hello and welcome to part two of the lecture on chapter 16 musculoskeletal system we had just finished off with joint injuries uh in general we were talking about damage to some of the structures in the joints and now we're going to look at one particular joint and that is uh the knee joint um I realize now that the little screen of my head maybe covering part of this diagram so sorry for that let's just talk about a little bit about the the structures that reinforce the knee uh there there's a four-headed muscle it's called the quadriceps here in the upper thigh you can hear the thigh and these uh four heads of muscle converge onto this one tendon the quadriceps tendon it attaches to the bone called the patella then there's a section of this dense connective tissue that continues on to the tibia that's the patellar ligament so quadriceps tendon and patellar ligament and then on the sides um the the knee is reinforced by these so-called collateral ligaments meaning they're on the outside they're on the sides of the knee joint medial and lateral collateral ligaments medial of course is on the tibia side and laterals on fibula side then let's take a look at the inside of the knee there are some other structures that help stabilize this there are two ligaments inside the knee that cross from the distal end of the femur to the proximal end of the tibia um the one in front is called the anterior cruciate ligament or ACL you may have heard of this one before and then there's one Crossing in the back posterior cruciate ligament in addition to those ligaments there's also these pads of cartilage these are called meniscus singular is meniscus and they provide extra cushioning this is a joint that takes a lot of pounding and as I've already mentioned the the collateral ligaments on either side and any of those structures can get damaged um this is a another diagram it's not from our textbook but it had a lot more detail the quadriceps tendon has been cut and then the whole patella has been reflected away from the knee so you can see the internal structures of the knee appreciate ligaments and the meniscus let's take a look at damage that can happen we can have sprains as in any joint um varying in in resulting in varying degrees of ligament tears of course of you know trade one grade two grade three the medial collateral ligament is one that is frequently affected and the way this gets broken is in um by a blow from the outside so in football for example the foot is planted and then somebody gets tackled from the side and that pushes uh towards the medial so from the lateral side to the medial side and that can lead to a rupturing of this ligament uh the ACL famously gives way 10 times more commonly than the PCL than the posterior cruciate ligament does the way to assess this is there's movement in the knee that shouldn't be there I mean the patient will report pain of course um but if the the knee can hinge open on the medial aspect it's not supposed to and if you can pull forward on the tibia um that indicates that the ACL has ruptured damage to the meniscus also happens this is it generally happens when the the knee is slightly flexed um and there's it's bearing weight that is the person is standing up and there's twisting motion and that crushes the the meniscus just think about if you've ever tried to kill a bug with your shoe you step and twist that's going to be the the most damaging Force you can do and that is what is happening inside somebody's knee the three cardinal signs of meniscus injury of course is the the tenderness The Joint line there's swelling and that the knee feels like it's locking in position to confirm the diagnosis this has to be done either with an MRI imaging or with actually going in and taking a look with arthroscopy uh that arthroscopy is also frequently required to pull out any broken pieces of cartilage all right that was fast and dirty on the knee now we're moving on to the back uh it's extremely common for people to report back pain and it can have all manner of causes um many of them just due to muscular over exertion there can be uh arthritis swelling of the joints but we'll cover that later here we're just going to talk about herniated disc disease uh let me remind you of the anatomy of the vertebral column we have vertebrae that are stacked on top of each other they uh articulate with the other vertebrae above and below them in two ways in the front they articulate um the whole body is just sitting on top of the body of the other vertebra there's uh not a lot of there's not a space here you have a a cartilaginous pad um it allows for some wiggling but these these bones are you know attached to this cartilaginous pad which is attached to the next vertebra those are the so-called intervertebral discs then in the back um there are processes that stick out see there's processes that stick out from oh my gosh how am I going to do this uh from each other and they articulate with each other in the back the bodies are on top of each other and then these you can get a little bit more wiggle room the synovial joints there we'll come back to those later also and there's a spinal cord running through this space here that spinal cord is part of the central nervous system and it gives rise to the spinal nerves that are part of the peripheral nervous system the spinal nerves have to come out in between the vertebrae these are called the intervertebral foramen um um all right so if the intervertebral disc gets squished in such a way that it pokes out a little bit if it pokes out to the front I mean it's still a herniation but it's not pressing on anything if it bulges out to the back or to the side there's a chance that it's going to press on the spinal nerves that's the big problem with the herniated discs so what we end up with is the disc you're in blue sticking out somewhere um and depending on where it's sticking out the sticking out part is shown in red um depending on where it's sticking out it's going to impact what nerves it's pressing on so again we can end up with the compression of the spinal cord itself part of the the central nervous system um but then it can be compressing the nerves that that are coming off what part of the nerve is being compressed um determines whether the the patient experiences pain there's Sensory neurons that are being affected or just motor neurons let me show you what I'm talking about it's the cross section of the spinal cord we didn't talk very we didn't barely talked about the spinal cord last week um but if we take a cross section through the spinal cord what you can see is that there's um organization in the spinal cord remember how we talked about there's sensory information coming in towards the central nervous system and then motor information coming out a parent and efferent Signal okay so there's that kind of um segregation of cells in the spinal cord um and so we have incoming signals they come in through the dorsal root through the back back door information is coming in and then outgoing information is through the front door the ventral roots ventral Roots so depending on which part of this is getting squished um that determines whether the person experiences pain or motor involvement weakness of the muscles that are being innervated by that nerve of course it can be both if both bits are being affected all right now we're Switching gears again we're going on to repetitive stress injuries the one example we're going to talk about is carpal tunnel syndrome but it can happen in other other joints um so involves muscles nerves tendons it's often occupation related you know something that a human being is going to do for hours and hours and hours and typically the only things we do for hours and hours and hours are things that we do for money and so often it is jobs in factories canner you know canning um typing so dolphin in the art is a problem and holding here we describe it as awkward positions um just something that is is continuously irritating it's stimulating a particular um muscle or set of muscles and not challenging another set of muscles for balance um there's an impingement on the blood supply the nerves get damaged the tendons get irritated sometimes just improving the ergonomics that's what those wrist pads are about to help put the hands in a better position for tightening some people like to split keyboard and there can be you know improvements to factory setups so that people don't have to do exactly the same movement or can do it in a way that that's not damaging to their joints so carpal tunnel as I mentioned um the tunnel that's being referred to is this retinaculum there's there's um strip of connective tissue that helps keep all the tendons nerves and blood vessels kind of in place and you get inflammation going through this tunnel sensory findings there's pain and tingling um numbness sometimes in the hand and then the motor finding there's weakness and abduction that's moving the the thumb out and moving on um some things to consider with musculoskeletal system and kids fractures of bones are common with kids um not as common as you would think given the number of times that they fall but um kids fall a lot and so we do have we do see fractures uh bending uh green stick fractures that is a fracture that doesn't go all the way through um because the the periosteum is is thick um and there's there's more flexibility that the bones are not completely mineralized yet um and so they provide a certain amount of flexibility they have the collagen in place um they just haven't completely mineralized yet the good news is that healing happens faster in kids than it does in adults so what would take six to eight weeks and an adult might take four to six weeks right genetic disorders it's not that they that people outgrow the genetic disorders it's just that they're diagnosed typically diagnosed in childhood because they have these severe consequences so one genetic disorder that we've already talked about in this class is muscular dystrophy this is an x-linked recessive that means the gene that codes for the protein involved that Gene occurs on the X chromosome and so for an individual to show the disorder males only need to inherit one defective copy females would need to inherit two defective copies of this Gene um so in any case um the person who has this disorder they have uh a gene that is defective for a protein called the strofen It's A protein that helps to Anchor the actin and the myosin in place in a muscle cell so I'm just quickly remind you actin and myosin have to hold on to each other we've got the tropomyosin wrapped around the myosin the troponin is what binds the calcium ions to roll the thing out of the way and that allows the actin and myosin to hold on to each other if that is not anchored to the cell membrane to the sarcolemma by this protein dystrophin the the muscle can't work it can't contract effectively um the the version of muscular dystrophy that I think we spoke about in class was duchesne's muscular dystrophy this is the more severe version of it um and can lead to symptoms earlier and can lead to death earlier um the folks who were diagnosed with the chains muscular dystrophy are making it to adulthood now um this used to be a progression to death in childhood and there's other versions of this there's a Becker muscular dystrophy in that case the dystrophin is abnormal but still somewhat functional and so as you can imagine the symptoms are not as severe as with duchesne's muscular dystrophy um a second genetic disorder I'm going to mention just in passing um the first one related to the muscle tissue the second one relates to the Bone tissue so osteogenesis imperfecta this is also known as brittle bone disease it's an autosomal dominant so it'll affect males and females equally frequently the protein the gene that let me rephrase that the mutation is in a gene that codes for collagen collagen is an important part of that extracellular Matrix in the bone and this abnormal collagen results in these really brittle bones and so kids babies um have bones broken and initially it may appear like a case of child abuse but it's not it's just regular handling of the baby is resulting in broken bones nowadays we have a genetic test for this disorder um there is no treatment for this really except now since we know what the problem is we know to focus energy on helping the child to develop bone strength bye guess what physical activity so with physical therapy improving the strength of the muscle helps to stabilize the skeleton but also helps the body to get the signal that this bone needs to be mineralized needs to be strengthened okay and now we are shifting gears to older patients gerontological consideration for musculoskeletal aging is associated with loss of bone mass uh the osteoporosis is where the bone have appear to have pores now this is normal spongy bone you know it has these big openings but that they're supposed to be there that these you know weird towers of bone but then if you look at osteoporotic bone you can see that they have more pores this is because the osteoclasts are really active and the osteoblasts are less active so there's not this balance so the osteoclasts are doing what they're supposed to do which is breakdown bone but they're not being counteracted by osteoblasts putting down more Matrix it turns out that bone loss accelerates as the steroid hormones decrease so a loss of estrogen loss of testosterone it seems to be the problem seems to be that in the presence of estrogen and testosterone the osteoclasts do a little bit of breakdown and then they die and as estrogen and testosterone levels go down the osteoclasts you know break down a little bit of bone and then they break down a little bit more bone so in females um there's a faster accelerate there's acceleration of bone loss after menopause because of the big drop off in estrogen levels in males there's also a drop off in testosterone with age but it's not as precipitous as it is for Phoenix um how to assess this we do it through bone a measurement called bone mineral density and it's done with dual energy x-ray absolute I can't say a dexa scan um and the reason it has to be done that way is because just checking the blood level of calcium is not necessarily informative for bone density because remember calcium is required for uh heart muscle contraction that's required for nerve signaling it's so the body is very good at maintaining enough calcium in the blood and will sacrifice the bone in the interest of keeping enough calcium in the blood to do those other jobs and so that's why the blood level of calcium isn't necessarily informative all right now both some amount of bone loss can be counteracted by enhanced physical activity the more uh where when the more weight-bearing exercise the person does the more the body gets the signal hey osteoblasts you need to do your thing you need to put down more minerals in the bones okay now let's take a look at what happens with muscle mass we also see a loss of muscle mass with aging this is referred to as sarcopenia Sarco is muscle and pineas uh poverty um so this is one component of the clinical Frailty indexes there's lots of factors that contribute to sarcopenia loss of different parts of the muscles muscle cells loss of innervation here's another really important point some amount of this sarcopenia may be counteracted with enhanced physical activity so at the very time that our patients are losing muscle mass losing bone density may not feel like they're the strongest they've ever been that's when they need the physical activity because it's going to help counteract some of this you know loss that we associate with aging so Empower your patients they can help prevent some of these problems all right now let's take a look at joint disorders that are often associated with age these are the arthritis and so itis inflammation arthro refers to the joints the most common one is osteoarthritis and but we'll mention a couple of others uh Gaudi arthritis also known as gout and rheumatoid arthritis so osteoarthritis What's Happening Here is we're losing articular cartilage we're losing that that um that other tissue that covers the ends of the bones where they articulate um and so there's swelling um there's these bony Spurs that can start to form when the bones are hitting other bones instead of just you know the con the cartilage gently tapping in got bone on bone and the bones responds by starting to grow more bone it's not beautiful the Obesity is a risk factor because of the extra stress on the bones just carrying around this extra weight that we carry is harder on our joints also if there's been a prior injury to that joint that's a risk factor for developing arthritis in that joint lifestyle recommendations again this is the patients are experiencing discomfort and may not want to use these joints and yet by strengthening the muscles around those joints it helps to stabilize the joint and actually may help control some of the pain that the patients are feeling um also weight loss will help to decrease the stress on the joints and that's why that's being recommended it's not to beat up the patients but again to empower the patients for them to know that there is something that can be done about some of this discomfort uh just a flow chart some pretty colors some of the same stuff I already talked about all right gouty arthritis or gout Um this can happen in younger patients as well uh it's an imbalance of uric acid production and uric acid excretion through the kidneys uric acid is normal we have it in our bodies it's a natural waste product from metabolizing purines purines you may remember are the nucleotides that have two ring structures let's see it's the adenine and adenine and guanine and DNA it's also the a of ATP um so those are the purines so clearly all of us have purines not everybody develops gout however what we see in somebody with gout is of course elevated level of uric acid but you'll see that sometimes in other patients that don't have gout but so along with the elevated levels of uric acid we often associate dehydration with this low temperature curiously which may actually help explain why one of the first places that people experience pain from gout is in the big toe it's about as far away as you can get from the the rest of the body and is you know maybe a little bit cooler than the rest of the body and they allow these crystals to form once the crystals start to form it's easier for more uric acid to crystallize on those crystals the joints um get lots and lots of inflammation and swelling incredible amounts of pain and all you know remember blood vessels vasodilate more blood to the area they so we get redness in the area because we can see the the hemoglobin through the skin um and then the pain the release of the prostaglandins that are tickling the pain receptors just awful samples of synovial fluid show that there are crystals in there and it's also possible for the crystals to be deposited in the skin these are visible it's tofi especially around the ears places where we have cartilage allows the the tophide to the crystals to be deposited uh one suggestion is to increase water intake help to avoid the dehydration so it helps to dilute the uric acid and helps to flush it out which help may help avoid development of uric acid kidney stones which sometimes happens with patients with gout one more kind of arthritis um rheumatoid arthritis this one is an inflammatory joint disease so it's involving the the immune system rheumatoid arthritis may occur in younger patients as well it's it's not as common but it can happen in younger patients it tends to attack the larger joints so it's an autoimmune disorder uh leads to chronic inflammation of the joints which of course is going to lead to pain and it leads to this overactivity of the osteoclasts so breaking down the bone tissue and that leads to the changing shape of the bones the the deformities that we see in the hands and the feet uh it's diagnosed of course with local symptoms you know pain inflammation but also symptoms of systemic inflammation so blood markers of inflammation and then another kind of inflammatory joint disease uh this is a spondyloarthritis the most common form is Ankylosing Spondylitis ankylosing means fusing if you're fans of dinosaurs ankylosaur as the fused blizzard yeah all right so let me remind you about the the skeleton um you saw this diagram before do you see the part that's shown in kind of a darker peach colored uh this is the so-called axial skeleton it's the kind of the central part of the body the head uh the vertebral column the ribs I think of this as the part of the skeleton we have in common with snakes so that's uh axial skeleton the rest of the skeleton the stuff that helps to Anchor the arms and legs that's all appendicular skeleton so this primarily affects the axial skeleton and we've already talked about the the vertebrae and how they articulate here at the body but they also articulated these other facets here these are synovial joints and so there should be lots and lots of movement and instead we get all this inflammation and then fusing here that's where the ankylosing comes from you're fusing the bone so the patient is completely losing mobility in these parts of the bone parts of the the vertebral column which leads to a lot of discomfort of course on the inflammation bony overgrowth so the fusion of the bones oh this can also affect remember I said axial skeleton is the central part it also affects here where the axial skeleton joins the appendicular skeleton it's known as the sacroiliac joint this is the sacrum and this is the ilium so the s-i joint is also affected and this again is an inflammatory joint disease so there would be markers of inflammation for this one too and that is the end of musculoskeletal system have a great week