when we look deeper of the hand the hand has um multiple joints um so this is the couple bone right here so this is cavitate so this is the third um finger or middle finger so we have um the Met coule bone form the CMC joint with the uh cavitate and then we have the proximal finings form the mCP joint with the metac cou bone okay and then pip and dip okay so these are uh the bones and the joint for the CMC joint which is the corpal Met couple joints you see here um the second and the third CMC is most like you know almost not moving uh almost I said almost okay and U the thumb seem C uh and then the four the ring finger and then the little finger CMC kind of more U mo mobile compared to the second and the third so you can see that when um you make a PO uh grip U that I just mentioned and when you move your thumb like you know U moving your thumb to touch your little finger that's the CMC moving so um so that's the CMC joint and for this slide I have to change um the we that I present I typically have the joint movement and then know the next sline will be the muscle uh that uh contribute to the to the uh motion but because hand is so complicated I cannot really uh introduce that way because that would just make the slide kind of long enough so I'm going to change changing the way of uh presenting here okay so looking deeper uh for the thumb CMC motion right here so s a thumb CMC is a saddle joint you can see that you know this this sadle shape of the met coverable and then the trapezium it really allow the thumb to have um um different movements so here are the confusion part so uh I want to be careful and clear to you that uh these are the terminology that um shows on the textbook and it can be it can be really confusing so um uh I'll try my best okay so if we have our form supern uh and then all five digit kind of close together so see this is this uh the starting point if we move our thumb up you know pointing to the ceiling that the thumb is making a Palmer abduction or you can see in other textbook uh they take out the Palmer and just solely the abduction okay so let's go back to the original position if you move your thumb outward or away that's called radio abduction um in some textbook they call it extension so this is kind of confusing because extension can move backward like you know this is flection this is um um um extension so um that's why it's kind of confusing so I want to I want to show you this so you don't you don't get um too much trouble and understanding this these terminology so let's go back so when you move uh from Radio abduction or extension and move back that's called adduction yeah confusing right because I just told you that in other book it's called extension yeah that's why it's really confusing so uh so the move when the thumb move from uh an outside uh which is called uh radio abduction going to move back that's called abduction when you try to bend the finger even more you know um to uh kind of kind of try to try to touch the um the on side right here that's called CMC flexion that's when the CMC is make doing a flexion okay um so that's that can be really confusing right and what's not confusion is uh opposition because opposition is really uh using the pad of the thumb try to touch the P of the uh little finger or ring finger or even middle and index finger that's called opposition okay so let me repeat so thumb CC movement U has uh different terminology uh for that so when the starting position position of the thumb if you if we U superate our forearm and the Palm is facing up to the pointing to the ceiling like this and then when we move the thumb up you know pointing the thumb on to the ceiling that's called Palmer abduction in other book it also called abduction okay and then you and then we move the thumb back that's also called uh adduction about right away so okay and then when we move the thumb away to the side that's called radio abduction or extension and we move the thumb back that's called adduction right yes so that's why I personally prefer to call Palmer abduction and radio abduction because when we return to the original position it's called abduction that's easier to understand but um don't be surprised that U people will call it abduction and extension and you're like okay uh I need to think about that so that's why I want I slow down on this slide and then really uh explain that to you so this is the CMC motion okay and then the next joint is M mCP joint or MP joint so uh mCP joint um is uh is a convex um with the concave um joint surface like this it's it's really important that you know uh the stability of uh for the mCP joint is really counting on the uh collateral joint I'm sorry collateral ligament is if it's on the radial SI called radio collateral ligament and then the on SI called owner collateral ligaments okay so um this liament um is tight when the the mCP is a fraction in 90° um so imagine this if one person heard on the mCP and it got swollen and people you know try not to bend because when you bend it's just really painful so people or edema edema will just you know you know make the mCP in more uh extension position so what happened when the mCP is positioned in extension or in a more extended way uh what happened to the collateral ligament they will become loose right because they're not tall they're not tight and then as time goes it it'll become shortening right and then when when it got shorten when you got shortening then this person will have hard time to bend the knuckle then it can be really problematic because we we really do need that 90 Dees of the mCP joint so that we can have a fire motor um or going to manipulate or the object using our fingers so it's really important that you know that the co ligaments at you know around um um the mCP joint are tight at the you know flection in 90° and in this position um the joint is in the close pack position um that that would would not allow too many movement for that okay so it has multiple reason that you know after injury when we position the hand we U the textbook always tell you to position the r dmcp in the flexion position and the hand surgeon will really ask you to position the mCP in 90° and you must be uh you must know why and the C ligament is Tau and that's why uh the hand surgeon would prefer uh to put the hand in 90 degrees okay so and the mcps uh we do uh abduction adduction like we're saying no with our index finger uh or fraction extension and some people may have some uh the hyper extension uh I my index finger can do a little bit of index finger but not my other fingers but some people can do like all uh four fingers uh doing the hyper extension okay so in general the mCP will do flection extension abduction and adduction okay the IP joint so the uh the finger would have two IP joints one proximal inter plal joint and then this to uh inter lro um joint and the thumb um has only one IP joint okay the IP joint only allows um people do inflection and extension and again it really depends on uh the CL recomends for U the stability of the joint