Passive dorsiflexion and plantar flexion?

[Lothric]

Hey,

I don't understand the mechanism behind passive dorsiflexion and plantar flexion at all. I can read that "In passive dorsiflexion in the anke joint, the muscles ventrally of the axis of movement will relax and those dorsally of the axis will contract".

That does not make any sense. If tibialis anterior relaxes (ventrally), then gastrocnemius (dorsally) will contract? That would give a plantar flexion and not a dorsiflexion.

I'm seriously confused.

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[donovank730]

It helps to understand what the dorsal surface of something is. Dorsal fin on a fish is on its back so that always helps me remember.

Starting from there, dorsifelxion, is flexion of the dorsal surface of the foot, so the top of your foot is coming closer to your shin, and your tibalis anterior is going to contract to provide this movement

Plater flexion is the exact opposite. The plantar surface is the side that plants you on the ground, and where you get Plantar Fasciitis, so this side is flexing and trying to close the angle with the ground( or think of it as your toes trying to get closer to the heel of your foot.)

Use this logic and than follow what muscles must contract for these movements, it should be simple.

 

[Lothric]

That logic I understand completely, but I still can not see how "The muscles ventrally of the axis of movement will relax" and "those dorsally of the axis will contract" will work. Isn't tibialis anterior ventrally of the axis? If tibialis anterior does not contract and the muscles dorsally of the axis (like triceps surae) contract, how is this going to give rise to a passive dorsiflexion? It should be a plantar flexion as triceps surae plantar flexes the ankle...

Maybe I just don't understand what ventrally and dorsally of the axis of movement means in this case...

Help!

 

[donovank730]

I think your problem is that whatever resource your reading is horrible. Keep it simple and don't overthink it. The posterior calf muscles cause plantar flexion and the anterior ones cause dorsiflexion. Thats all you need to know unless you want to get out a goniometer and draw some force vectors(plz don't do that)

Couple this with an understanding of what nerves are involved in each process and you know everything you need to know about this subject

 

[Lothric]

Hmm,

Is this one of those scenarios where you have to think about balance? Kind of how there is a balance between the extrinsic flexors and extensors of the hand, as well as the intrinsic muscles of the hand.

So in this particular case, the posterior calf muscles cause plantar flexion --> anterior side with tibialis anterior tries to counter that by contracting to achieve balance?

Sorry if this is still not the case. I'm literally dragging my a*s at this point with alot of things going on in life atm.

 

[Lothric]

bump

 

[Reperfused]

Tibialis anterior is dorsal.

 

[Lothric]

Tibialis anterior is dorsal.

What do you mean by that? Anatomically, it is anterior. Or are you refering to the axis of movement? I get really confused when thinking in terms of axes of movement.

So I am wrong when it comes to the balance? If muscles dorsally/posteriorly contract (triceps surae would cause plantar flexion), this will stretch the anterior muscles --> passive dorsiflexion (tibialis anterior) due to stretch reflex?

 

[Reperfused]

In the lower extremities, anterior is dorsal and posterior is ventral.

 

[Lothric]

In the lower extremities, anterior is dorsal and posterior is ventral.

Oh wow, must be due to the embryology then huh?

Well, then it makes sense that the dorsal muscles contract and cause dorsiflexion.

But how does "passive" dorsiflexion work, exactly? I don't think I get the principle. I can't find anything about in in Google either. Is it as simple as "When one muscle dorsally (anterior of the lower limb) contracts, the other muscles dorsally (anteriorly) will follow and contract as well." Is that how it works? So the muscles only have to be in proximal location to each other, not have the same function?