- [voiceover] arthritisis a term that we hear all the time, right, butto break down this word, arthritis, -itis means inflammation. everywhere in medicine it's gonna refer to inflammation, and whatever before it is telling us where the inflammation is. in this case, arthr-is referring to joints. now we have joints inour body that don't move, kind of like pieces of ourskull that come together.
those are not meant to move, and it's just holding our head together, but the joints that we're thinking of and the joints that we're gonna talk about are the joints that do move. your knees, your elbows,so on and so forth. in those joints, therough structure, pattern, is always gonna have the end of one bone and then another bonewith a space in between
that is enclosed by a joint capsule, and it's lined withsynovium, or synovial lining, which produces a fluid that we call synovial fluid to lubricate, and on the surface of thesebones we have cartilage. so that's gonna be the rough structure, and i'll draw this inmuch better detail later. any kind of joint inflammationqualifies as arthritis, and there's actually alot of different kinds.
so if we ask ourselves,"what is arthritis," i wanna go through someof the big categories of things that qualify as arthritis, and the kinds of people thatare likely to get each kind. but the first category is probably the most common category, and that's gonna be arthritisfrom overuse of the joint. this is probably what yourgrandma is talking about when she's saying, "my knee hurts.
"i have arthritis." and the thing is, you and iwill probably get this kind of arthritis too if we'relucky to live long enough. so the groups of peoplethat are most likely to get this kind arethose who are elderly, because they've lived longer and have used their joints longer, and also people who areobese and overweight, because the extra weight they're carrying
just weighs down their joints. so obesity is correlatedwith more overuse, or osteoarthritis. speaking of which, osteoarthritisis the poster child for overuse arthritis,osteo- meaning bone. arthritis. i'm not gonna write this out every time, so from now on i'm probablygonna refer to it as oa. lots and lots of people get this,
usually in the weightbearingparts of their body or whatever is overused the most. for example, a typist might get this in her fingers or wrists. a dancer might get it in her knees. this is due to rubbingaway of the cartilage and general wear and tear on the joint. we'll go into the specificpathophysiology later. the second big category,
and it really qualifies as a big category, because it includes a lotof different diseases, this one's gonna be autoimmune. so auto- means self,and immune is referring to our immune system, which is usually the system that helps us fight off invasion from the environment. so essentially the bodyis attacking itself, and some of the famousdiseases in this category
you might have heard of. they include lupus, crohn's disease, and they're often systemic, means they reach a lot ofdifferent parts of the body. the population, if we had to bet on the biggest populationto have these diseases would be females, usuallymiddle-aged females, but for now we're just gonna say females. of course guys get them too,
but if we're going with our odds, it's more common in female patients. so autoimmune arthritis. at the top of this list hasto be rheumatoid arthritis. rheumatoid. aside from oa, this isthe other huge category of people with arthritis. rheumatoid arthritis. and even though it'svery different from oa,
they're often contrastedagainst each other because these are the most common kinds, so when we're diagnosing,we always wanna see if they're leaning towards oa or ra. so compared to oa, the patients on average might be younger, butof course elderly people get ra as well, but as you will see later, the symptoms look very different. there's a whole branch ofmedicine called rheumatology
that deal with rheumatoid problems, so that kinda suggestshow widespread it is. the thing is, rheumatoidarthritis has a unique thing we can isolate from testingthe patients' blood. it's called rheumatoid factor. i'm gonna write rf. rheumatoid factor issomething you can test for, and it pushes you towards a diagnosis of rheumatoid arthritis.
now i'm mentioning this becausethe rest of the diseases that went on the list inthe autoimmune section are collectively referred toas a seronegative arthritis. this is referring to thefact that in their serum, they don't have rheumatoid factor. so this whole categoryis there to separate rheumatoid arthritis from the other autoimmune arthritises. arthritises, i don'tknow if that's a word,
but that's what we're gonna call it. so seronegative is thefirst part of the word. the other half of thecategory refers to the fact that these diseasesoften involve the spine, not just the joints in ourlimbs that we think of. so spondylo- refers to the spine, so spondyloarthritis. the name here tells you a lot. it tells you that it'snot gonna be rf positive,
and it's gonna involve the spine. so we have ankylosing spondyloarthritis. ankylosing means afusion, fusing together, which is a common symptom in a lot of different types of arthritis, but here it's part of the name. ankylosing spondyloarthritis. such long words. spondyloarthritis.
i'll probably refer to this as as. everything's about acronyms in medicine. and then we have reiter's syndrome, named after the personwho found the disease, reiter's syndrome. then we're gonna have psoriatic arthritis, psoriatic, which is part of psoriasis, one of the autoimmune systemic diseases. but it also causesinflammation of the joints,
so psoriatic arthritisis its own category. with the seronegative spondyloarthritis, one buzzword i want you to remember is called hla-b27, i'm sorry, not seven. for those of you taking tests,this counts as a buzzword. every time you see it,think of the seronegative spondyloarthritis diseases. this is an antigen, surfaceantigen on an immune cell.
so all that means is if wehave a white blood cell, hla-b27 is an antigenthat can attach to it, and it's something that thesediseases have in common. we don't have to go toofar into immunology here, but just remember,cement these four letters and two numbers into your head, hla-b27, and think of autoimmuneseronegative spondyloarthritis. all right, moving on. the next category is gonnabe nice and straightforward.
it's gonna be infectious. even though usually the joints should be nice and closed off tothe outside environment, sometimes an infection gets through, and this can give us arthritis, so the most dangerous kindis gonna be septic arthritis. so sepsis refers to an infection that's leaked into the blood. so septic arthritis, thisperson's gonna have fevers
and systemic symptoms, but the original problem's gonna be able to be traced to a joint. and the people that aremost likely to get this are young males. think of college-agedkids, maybe slightly older. some of the bacteria responsible include gonorrhea, chlamydia,which are the big ones. also bacteria that live on the skin.
so think of infection if thearthritis came on suddenly, it's pretty severe, and we'reseeing systemic symptoms. speaking of which, iwonder if reiter's syndrome also fits in the infectious,because it's associated sometimes with certain viral infections, and it can develop as anaftermath of that infection. but i guess it belongs better up here, because it's not an active infection. but as we get to reiter's syndrome later,
we'll talk about that in more detail. so far we're talked aboutoveruse of the joint, of things inside the body, the immune system attacking the joint, outside things attacking the joint, and the last category we're gonna have is gonna be things depositing in the joint that really don't belong there. don't really know what to call this.
let's call it depository,if that makes sense. depository. so there's not reallyanything attacking it per se, but the joint shouldbe a clean, pure place, and particles that deposit there can cause a lot of inflammation and pain, and you probably already knowwhere i'm going with this. it's gonna be gout and pseudogout. we think of these usually areisolated to certain joints
in the body, and theyalmost always occur there, but of course they canoccur in other places too, and it counts as arthritis because it's an inflammation of a joint, and they both come fromdepositing certain proteins in the joint space. so these four big categories round out the big things that werefer to as arthritis. all these diseases are so different,
so the next time you hear arthritis, remember that's not thestereotypical knee pain that we're thinking of. so really pay attention to the symptoms that distinguish these different kinds of arthritis from each other.