hello anatomy friends this is dr alsup and we are going to finish our discussion on the
joints of the lower limb and we are going to first talk about the different joints that you can find
between the tibia and the fibula and there's actually quite a wide variety there and then
we will finish with the talocrural joints and a few of the associated joints in that region
so basically what i just said there and our good friend the syndesmosis is going to make a a guest
appearance here okay so recall like what we had in the radius and the ulna there are going to be a
very similar structure associated with between the tibia and the fibula however we don't have that
rotation that occurs with pronation supination here so we don't have quite as much movement
occurring between the tibia and the fibula so you're going to have joints that are a bit
more playing a functional role in stability so you'll have three different joints though so
three different places where the tibia and the fibula will articulate so you'll have a superior
tibiofibular joint which is actually an example of a synovial plane joint
you will have the interosseus membrane of course between the bodies and the sha or the shafts of
the tibia and the fibula and then on the distal portion or its distal most articulation will be
an example of a syndesmosis so you'll have the tibiofibular syndesmosis on the distal
the distal most joint and recall that we have put that interosseus membrane as a type of
synthesmosis as well so two of the three joints are going to be fibrous rather than synovial only
the superior tibiofibular joint will be synovial and that makes sense in terms of the function like
i mentioned we do not have the rotation occurring with pronation and supination so we don't have
that radius moving over the ulna so the fibula say is not rotating over the tibia so not as much
movement more stability here so making sense that we have um less synovial joints in this region
and if we if you ever heard the term and a high ankle sprain is actually talking
about some type of disruption to the ligaments associated with the distal tibiofibular joint
so that would be a high ankle sprain so let's talk a little bit about the ankle joint or the tallow
cruel joint now we're looking at a radiograph here you can actually see there's a bit of a fracture
in terms of the lateral malaise but we're focusing more on the bones here and the bones
that are articulating to form the talocrural joint are going to be the distal parts of the fibula
the tibia so you can see the tibia is playing a big role in terms of not only
its medial portion here but this whole bottom portion and then lastly so this is tibia and
the most inferior will be the talus which is going to be that superior most tarsal bone
and these articulate to to form a hinge joint so the primary movement that
occurs here is called dorsiflexion or plantar flexion which is basically flexion and extension
with some important considerations in terms of how we describe them so dorsiflexion is going
to have that heel kind of grounding to the ground with the toes pointing up whereas plantar flexion
is going to be the heel kind of up in the air with the toes planted on the ground all
right so you have obviously you're going to have other joints that are going to play a role here
but in terms of what's occurring right at this joint you'd have either dorsiflexion or plantar
flexion and that's an important consideration is very rarely do these movements occur in a vacuum
you're going to have other joints in this general region that are also causing movements to occur
now plantar flexion is going to um well the ankle is going to be relatively unstable
during plantar flexion it is much more stable during dorsiflexion so if you
think about standing on your toes you can only do that for so long and you're already kind of
wobbly just kind of doing it from the get-go whereas with dorsiflexion that's going to be
a more powerful movement it typically you have more stability because of a better fit
in terms of where things are in the ankle joint with dorsiflexion
okay now we are looking at the ligaments associated with the talocrural joint
and really you have two sets one on the medial side and one on the lateral side and those that
are on the medial side are either referred to as the medial ligaments or when you combine them all
we can refer to these as the deltoid ligaments kind of shaped like a delta
in terms of what it appears as and these are by far the more robust and the stronger of the
two sets so all of these are going to have an attachment on the medial malleolus of the tibia
and then they will go to their different bones to kind of serve that role of protection but it's
important that at this medial malleolus the they often interweave and kind of
create this force in this region and then they kind of spread out from there
and these are going to play a role in terms of stabilizing the ankle during eversion and we'll
talk a little bit more about what that is in a moment but the it is going to stabilize during
eversion whereas the lateral ligaments are going to stabilize the ankle during inversion and so
on the lateral side and we have this fibula kind of in the way so you can't see them quite as well
but these are going to play a role in terms of um stabilizing during inversion they do all
also have an attachment to the malleolus on that side or the lateral malleolus
but they don't interweave quite as firmly as what you have with the deltoid ligaments
and so this anterior talofibular ligament or the atf is going to be the most frequently
damaged ligament associated with the ankle joint and one of the most frequently damaged
ligaments in the body so if you've heard of the term an ankle sprain that is going to be
torn fibers of a ligament and this is one of the most common areas for a sprain to occur
now let's talk a little bit about eversion and inversion so we talked about how the ankle joint
only allows plantar flexion and dorsiflexion but you have these two movements that are very
closely associated with the ankle joint and they're going to be important in terms of that
you'll have the subtalar joint which is going to be between the talus and the calcaneus right there
and then you will also have the transverse tarsal joints which is going to be kind of between the
calcaneus and the talus and the navicular and the cuboid here and these will allow for
what's referred to as eversion and inversion you can think of inversion kind of as making
the soul of your foot face medially so this would be medial and eversion would be making the sole
of the foot face laterally and so try to invert and evert your own foot which one can you which
one do you have a greater range of motion of it's likely that you probably have a greater
range of motion in terms of inversion and that has a lot to do with the fact
that these lateral ligaments are the ones that are stabilizing the ankle during inversion there's a
bit more flexibility here than what you have for the deltoid ligaments which will stabilize
the ankle during eversion so you cannot evert the foot quite as much as you can as inversion
so that talocrural or ankle joint is going to be one of the most frequently injured of
the major joints of the body again ankle sprains are kind of the the most common of those injuries
and these are nearly almost always over inversion injuries what will often happen is that a foot
will kind of get planted and it will cause an over inversion to occur causing four some of those
lateral ligaments to tear either tear slightly they could completely be ruptured in certain cases
dependent on the severity of the sprain so think of a person stepping on an uneven surface and that
foot is very force forcibly inverted and so you can see with the different degrees of a sprain
how serious that can be now is it always an over inversion injury absolutely not it can be
any type of injury in this region it could affect the deltoid ligaments as well
these are just the most common okay excellent all right so just a real quick review here because
sometimes i think this gets lost a little bit the talocrural joint or your ankle joint is
capable of planter and dorsiflexion what type of synovial joint is it is it a ball and socket joint
a condyloid a hinge a plane or a saddle joint and so don't get lost in these two terms right here
we gotta also understand what type of joint this is so plantar and dorsiflexion
are really just the ankle specific terms for flexion and extension
so flexion and extension and only flexion extension would be a hinge joint so the
talocrural joint is a hinge joint is it true that e-version and inversion play a role
associated with the ankle joint very commonly things like plantar flexion or inversion can occur
together but they do occur at different joints of that actual movement they often
occur in unison but only planter and dorsiflexion are allowed at the true talocrural or ankle joint
excellent thank you so much for this we are going to move on to the muscles of the lower limb and
then we will move into specifics of the laboratory thank you so much for your time and attention here
always feel free to reach out with any questions and i hope you have a great rest of your day