Pronation coming from...

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I've been hearing this a lot recently. Sam R is often telling me he sees pronation "coming from the hips" Perhaps its a gap in my education but i admit i don't really know what this means!

Sub talar pronation takes place around the sub talar axis. How can it "come" from somewhere?

Is this another way of saying "caused by a dysfunction in"? If so how can you tell by watching someone walk that the pronation (or too be more accurate the loss of control of pronation) is caused by hips or upper body?

Do we even know what proportion of pronatory control originates from what? I'm still trying to generate the equation for that one!:deadhorse:

Any pearls of wisdom on this one would be appreciated.

Regards
Robert

 

Hi Robert,

Of course pronation at the STJ cannot come from the hips.

However, the amount of available movement at the ankle joint complex suggests (to me) that this is an excellent place for compensation for other joints which perhaps do not have a full ROM to take place.
Especially when the compensation is used to allow the foot to move into a comfortable plantigrade position against a hard, flat surface.

Regards,

David

 

Obviously what they mean is that the "pronatory moment to the subtalar joint (or whatever joint they are talking about that allow pronation) is coming from ...."

 

Will a pronatory moment originate at the hips?

I can't see how this is possible. It can originate at the foot/ground interface because of hip position.

 

Actually you probably right - it can only originate from the hip if there is a force internally rotating the hip when the foot is fixed on the ground.

 

Which leaves us three possible meaning.

1. There is an active internal rotation force occasioned by pelvic swing or muscular activity in the hips or a passive blockade to femoral external rotation (tight muscles / ligaments / joint changes) which prevent adequate rotation to allow STJ neutral

2. There is a structure in the hips which SHOULD be providing a supination moment via external rotation of the leg which is not (or not sufficiently) performing.

Number 1 is something which can be observed often in paeds. Tight internal rotators and suchlike. Thing is, they operate throughout gait including swing phase and thus cause in toeing. For this mechanism to cause pronation it would have to operate only AFTER the foot loads. Does EMG data indicate any muscle groups which would operate in this way?

Number 2 seems more likely. However i have two problems with this :-

a) So far as i can make out we have little idea just how much supinatory moment is generated by hip rotators. This being the case how can we say that this is "where it is coming from"

b) Assuming for a second that the hip rotators (or lack thereof) ARE the factor causing a pathological loss of supination moment, how is this detectable by gait analysis or other means? For eg.If the total pronation moment across the STJ at a given instant when the forces should have acheived balance is 100 Arbitary units (AUs) and the supination moment is 90 AUs how do you tell that the missing 10 AUs SHOULD be supplied by the hips? What to say it is not the case that the pronation moments are amplified by a deviated axis? Or that the missing 10 AUs are not lacking from the action of the tibialis posterior?

Regards
Robert

 

If you can stand upright, lift one foot off the ground and then forcefully internally rotate the thigh relative to the pelvis, then you can have your hip "cause" subtalar joint (STJ) pronation. An internal hip rotation moment will cause STJ pronation moments as long as the foot is weightbearing due to ground reaction force resisting internal rotation of the foot relative to the ground.

And the ground does not need to be hard and flat for this to occur!

The question is not whether the hip can cause STJ pronation since it certainly can. The question is how frequently does internal hip rotation moments become the main source of excessive magnitudes of STJ pronation moments during weightbearing activities......I believe this only occurs rarely.

 

On moments at the hip causing moments at the sub talar joint (STJ) We have to remember Newton's third law. If the trunk applies a moment to the femur then the femur applies a moment to the trunk. So, if you are standing on on leg and using your hip muscles to cause an internal rotation of the weight bearing leg, you should see the trunk accelerate in the oppoiste direction. There is a fair amount of inertia in the trunk, more than there is the lower extremity, but it is not infinate.

In gait, you may want to change the direction you are going. One way would be to use the hip muscles to change the ankle of the frontal plane of the trunk to the old line of progression. This kind of movement is probably something that could cause moments at the STJ. The question is how big is this moment compared to the moments from the muscle and the moments from ground reaction force.

Just more to think about.

Cheers,
Eric

 

Who said it did?
Not me!

 

Robert




My diagram shows GRF -Fx causing internal rotation moments about the hip at heel strike and early mid stance. The external rotators are tensioned to resist internal rotation. If the internal rotators are weak then the femur and tibia will internally rotate and more pronation may result. This will cause an excursion of -Fx to the medial foot and so increase internal rotation moments, which has a cyclical effect.

The balancing reaction force for the external rotators comes from inertial force of the trunk and right leg mass, which would tend to rotate about the right leg in a positive y axis rotation or anticlockwise looking from above.

Therefore could one view the hip as the balance point between moments from GRF and moments from body mass inertial force. Any deficiency at the hip might allow a dysfunctional gait manifesting as excessive pronation at the STJ.

Cheers Dave