so before we really get into the discussion of the specific joints I want to talk about the
term range of motion and you'll hear me talk about range of motion quite a bit a lot
of times you'll see it abbreviated like that or sometimes you'll see ROM and degrees as well
because we're really range of motion is going to be measured in terms of degrees so there are a
lot of factors that are going to affect range of motion so you'll have the difference between the
most freely movable joint your shoulder joint which has a high range of motion compared to
sutures which has almost no range of motion so let's let's understand the components that will
allow those things to occur all right so range through which the bones of the joints can be
moved measured in degrees degrees in a circle so you can have zero degrees you can have ten
and you can get up to 360 now of course that's really not going to occur in terms of joints
within the body but you can understand how we're talking in terms of degrees in a circle now the
main thing that's going to affect range of motion is going to be the shape or the fit
of articulating bones do the bones fit together really well or are there is there less of a degree
in terms of fit so you the first thing that we're looking at here is the shoulder joint
or your glenohumeral joint and we'll talk about this in more detail in a subsequent lecture but
I want to kind of point these out here so you had the ball portion which is referred to as the head
of the humerus fitting into the socket portion or the glenoid cavity or glenoid fossa of the
scapula now that glenoid cavity is very shallow so the head of the humerus only about a third
of the head of the humerus can really fit there now that has a great great deal of implication
in terms of range of motion allowing for this freely movable joint here as opposed to if you
think about the bones of the skull fitting together in those sutures you have almost a
jigsaw puzzle fitting together and you have very little if no range of motion in terms of sutures
now other things that can affect the range of motion one of the main ones is ligaments
so certain ligaments of the body are going to be very strong and actually they can be components
of the actual articular capsule so is the case in terms of your elbow joint so you can see we have
two ligaments here anytime you have a hinge joint you'll often have collateral ligaments associated
with them and collateral ligaments really play a role in terms of not allowing medial or lateral
deviation of the joints so in the particular case of the elbow joint you have these very
strong capsular ligaments that are going to protect the sides of your elbow joint really
allowing for a flexion extension to occur with very little movement medial or lateral now you
have other types of ligaments you have ligaments associated with all of your synovial joints and
depending on the strength of them really will affect which way that particular joint can move
now one thing I don't have a visual here of is muscles muscles play just as important a role in
joints as well and range of motion so dependent on how well a joint is covered with muscles or
tendons that will affect the range of motion now one last thing I want to discuss is how hormones
can play a role particularly in terms of pregnancy now one joint that we've discussed before is your
pubic symphysis this is a type of symphyseal joint so we know we're talking a cartilaginous joint now
during pregnancy and particularly as you get later in terms of pregnancy so you'll have the release
of a very specific type of hormone referred to as relaxin relaxin we'll first of all and this
is something that's important to know will relax all the joints of the body okay so let's remember
that it's not only going to affect the joints associated with the pelvic girdle it will relax
particularly in terms of your synovial joints so all the joints in the body are a little bit more
loosey-goosey than they typically are but it's important in terms of not only relaxing the pubic
symphysis but your sacro-iliac joints as well now it's not completely going to fall apart of course
it's just going to allow for a more movement and allows for a widening of the inlet region
so the outlet and the inlet region and allow for child birth to occur so relaxin's an example human
growth hormone in terms of growing joints and the the particular components of joints are going to
play a role earlier on in terms of adolescence so while we think about fit a bone and ligaments and
joints hormones or part of your endocrine system are going to play a big role as well so let's
take what we understand in terms of this and let's move on to specific examples of joints of the body