How well do you understand stance phase mechanics?

Here is a recent question we fielded and thought it would make a great post. 

Question/Comment: I’m slightly confused about closed chain hip motion in the stance leg.

Maybe if I explain what my thought process is you can correct me.  Lets use
left stance phase with the right leg swinging through.

After right mid-swing, the pelvis will be rotating towards the left.  The
motion of the pelvis on the left femur would be relative femur internal
rotation.  I understand that the right leg is externally rotating
(supinating) and that normal open chain kinematics of hip extension is
coupled with external rotation.  But if the pelvis is moving towards the
left AND the left femur externally rotates, wouldn’t that create too much
rotation?  So what I’m saying is that a pelvis that is oriented to the left
with a left femur that externally rotates creates an odd motion in my head
(which may be where the problem lies).  If you’ve ever seen a western where
the gun slingers do that weird walk to a shoot out…that’s what an
externally rotating femur during terminal stance looks like to me.

I’ve discussed this with other clinicians.  Some are in agreement with me,
some think it’s externally rotating, and some don’t know what I’m talking
about.  In my patients I also see a loss of hip IR more than hip ER.  These
patients that lose hip IR seem to have more difficulty in terminal
stance/toe-off phase more than the ones that lose hip ER.

If you could help me understand these kinematics and clear this up for me I
would greatly appreciate it.

Thank you, A

our reply: 

Taking your example with the L leg in stance:
When the L heel contacts the ground, the friction of the ground (hopefully) slow the calcaneus and the talus slide anteriorly on the calcaneus. 

Because of the shape of the calcaneal facets, the talus plantar flexes, adducts and everts. This sets the stage for pronation to occur: the calcaneus everts and the lower leg internally rotates, with the thigh following. The right side of the pelvis is moving to the L (counter clockwise rotation). This should occur (ideally) until midstance. At midstance, the opposite ® foot begins to enter swing phase; this should initiate supination of the stance phase leg (L). At this point, the L foot should be beginning to supinate the the leg and thigh beginning external rotation. It (thigh and leg) should reach maximal external rotation at toe off (maximal counter clockwise rotation of the pelvis) and remain in external rotation until heel strike/initial contact on the L side again. At this point, the pelvis begins clockwise rotation.

It is necessary for the thigh and leg to externally rotate while the pelvis is rotating counter clockwise, because of the constraints of the iliofemoral, pubeofemoral and ishiofemoal ligaments.

We too often see a loss of internal rotation of the hip in symptomatic populations more often than external rotation.

We hope this clarifies things for you.

Thank you again for the question and taking the time to write.

The Gait Guys