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Joints of the Shoulder Girdle and Scapular Joint Actions: Video #6 of Introduction to Functional Anatomy
In Video #6 of Introduction to Functional Anatomy, the anatomy and biomechanics of the shoulder girdle and scapular joints are introduced. The video covers the four main joints within the shoulder girdle - namely, the sternoclavicular, acromioclavicular, glenohumeral, and scapulothoracic joints - as well as their roles in allowing optimal movements of the shoulder. In addition, the video also examines how these
Transcript
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So let's talk about joints of the
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shoulder girdle. We just learned all
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these joint actions and now I'm going to throw a little wrench in our joint
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actions chart, but joint actions of the shoulder girdle are acromioclavicular joint
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and our sternoclavicular joint. Now those sound
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like really huge, technical words, well remember when I was talking about
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anatomy being another language, those aren't huge technical words, they're
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actually referring to two specific bones or two specific points with on a bone.
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Your acromioclavicular joint everybody feel this right here, feel that shelf
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where you don't have any de ltoid, it's just above your deltoids, it
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doesn't matter how big your deltoids are you still don't have deltoids here.
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Right here you feel the shelf, well that's part of your scapula called your
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acromion process. What's this bone right here called? This is your
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clavicle, your collarbone it's your clavicle, so where your acromion
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process and your clavicle meet is called your acromioclavicular joint. That's it,
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it's not so bad right. It's like when you try to smash words together, you guys
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ever do that, like you see a cute couple and you like try to smash the girls name
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and the guys name together, you guys ever done that before? Right don't they do
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that with like stars, huh Kimye, awful, terrible. Anyway, but you get what
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I'm saying, that's all they've done here, taking acromion and
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clavicular and said, "You know what'd be really cute? If we call it acromioclavicular."
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That's the name of the joint, for short it's AC joint. Sternoclavicular, what do
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you think sterno is related to? Sternum and the clavicle feel right here,
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do a little of this, you can kind of feel there's a joint right here.
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The funny thing is is your entire shoulder girdle including your
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arm, the only bony attachment to your body is this joint right here. Craziness.
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That's crazy. Alright so that's your sternoclavicular
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joint. Now although those are the two joints of the shoulder girdle, we don't
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usually refer to motion of these joints. In further classes you will, those of you
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guys going back for your ATC, your DPT, master's in kinesiology, you'll start
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looking at these joints specifically, but for the most part those two joints help
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to dictate motion of the scapula, and we refer to motion of the scapula in
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analysis. Most of the muscles that would even impact these joints are actually
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attached to the scapula, does that make sense? So I don't want you guys to think
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that the scapula is a true joint, sometimes it's called the scapulothoracic joint.
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It's not actually a true joint, it's just more convenient to label
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it that way. Now unfortunately you guys just learned all of these joint actions
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right, flexion, extension, abduction, adduction, horizontal abduction, adduction
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external internal rotation, lateral flexion, you learned all that. The
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scapula doesn't use those, so we have to learn a separate set of joint actions.
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You ready? They're actually not that bad. Most of them occur in the frontal
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plane. Does anybody want to take a wild guess why most of them would occur in
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the frontal plane? Think about how I taught you guys the frontal plane.
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The muscle, the way the muscles run, that's part of it. I told you to think about the
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frontal plane as if you had what? A plane of glass in front of you. What's in
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front of the scapula? The ribs. Is there going to be a whole lot of sagittal
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plane motion of the scapula with ribs in front of it? Now that kind of makes sense.
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So our frontal plane joint actions, our scapular joint actions rather
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start with,
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that's my scapula everybody cool with that, all right start with this. If I go
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up it's called elevation, because elevators take you up, I know they can take
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you down too but stay with me. So elevation is up, that makes sense right
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that's not too bad. What do you think the opposite of elevation is? Depression.
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Don't most people who are depressed kind of have their shoulders down anyway.
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Okay so we got elevation, we have depression.
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The next joint actions you kind of have to think of the scapula as a pinwheel.
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You remember pinwheels? They were these little, there was like a stick,
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stick, right then they had these like leafy things, how's my art coming?
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Is it getting better? Better than the horizon, that kind of looks like a
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pinwheel and you'd like blow on it and it would spin, you know what I'm
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talking about? Or am I just totally dating myself at this point. Pinwheel?
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You have to kind of think of it as a pinwheel, it's a type of rotation
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although it's a rotation in the frontal plane this way, known as upward and
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downward rotation. Now to decide which way is up and which way is down we need a
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point of reference, you with me? That point of reference for the scapula is
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your shoulder socket, this part where my humerus hangs down my arm, this is known
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as your glenoid fossa. When your scapula spins so that we end up with
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glenoid fossa pointing upward, which rotation do you think that is? That's
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upward rotation, moving back down is going to be downward rotation. What do
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you think we see these joint actions, anybody want to take a guess? Frontal
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plane motions sure, give me an exercise? Shoulder press would be what? Upward
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rotation, when would I see downward rotation? Pull up, so if
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I'm doing a pull-up, my scapulae are starting to do this, which is that downward
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rotation. Has everybody got that visualized? Alright let's talk about the
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last ones.
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If I drew you from the top, this is your torso this is your head, sorry if any of
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you are offended by this picture I don't mean anything by it, not that big, it's my
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torso. So we got torso head and then we got scapula, it's a great picture isn't
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it. If I do this, all right if I do this thing, so in essence I go from here to
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here, can you see how that would be transverse plane movement? Parallel
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to your table since this is a top-down view. Now the question is what do we call
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that? This is protraction. How many of you have seen this guy in
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the gym, you can now refer to them as Captain Protraction. No? None of you
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are that nerdy? Any of you know what ILS stands for? This is a good one
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too, you don't know ILS? "Imaginary Lat Syndrome." You can throw
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that around amongst yourselves. So protraction, what action, what
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exercise might we see a little protraction in? Benchpress sure, we really
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need protraction to bench pres. In fact, anytime we do pushing motions, we need
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some protraction. What's the opposite of protraction? Retraction, so that's
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when my scapulae actually come closer together and almost touch in the middle.
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We got the green as protraction, when we got red we got retraction.
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Those six joint actions are your big joint actions for the scapula,
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those are the ones you will see most often, you guys cool with that? Now there
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is two other joint actions for the scapula that you don't run into as often
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in your textbooks. Those of you who continue with my courses you're going to
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have to be aware of, which is there is one set of sagittal plane motions for
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the scapula. It's called anterior and posterior tipping. So we won't refer to
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this too much for the rest of the day, you can put a little star by this,
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as bonus material, but if I drew a skeleton from the side,
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all this are my vertebrae, how you like my picture? Good. Scapula sits just
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like this. Now anterior and posterior tipping is sagittal plane motion, which
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means it's in which direction? Forward and back right? So what happens with the
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scapula is it can kind of crawl over the top of the rib cage, and it can tip
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anteriorly. Alright so when we refer to this tipping it's in reference to the
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top of the scapula, and then what would be the opposite of anterior tipping?
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Posterior tipping, exactly. So that would be posterior tipping. When we get into a
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little bit more complex postural dysfunction and correcting postural
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dysfunction and improving mechanics of the the upper body, this becomes
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important. Everybody's got those? Anybody want to take a guess when anterior and
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posterior tipping happens, like some exercises? Shrugs, yeah you don't really
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force it in a shrug. It's probably going to be more like an arm motion that
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anterior and posterior tipping gets included in, anybody want to guess?
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Swimming possibly, when during the swim? So if I do this, what's going to
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happen to my scapulae? They're going to posteriorly, do it, do it, you can feel your
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scapulae push into your rib cage, it flipped this way, so that's
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posterior tipping. Anterior tipping is, yeah if you did one of these
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things, everybody do this, because it looks hot, like Kimye,
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