminder, forefoot rocker occurs at the 1st metatarsal phalangeal joint (big toe knuckle) as the tibia progresses over the forefoot during forward movement. There are 4 things that SHOULD happen at this point to ensure the heel comes up :

 

1. continued forward momentum  of the body

2. the posterior compartment (primarily the gastroc/soleus group and tibilais posterior) contract to accelerate the rate of forward limb movement.

3. passive tension in the posterior compartment muscles

 the windlass effect of the plantar fascia (see diagram)

Watch this slow motion video and what do you see? You should see some midfoot collapse and premature heel rise, especially on the right foot. Did you notice the little “bounce” in his step? How about the subtle adduction of his heel, L > R?  Watch it again until you see it. (The bounce is generated by the premature heel lift and premature firing of the calf compartment muscles.  Normally the body mass is further forward of the heel rise event, and thus contraction of the calf generates a more forward directed vector, however, when the heel rise is premature the body mass is still somewhat over the foot.  Thus, if the calf were to fire at this moment, it would cause a vertical body mass movement vector.  When this occurs bilaterally these clients will have a very “bouncy” vertically oriented gait strategy.  This is very inefficient gait when it occurs. Plus there is a dramatic reduction in the pronation phase of gait, so shock absorption is severely reduced.)

Does he have forward progression of the body mass? Yes

Do you think the posterior compartment is actively contracting? Probably too much. Remember the medial gastrocnemius adducts the heel at the end of terminal stance to assist in supination.

Does there appear to be increased passive tension in the posterior compartment? Yes, it appears to be the case !

How is his windlass mechanism? Good but not good enough. (see our next blog post regarding the Windlass)

Premature heel rise… Coming to a midfoot overpronator and people with loss of hip extension near you.

Telling it like it is. We are the Gait guys…..

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Gait Cycle Basics: Part 3

As Promised: The Rockers…

According to Perry, progression of gait over the supporting foot depends on 3 functional rockers

heel rocker: the heel is the fulcrum as the foot rolls into plantar flexion. The pretibial muscles eccentrically contract to decelerate the foot drop and pull the tibia forward

 

ankle rocker: the ankle is the fulcrum and the tibia rolls forward due to forward momentum. The soleus eccentrically contracts to decelerate the forward progression of the tibia over the talus. Ankle and forefoot rocker can be compromised by imbalances in strength and length of the gastroc/soleus group and anterior compartment muscles.

 

forefoot rocker: tibial progression continues and the gastroc/soleus groups contract to decelerate the rate of forward limb movement. This, along with forward momentum, passive tension in the posterior compartment muscles, active contraction of the posterior compartment and windlass effect of the plantar fascia results in heel lift.

Now see if you can pick out the rockers in today’s video.

The Gait Guys… We are everywhere!!