Hello all this is Dr Alsup and in this learning objective video we will be discussing the joints
of the hand. So all of those long name joints that we introduced in the first MSK session
we will spend a bit of time discussing what types of actions can occur at these joints
and again just really trying to identify them.
We will start with the most proximal of the joints of the hand and these are the carpometacarpal
joints often abbreviated so we don't have to say carpometacarpal so many times to CMC.
These CMC joints are formed by the articulation between a carpal bone in the distal row and a
metacarpal so they are going to be located in this general region and there will be five CMC
joints in all one associated with each digit. Most of the carpometacarpal joints are plane joints so
2-5 will be plane joints, so there will only be gliding movements allowed at the CMC
joints. The one exception is the thumb the first digit or the thumb where this particular
CMC joint is a saddle joint and capable of considerably more types of movements with a
greater range of motion and you can kind of just do this on your own try to move your CMC joints
of 2-5 not so easy but try to move your first CMC joint and you have quite a bit
more going on there. So the carpometacarpal joint of the first digit is capable of flexion
and extension which uniquely in the thumb is going to occur in the coronal plane.
So flexion can be moving in the coronal plane towards the palm as you can see here and
extension is going to be away from the palm such as like jutting the thumb out laterally
like in what is sometimes called a hitchhiker's thumb.
Now most abduction and adduction is going to occur in the coronal plane, but in the thumb it's
going to occur in the sagittal plane. And I often describe abduction of the thumb as say you're
looking straight at the palm of your hand and then you try to touch your nose with your thumb
that's going to be abduction. It's also what you do when you are using a sock puppet.
Adduction would be moving it back towards the palm. Anytime you can flex, abduct,
extend, or adduct you can also circumduct and that would be making a circular motion with the thumb.
These some of these movements that we've described here are vital in the complex
movement of opposition that can occur at the thumb. And by complex I mean it
involves different kinds of actions for more than one joint but the actions of the carpometacarpal
joint of the first digit are very important in terms of us being able to have opposable thumbs.
Okay let's move distally to the metacarpophalangeal joints another
name that has mercifully been abbreviated but there is not as
much standardization here sometimes you see the MP joints sometimes you see MCP joints.
This is going to be the articulation between the metacarpals, so these are your metacarpals
here in orange, and the proximal phalanges, so i'm drawing a line through the MP joints.
And if you're looking at your own hand the MP joints are what we commonly call your knuckles.
Metacarpophalangeal joints are condyloid joints which means
they are capable of flexion, extension and also abduction and adduction
and then of course as you know if you can do these actions here you can also circumduct.
Abduction and adduction in the hand is not the typical definition of moving towards or away
from the body. Instead abduction in the hand is going to be moving away from the third digit,
whereas adduction is moving towards the third digit, so we have a different plane
through which we're moving it's all focused on this third digit.
The first digit MP joint is typically described as a condyloid joint like all the rest
but it's mainly just capable of flexion and extension.
Now onto the many many interphalangeal joints the good thing is that these are all hinged
joints so there's no differences here, so that's easier to remember, so they do what any typical
hinge joint does which is flex and extend. There are two main types of interphalangeal joints
there are the proximal interphalangeal or PIO joints, you can see where those are located here,
and there are the distal interphalangeal joints or the DIP joints, which are between
the intermediate or middle phalanx and the distal phalanx.
By the way I love saying PIP or DIP. Recall that there is no intermediate phalange in the thumb
so there's just the one interphalangeal or IP joint which you can see right here. Okay excellent
we have reached the summary slide which is your one stop shot for the foundations of the joints
of the hand. Please review and reach out if you have any questions have a great rest of your day