Happy Thursday, everyone. This is Dr. Scott Gray and welcomes you to the next episode of the Redefining Physical Therapy podcast.
And so today I want to talk a little bit more about the rearfoot and foot mechanics in particular to gate.
I think this is something that is neglected and I think even seasoned clinicians just don’t really understand.
I think we also need to just kind of take a step back and understand that it’s okay for your foot to go through pronation. It should go through pronation.
And likewise, it should also go back through supination. So it’s this loading and unloading into these motions that we’re really trying to get in regards to the rear foot and midfoot.
And when the load you’re not loading into pronation at the right time or too much, that’s when it becomes pathological, same thing goes with supination. I can stay in supination too long, not enough or too much.
That can be abnormal as well, too.
So we’re going to kind of explain it just in regards to the gate, but I think let’s this backup and kind of understand what the real function of the rearfoot and midfoot is.
And so the subtalar joint goes through pronation, and when it does that, it does a couple of things.
So it allows the foot to unlock. So it allows that midtarsal joint to unlock so the foot can get flat and absorb forces.
You don’t want to land on a foot that is potentially really rigid because it doesn’t have great shot absorption. So think of it kind of like a spring or shock.
It’s going to absorb all that energy from your mass momentum and gravity and all that good stuff.
But then from here, it’s going to also do torque conversion.
So when the rear foot goes into that U version, you’re going to get tibial turn rotation up the chain for more internal rotation.
So that’s really important.
Now conversely, when I step through in gait, the rear foot should supinate, and so that’s going to create this rigid lever for me to propel off of.
It’s going to allow my forefoot to rotate into pronation so I can get a propel off my hallux and clear big toe extension. So there’s a lot of good things that can happen within that rear foot going into supination.
So also start from the top here, what the mechanics are. So when I step in gait and in my prior podcast, I talked about how the subtalar joint does not evert the heel.
So it’s actually ground reaction forces, mass, and momentum. And that’s something I learned from Gary Gray that’s going to evert the foot.
So when I go, I land at heel strike, I’m relatively supinated. But then as soon as I get my forefoot down and put some weight on it, then momentum and those great things are going to start to evert the heel.
And then that’s going to unlock the midtarsal joint. So the talus is going to go down in, the calcaneus is going to abduct and evert out to the side.
And then relative to the talus, the midfoot is going to go through abduction, but it’s also going to go through some inversion as well. So there’s an opposite correlation.
So whatever the talus is doing, the midtarsal joint forefoot is doing the opposite during that loading response.
Now, conversely, as I step through in supination, as I step through my rear foot is going to go into supination.
So my calcaneus is going to go into inversion and my talus then should go laterally. And so that’s going to then cause again at the midtarsal joint and the forefoot to do the opposite.
It’s going to deduct, and then invert or evert or pronate.
This is what we call a twist. So it’s the opposite motions. And so that’s important because again, if my foot is supinating and then if I can’t get the opposite motion of pronation at the midfoot and forefoot, then my big toe is never going to stay on the ground and I’m never going to get through that hallux as I propel off, or I’m going to get abnormal mechanics.
So in a nutshell, remember your rear foot is to cause shock absorption.
It’s also to create torque conversion, so it’s going to create rotation, our body loves rotation.
Similarly, as I then supinate, I’m going to create a rigid lever to propel off of, so that I could produce the most force.
So knowing these mechanics is really important because it’s going to help you learn how to assess and treat this foot.
And so I’ll just give you a little bit of an insight. If I step forward in gait, I want to see can that foot ever?
Similarly, as I step through in gait, can that foot invertor supinate? And keep it super simple. And if it can’t, then you’re looking at potentially a joint dysfunction.
You’re also looking at potential foot type issues where it’s structural. So they may need a foot orthotic of some sort. In regards to supination, if they can’t supinate, it could be a couple of different things.
It could be they’re not getting enough adequate ankle dorsiflexion in terminal stance. It could also be they don’t have enough strength in that calf.
Again, it could be a foot condition issue where what they have is a failed foot from some different type of foot types and then need an orthotic.
So the list goes on and on and on, but in a nutshell, there you have it. That is the foot mechanics explained for the rearfoot and midfoot.