hello anatomy colleagues this is dr alsup and we are going to get into the knee or the joints
of the lower limb which we're starting with the two largest ones these will be the hip
joint and the knee joint so and we will get through uh some of the uh some of the things
that we come to know about joints so what are the bony parts what type of joint is it what types of
movements are allowed and of course some of the clinical correlations and ligaments associated
so let's start with the hip joint the hip as you probably already knew this is going to be the
connection between the lower limb and the pelvic girdle and recall that pelvic girdle is going to
have an attachment to the vertebral column so a bit more stability associated with the hip joint
and not only is there this stability the stability is over a wide range of movements which is really
impressive in terms of its size next but also next to the shoulder joint is actually the
most movable of all joints so it's one of those oddities in the fact that there is quite a bit of
movements that are allowed at this particular type of joint but also a very stable joint
usually when you have less stability you have more mobility and vice versa the hip joint is
kind of one of the exceptions to the rule this is going to be formed by the head of the femur
which is comparatively larger than what you had in the humerus but what's really quite different
is the depth of the acetabulum of the coxal bones and recall that acetabulums formed
by the fusion of those three bony parts the ilium the ischium and the pubis additionally
you'll also have a fibrocartilaginous lip or a labrum and you have two often that are going
to be associated with this this is a ball and socket joint after all so you will have a labrum
or a labra associated with this to allow for a better fit there so you have these means of
stability just kind of built into how it is built so you have this really good fit between the bones
you have the labra that's going to allow for an even better fit you have the strength of the
joint capsule as well as the ligament some of the strongest most robust ligaments in the body and
then you'll have attachments of muscles crossing the joints so a very stable joint that's capable
of all types of movements that can occur at a ball and socket joint so that includes flexion
and extension abduction and adduction and if you can do those four what can you also do
our good friend circumduction so that's that complex movement of these four
and then since it is a ball and socket joint it is also capable of medial and lateral rotation
let's talk a little bit about the ligaments here we will save our discussion of the specific
muscles for another video but you are going to have a complex of ligaments that will surround
the articular capsule and provide a considerable amount of strength and by far the largest and
probably most importance definitely most important clinically will be your iliofemoral ligament and
it tells you exactly where it attaches it attaches from the ilium to the femur it's
going to be anterior and superior and very large it will cover up the majority of the pubic femoral
ligament which is also anterior and sometimes in some literature you will see this referred to as
the strongest ligament in the body i don't know how true that claim is but you certainly will see
it and it's certainly a very robust ligament so it's on up there if not the strongest and it will
play a role in terms i play a very important role in terms of preventing hyper extension
so not allowing for the hip joint to extend well past anatomical position that's why you can't
hyper hyperextend as much in the hip joint as say you can in the shoulder joint
you will have two other ligaments that are not as large you'll have the pubofemoral ligament which
you can see a bit of here it will actually extend a little bit deeper but is completely
covered by iliofemoral the more superior you get this will play an important role in terms of
preventing over abduction or ab duction and then the weakest of the three will be the ischiofemoral
on the posterior side of the joint so this will will be seen here and you can see that
it is covered a little bit even by the iliofemoral even on the posterior side
but it's really this iliofemoral that i want you to spend the majority of your time focusing on
okay moving to the knee joint you will have this is similar to what we had in the elbow joint
region where you have three joints that are going to be within one joint capsule one of the bigger
differences is that they're gonna kind of work a bit more in unison than we had in that area you
will have two femorotibial articulations so you'll have a medial and lateral so basically where
the medial condyle of the femur articulates with the medial condyle of the tibia and the
same thing on the lateral side and you'll also have a femoropatellar articulation so where the
patellar surface of the femur is articulating with that largest sesamoid bone of the body the patella
okay now two things i want to note before i move on one thing that you do not see here
you see the femur you see the tibia you even see the patella but you do not see that other
leg bone associated with the knee joint so the fibula
does not play a direct role in terms of the knee joint now some of the collateral ligaments will
articular are will attach to the fibula but it is not directly articulating with any
of these bones in this region to play a direct role in terms of the knee joint
and also importantly this joint is relatively weak mechanically and that has a lot to do with the
fact that there's not a good fit between the bones you have a very shallow tibial condyle with a
fairly robust fibular condyle so just mechanically weaker than some of the other joints of the body
now the knee joint is a modified hinge joint so there will be flexion and extension that's going
to be the primary movements allowed at the knee joint and so you can see with flexion instead of
moving anteriorly like most flexions when we're talking about at the knee joint the flexion will
have will bring that lower part of the limb to the more posterior side extension is moving back to
anatomical position also importantly some gliding and rotation can occur and this happens so the
when the knee is fully extended with the foot on the ground so the foot is planted on the ground
the knee will kind of passively lock in place with a little bit of medial rotation all right so that
locking will allow for muscles to relax briefly without making the knee joint too unstable
so that kind of will allow for a little bit of resting and not having to forcefully contract
those muscles to allow for a full extension of the knee and to unlock the knee just a small amount of
lateral rotation is needed so i mean when i say there's rotation i mean very very slight rotation
just to allow for a little bit of a better fit in terms of the articular surfaces there
okay let's talk ligaments and there are a lot of ligaments when we're talking about the knee joint
and probably the largest and some would argue the most important will be the patellar ligament it's
actually the distal part of the quadriceps femoris tendon so you can see at this point it's going to
be the tendon and then from the part from the patella to the tibial tuberosity which would be
just deep to this since it's connecting bone to bone it is considered a ligament so this would
be the patellar ligament this would still be the tendon i mentioned again it will be it will
attach on the patella to the tibial tuberosity and or the anterior superior part of the tibia
and this is the with a capital t h e the anterior ligament of the knee and you actually don't have
a complete articular capsule so the anterior portion of the articular capsule of the knee
is incomplete and really this patellar ligament with some of the retinocula from the tendon
of the quadriceps so this kind of complex right here really plays a role in terms of
serving that function of the anterior portion of the articular capsule of the knee
you have two collateral ligaments and they will tell you exactly where they are going
to attach you will have the fibular or sometimes referred to as the lateral
collateral ligament so from the fibula up to the um femur and this particular collateral ligament
is going to be more it's going to be rope-like it's going to be a very strong ligament
you'll actually have a tendon that will run just deep to this ligament the popliteus muscle
and will pass deep to it so it is completely separated from the capsule
the tibial collateral ligament is going to be considerably weaker than the fcl and sometimes
you hear the tibial collateral ligament referred to as the medial collateral ligament
and as i mentioned this is going to be the weaker of the two collateral ligaments
and also very importantly it is going to be attached to the medial meniscus we'll talk
about that in just a moment but it it's going to have an attachment to the medial meniscus
so let's talk a little bit about those miniski recall meniscus are going to be fibrocartilaginous
kind of incomplete discs that are located on articular surfaces and in this case these are
going to be located on the articular surfaces of the tibia and recall those tibial condyles are
very shallow so these miniski are going to kind of allow for a little bit of a better fit it also is
going to play an important role in terms of shock absorption and the medial meniscus is going to
have it's going to be firmly adhered to the deep surface of that tibial collateral ligament
on that side so that implication of such a close connection between those two structures means that
if one of those structures gets injured it's very likely that the other one will as well
so that attachment between these two structures is key the lateral meniscus is nearly circular so
you almost have a complete circle but not quite and it tends to be smaller it is going usually
it's going to be less frequently damaged than the medial meniscus and last but not least are the two
cruciate ligaments and you can see they form this almost crisscross shape within the joint
region so these are going to be intracapsular or within the capsule region the anterior cruciate
ligament is as its name would suggest the more anterior of the two cruciate ligaments
and it's also going to be the weaker of the two cruciate ligaments so if a cruciate ligament is
damaged it is almost always the acl and it also in certain resources you will see it may have
an attachment to the medial meniscus as well so oftentimes you'll have that complex of those three
structures injured and we'll talk about that in a bit more detail in a moment
but really this acl plays an important role in terms of preventing anterior displacement of
the tibia on the femur so does that tibia move too far forward that could indicate that there is some
type of damage to the acl and vice versa if you see too far of posterior displacement of the femur
on the tibia that could be indicative of an acl injury the posterior cruciate ligament
is kind of doing the opposite of the acl but a little bit better in terms of the fact that it
is less frequently damaged it is a bit stronger of a ligament it is very important in terms of
stabilizing the femur when walking downhill or say walking down stairs it's going to play an
important role there so whereas the acl would prevent anterior displacement on the tibia
of the tibia on the femur the pcl will prevent posterior displacement of the tibia on the femur
and so again let's kind of return to some of the clinical correlations that are associated with the
knee joint and recall that we talked about this really close connection between the tcl or the
tibial collateral ligament and the medial meniscus saying that they are very often injured together
and also oftentimes added to that mix is the acl and so if you have an acl tcl
and a medial meniscus injury this is referred to as the unhappy triad and it is ever so unhappy
because you can have a complete rupture or a tear of these structures it typically happens
with a blow to the lateral side of the knee which is kind of counter-intuitive because these are
more medial structures particularly the tibial collateral ligament but that force kind of moves
through that region causing this also excessive twisting can play a role or excessive rotation
can play a role in terms of damaging these three structures particularly with twisting
on that acl is often considered now can these be these structures be damaged individually
they absolutely can you can have just an acl injury or you can have just a tcl injury but
due to their close proximity and their relative weakness
it is not uncommon to have two or three of these structures injured at the same time
all right excellent so that is the hip and the knee joint some of its highlights so let's go over
this question together so the anterior portion of the articular capsule is incomplete which
ligament functions as the majority protection of the ant anterior knee is it the acl the fibular or
lateral collateral ligament the patellar ligament the posterior cruciate ligament or the tibial
slash medial collateral ligament so let's think about the stem here so this first sentence is just
a statement this is true the anterior portion of the articular capsule is incomplete that's just a
statement but it kind of is telling you that we need to be focusing on this anterior portion so
which ligament is going to kind of play the role of that articular capsule on the anterior knee
so we can go through these ligaments and see does do these make sense in terms of providing
protection to the anterior knee the anterior cruciate ligament has anterior right there in
the name so we might want to keep that one around to consider more fibular or lateral collateral
ligament is a collateral ligament so those collateral ligaments are always going to be on
the sides so not so much in terms of an anterior protection so we're not going to go with this one
patellar ligament where's that located well remember the patella is very anterior the patellar
ligament is between the patella and the tibial tuberosity so this is in the anterior portion
posterior cruciate ligament and not so much
it's intra-articular it's posterior so we're not going with that one and then
here's another collateral ligament so this is on the opposite side but still not so much anterior
so another part of the stem right here is saying the majority protection so anterior cruciate
ligament is going to be inside the capsule so it was never really going to play that big of a role
in terms of kind of taking over the end where the anterior portion of the capsule would be
and also it's not a particularly protective ligament either so we're not gonna go with that
one i think the patellar ligament if we return back to that image is really going to play an
important role in addition to the tendon which is really this is just an extension of that and the
retinaculum so basically this tendinous complex with the ligament being an important part of it
is going to play a role in terms of providing that anterior protection to the knee it is the anterior
protection all right excellent i love love love the hip and the knee joint um they are all so
complex and so different in terms of both movements and protection so they are they're
interesting to talk about but as you review these and as you try to get a handle on some
of these ligaments please make sure to reach out with any questions that you may have and i thank
you for your time and attention and we will move on to the ankle joint in the next video thank you