hello anatomy colleagues this is dr alsup and we are going to finish
our discussion of the upper limb joints with the more distal major joints in this region
again recall that we discuss the joints of the hand so those between the phalanges and
the metacarpals when we were talking about the osteology so the focus of this video will be
on the elbow joint and kind of a surprisingly complex region the proximal radial ulnar joint
in addition to kind of talking through just radio ulnar joints in general because there's more than
just one and lastly we will finish with the wrist joint or the radiocarpal joint all right so what i
think is really neat about the elbow joint and we'll have something similar in the knee joint
region as well is that really there are going to be three separate joints in one joint capsule so
one articular capsule is going to surround three different joints so you will have the humeral ulna
so right here this is humerus this would be the ulna this is what we typically think of when we
think of the elbow joint you'll also have the humeroradial so where the head of the radius
is going to articulate with the capitulum of the humerus and then also you're going to have
the first or the most proximal of the radioulnar joints so that proximal radioulnar joint
and we will kind of look through that region in a bit more detail later but it's important
to note that all three of these joints or all these articulations have a common joint capsule
all right so when we think of the elbow joint we're really thinking of that humeral ulnar joint
the humeroradial joint will play a small role in in terms of some of these actions
it's really that humeroulnar that's playing the big role in terms of that hinge joint and
this is kind of the example of a hinge joint you can very clearly flex so if you say this is
the arm you can flex the uh the elbow joint so you can see kind of reducing the angle
and then extension would be increasing the angle kind of going back towards anatomical position
so try flexing and extending your own elbow you always think of like i'm flexing and i'm
kind of showing my muscles you could show that biceps brachii
when we're flexing the elbow joint because that's one of the muscles that's contracting
again here if you click on this link there are videos of these different actions as well
now we're getting into the first of these collateral ligaments and we'll have these
particularly in association with hinge joints but what these will be are going to be ligaments that
will be on either side the medial lateral side of a joint so we'll have some collateral ligaments
associated with the wrist region with the knee region and we have some of the elbow region and
the great thing about these are they tell you exactly where they are attaching so that ulnar
collateral ligament is going to be on the ulnar or the medial side whereas the radial
collateral ligament will be on the lateral side it's really this ulnar collateral ligament that's
one of the more stable of the ligaments this radial collateral ligament is also going to have
some of its fibers intertwined with this annular ligament that's surrounding the head of the radius
both of these are considered capsular which means that they appear as thickening of the capsule or
the articular capsule now the articular capsule's been removed in the anterior and posterior
portions but if you add this back in it would just like look like a thicker portion on either side
okay let's talk a little bit about the radio ulnar joints in general and there will be three
radioulnar joints we're going to spend the most majority of our time talking about the
proximal radioulnar joint which will be between the head of the radius and right
here in terms of that radial notch of the ulna so right here will be the proximal radioulnar
this is going to be a pivot joint and so it will allow that radial head to kind of rotate
along or around the radial notch of the ulnas we'll talk a little bit more about that action in
a moment but before we move away from this image um and here's another view of that proximal radio
ulnar but before we move away from the image i want to talk about the other radioulnar joints
you're going to have a very kind of similar one in the distal
distal most portion the distal radioulnar joint which will be between
excuse me the head of the ulna and the little notch for the head the ulnar
notch of the radius so that will be the distal radioulnar this will also be a pivot joint
and then in the middle connecting the two bodies or the shafts of the radius and the ulna you will
have another joint which is the interosseous membrane and we recall in our discussion of
joint the interosseous membrane is going to be a fibrous joint so we're not a synovial joint
in the area between the the bodies of the radius and the ulna so that syndesmosis type of joint um
it will allow some movement in particular kind of when you have the pivoting in these two regions
you do need a little bit of movement of the body because it's really when we're talking
about pivoting and the bone that will be moving uh in these particular actions it is all about
the radius it is the radius that will be doing the pivoting and the rotation and so that movement
that will occur with the proximal radial ulnar joint and i have here with the distal radial owner
it will be what's called pronation or supination and again it's that radius that is the one that
is going to be the moving bone and so in supination and this is key here the radius
and the ulna are going so this is radius this is the ulna these are going to be parallel to
one another this is anatomical position so palm is facing forward uh the two bodies or the two
shafts are parallel to one another and so we are anatomical position whereas in pronation
you're going to have that radius rotating over the ulna and this will be pronation
if you think of pronation it's almost the opposite of anatomical position so you have
those palms facing posteriorly or if your elbow is flexed the palms would be facing inferiorly
i don't know what happened here i apologize but the annular ligament is going to be an associated
ligament of the the proximal radioulnar joint and as i had mentioned previously it will completely
encircle the radial head so both anteriorly and posteriorly and it really kind of helps
to lock in that connection between the ulna you do have that radial collateral ligament that will
that will have its fibers kind of intertwine with the annular ligament
now there can be a dislocation of that radial head away from the capitulum and away from
the radial notch of the ulna and this is referred to as a subluxation or an incomplete dislocation
or you can have a complete dislocation and this is more commonly referred to as a pulled elbow
and what will happen is that radial head typically will move distal to the annular ligament now we're
looking at a radiograph where this has occurred and i want to note something here you can see
that we look like we have a completely separated epiphysis from the diaphysis with some growth
still occurring here so this is a growth plate right there so you have a good indication that
we're looking at a juvenile in this radiograph which is not uncommon when you're talking about
this type of injury in fact it is considerably more common for this to occur in juveniles and the
reasoning behind that is the annular ligament kind of gets to its larger size or it's more adult-like
sizes a little bit earlier or faster than the radial head does so if you have a quick jerking
of the forearm that can cause that radius or the radial head to move inferiorly and kind of pop out
it'll make that noise out of the annular ligament and so generally you can kind of just place this
back into its proper positioning without too much further damage but if it does involve some type of
movement or further distancing between the epiphysis and the diaphysis that can have some
issues as well so that's why i always tell people don't pick up your your children by the hands and
kind of swing them around because that you want to keep those radial heads nice and protected
okay last but not least the we're going to discuss the radiocarpal joint which is more
commonly referred to as the wrist joint and so this will be formed by the distal
end of the radius which is going to be the dominant forearm bone
you will have an articular disc that is going to be located right about this region here so
between the ulna and the proximal row of carpal so you do not have direct articulation of the ulna
as part of the radiocarpal joint that's why we say ulna plays a big role in terms of the elbow joint
little to no role in terms of the wrist joint but you do have an articular disc right there
and then um the proximal row of carpal bones will be what is forming the the
more distal portion of this joint so all three of those bones um will play a role the fourth
carpal of the proximal road the pisiform is kind of sitting right on top of the triquetrum
so it's not so much playing a role in terms of this joint that's one of those sesamoid bones
that is going to form in the flexor carpi ulnaris muscle
now the wrist joint is a as an example of a condyloid joint so you do have a considerable
amount of movement that can occur here so if we're looking at anatomical position right
here flexion would be kind of rotating up so think about if you're flexing your wrist those
fingers would be trying to touch the anterior forearm whereas extension you would be moving
back to anatomical position or kind of past that abduction and adduction abduction is going to be
again moving away from the midline sometimes this is referred to as radial deviation so abduction
can sometimes be referred to as radial deviation so deviating towards the radius whereas adduction
heading or moving back towards the midline is sometimes referred to as ulnar deviation
and again i sound like a broken record here but anytime that a joint can flex extend abduct and
add duct that joint can circumduct as well so try circumducting your wrist you absolutely
can make those uh circular movements there and that compound movement of these four
all right excellent we have made it to the end of the joints of the upper limb and one quick review
here because this action is a little unique i want you to make sure that you understand what
type of joint the proximal radioulnar joint is so what type of synovial joint is it is it
a ball and socket is it a condyloid is it a hinge a pivot or a saddle and if you need to pause the
video please feel free to do so but when you are ready to go let's work through the stem together
so we're trying to figure out uh which type of synovial joint is the proximal radial ulnar joint
okay so it's not a ball and socket joint uh the ball and socket joints that we've talked about
are really only the shoulder joint and the yet to be discussed hip joint um so not ball and socket
it's not condyloid either that is going to be that radioulnar joint and some of the other joints
but not not proximal radioulnar not hinge joint even though it is close to a hinge
joint so that humeral ulnar joint is a hinge joint and it's it's going to be kind of in
capsulated with that articular capsule but it does have separate movements that are not
hinge excuse me pivot i might want to come back to this one saddle joint not so much saddle is
pretty similar to the condyloid joint that's going to be between that first metacarpal and the uh
uh trapezium of that distal row of the carpal bones so pivot is going to be the correct answer
it will pip and by pivoting both the proximal and the distal radioulnar joints you can have
the movement of pronation and supination that we discussed earlier all right excellent good job
working your way through this question i hope you're feeling more comfortable in these areas
and if not you and you need some clarification on certain areas always feel free to reach out
to me with any questions thank you for your time and attention and have a great day