Chapter 23: Musculoskeletal System

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Welcome to this deep dive.

If you're listening to this right now, you're likely gearing up for a major exam or maybe you're stepping onto the clinical floor tomorrow morning.

Yeah, and you probably just need a serious refresher.

Exactly.

We're treating today's session as a last minute lecture.

It's designed specifically to help you conquer chapter 23 on the musculoskeletal system from your physical examination and health assessment textbook.

Right.

And our mission today is straightforward.

We are going to help you master this assessment by logically connecting foundational anatomy to your patient interview skills.

And then linking those physical exam techniques directly to your clinical reasoning.

By the not just what to look for, but why it matters for your patient's safety.

And to make sure you get exactly what you need to pass, we are keeping our sources strictly to that ninth edition textbook chapter.

There is zero outside noise today.

Everything we discuss is grounded right in the text.

I'm joined by our resident clinical guide who is going to help us synthesize all this dense information into knowledge you can actually use at the bedside.

Okay, let's unpack this.

Start with the foundational concepts.

Well, let's do it.

When we look at the whole system, it's doing five huge jobs behind the scenes, right?

It really is the framework of the house.

I mean, we often think of the MSK system purely in terms of movement, but it's doing so much more.

Yes.

We need it for support to stand erect and obviously for movement.

But it also functions as a physical vault to encase and protect inner vital organs like the brain, the spinal cord and the heart.

Fourth, it's a manufacturing center.

It produces red blood cells, white blood cells and platelets in the bone marrow.

That is a continuous process called hematopoiesis.

And finally, it acts as a storage reservoir for essential minerals, specifically your body's calcium and phosphorus.

Structurally, we are talking about 206 bones in the adult body,

but bones on their own are just rigid sticks.

Right.

They can't do much without joints.

The joint or articulation is the functional unit of the whole system.

There are three types of joints you're going to encounter.

First, you have fibrous joints.

Think of a newborn skull eventually knitting together into these unyielding fibrous seams.

The brain doesn't need flexibility.

It needs a protective vault.

So those bones are united by fibrous tissue and become completely immovable.

Second, we have cartilaginous joints.

These are separated by fibrocartilaginous discs and are only slightly movable.

If you picture the vertebrae in your spine, they give you just enough flex to bend over without compromising the spinal cord.

And the third type is where all the clinical action happens, the synovial joints.

These are freely movable because the bones are separated and enclosed in a dedicated joint cavity.

The textbook uses a fantastic mental image here.

Yeah.

The cavity is lined with a synovial membrane that secretes synovial fluid.

Just like grease on gears, this fluid allows the cartilage -covered bones to slide smoothly against each other without grinding.

What's fascinating here is how the structure of each joint dictates its specific clinical vulnerabilities.

In these synovial joints, you have supporting structures keeping that gearbox intact.

You have ligaments, which are tough fibrous bands running directly from bone to bone.

They strengthen the joint and physically block undesirable movement.

And then you have bursa.

Think of a bursa as a tiny enclosed sack filled with viscous synovial fluid, strategically placed in areas of high friction.

Like the subacromial bursa in the shoulder or the prepatellar bursa in the knee, they sit there helping muscles and tendons glide over the hard bone.

Now, if you are taking notes, let's trace the key anatomical landmarks.

Because knowing where things are is half the battle when you walk into a patient's room.

Let's visualize the spine.

It's a vertical column of 33 connecting bones, seven cervical in the neck, 12 thoracic behind the chest, five lumbar in the lower back, five sacral, and three or four caesigial vertebrae at the tailbone.

You absolutely need to know your surface landmarks so you can orient yourself during an assessment.

Let's map it out.

If you feel the prominent bumps right at the base of the neck, those are the spinous processes of C7 and T1.

And if you run your hands down to the inferior angle of the scapula, that normally aligns with the inner space between T7 and T8.

Now imagine a line connecting the highest point on each of the patient's iliac crests.

That line crosses exactly at L4.

And a line joining the two symmetric dimples overlying the posterior superior iliac spines will cross the sacrum.

Between all these vertebrae are the intervertebral discs, which make up a quarter of the entire length of the column.

Inside each of those discs is the nucleus pulposus.

The text describes this as a soft, semi -fluid material with the consistency of toothpaste.

These discs are your body's shock absorbers.

As the spine moves, the elasticity allows compression on one side and expansion on the other.

But consider what happens when a patient lifts something too heavy with poor form.

The compression

the disc ruptures, and that toothpaste -like nucleus pulposus herniates out.

It pushes right into the spinal nerves, which causes severe radiating pain.

That is a brilliant way to visualize a herniated disc.

Let's move to the limbs and compare two major ball and socket joints, the shoulder and the hip.

They sound similar, but they operate completely differently.

The shoulder, or glenohumeral joint, has immense mobility.

It allows motion on more axes than any other joint in the body.

But because of that extreme mobility, it sacrifices structural stability.

It relies heavily on a specific group of muscles and tendons to hold it together.

The rotator cuff, made up of the assets muscles, supraspinatus, infraspinatus, teres minor, and subscapularis.

Compare that mechanical setup to the hip.

The hip is also a ball and socket joint, but has a much tighter range of motion.

It requires incredible stability for its weight -bearing function.

So instead of relying mostly on muscles like the shoulder does, the hip features a very deep insertion of the head of the femur into the acetabulum.

It is a deep socket supported by powerful muscles, making it highly stable.

And then we have the knee.

It is the largest and most complex joint in the body.

It is essentially a hinge joint, but unlike the hip, there is no overlying fat or heavy muscle mass to stabilize it.

It relies entirely on ligaments.

The cruciate ligaments criss -crossing inside the knee, and the collateral ligaments on the sides,

along with the medial and lateral monephi, which act as cartilaginous cushions for the tibia and femur.

Because it lacks that muscle or fat stabilization,

the knee is incredibly vulnerable to mechanical injury.

That foundation of structure perfectly sets up your subjective data collection.

When you walk into the room tomorrow and begin the patient interview, the anatomy we just reviewed tells you exactly what clues to listen for.

Right.

If a patient complains of joint pain, we don't just write knee hurts on their chart.

The moment they finish talking, your clinical reasoning begins.

You have to differentiate the cause based on their specific history.

And the timing of the pain is your best diagnostic tool.

Take rheumatoid arthritis versus osteoarthritis.

The timing is completely flipped.

The pain of rheumatoid arthritis, or RA, is typically worse in the morning when the patient first wakes up.

Conversely, osteoarthritis, or OA pain, usually gets worse later in the day after they have been using the joint.

And if a patient had tendonitis, the pain is worse in the morning but actually improves throughout the day as they move around.

Wait, let me make sure I have this right.

Normally, if I have a sore joint moving, it hurts.

But you're saying with rheumatoid arthritis, moving actually makes it feel better.

Why does that happen?

It seems completely counterintuitive, but it's a massive differentiator.

RA is a systemic inflammatory disease.

When the patient is sleeping and still, inflammatory fluid pools in the joint, causing extreme stiffness.

Ah, so when they start moving, it helps circulate that fluid out of the joint space, which decreases the stiffness and pain.

Precisely.

With OA, it's a mechanical wear and tear issue.

So using the joint literally grinds it more, increasing the pain.

That makes so much sense.

We also need to get specific based on the joint involved.

Let's imagine a triage scenario.

A patient comes into the ER reporting a knee injury.

We need to evaluate if they require an x -ray.

And you shouldn't just guess.

The text specifically highlights the Ottawa Knee Rules for this.

The Ottawa Knee Rules are an evidence -based clinical tool.

You need an x -ray if a patient with direct knee trauma meets any of these criteria.

First, they cannot flex their knee to 90 degrees.

Second, they are unable to bear weight for even four steps.

Third, they have isolated pain right at the head of the fibula, or the patella.

Or fourth, they are over the age of 55.

If any of those are present, send them to imaging.

We also have to listen closely to how they describe pain in the muscles versus the bones.

Muscle pain, or myalgia, is usually felt as a cramping or aching sensation, and can sometimes just be a secondary symptom from a viral illness.

But if your patient says, my calf hurts incredibly badly when I walk to the mailbox, but the pain completely vanishes when I sit down to rest, that suggests intermittent claudication.

That is a blood flow issue, not a simple muscle cramp.

Similarly, pay attention to how they describe bone pain.

Bone pain usually feels dull, deep, and is oddly unrelated to movement.

A fracture, however, produces a sharp pain that actively and predictably increases the second they try to move the affected limb.

Beyond just locating the pain, we have to ask about their functional assessment.

Does this musculoskeletal problem limit their activities of daily living, or ADLs?

Are they struggling with bathing, toileting, or dressing?

This screens for the safety of independent living and determines if we need to advocate for home health services.

That is the essence of patient -centered care.

You also need to ask about occupational hazards.

Do they do heavy, repetitive lifting?

What medications are they taking?

Are they swallowing handfuls of NSAIDs for joint pain, which puts them at risk for a GI bleed?

Are they taking bisphosphonates?

And speaking of bone health, if you are treating a female patient who is 65 or older, you need to know the evidence -based screening guideline.

The US government recommends a low -dose x -ray called a DXA scan to screen for osteoporosis.

So, their subjective history points to an issue.

The moment the interview wraps up, your objective exam begins.

And there is a golden rule here.

There is a very strict sequence for this physical exam.

Inspection, palpation, range of motion, and muscle testing.

Do not mix up this order.

During inspection and palpation, you are always comparing corresponding pair joints for symmetry.

You look at the right knee and the left knee.

You're looking for swelling, deformity, or skin changes.

When you palpate, normally the synovial membrane is completely imperceptible.

But if it's inflamed and thickened, it alters the texture.

You'll feel it.

It won't feel like fluid.

A thickened synovial membrane feels doughy or boggy to the touch.

Once you've palpated, you move to range of motion, or ROM.

Finding a limitation in ROM is the most sensitive sign of joint disease.

But clinically, you have to distinguish between articular and extraarticular disease based on what you see.

Think of extraarticular disease like a frayed wire on the outside of a machine, whereas articular diseases rust inside the main gearbox.

Articular disease means the issue is inside the joint capsule, like arthritis.

Because the whole gearbox is rusted, it produces swelling and tenderness around the entire joint, and limits all planes of range of motion, whether the patient is moving it actively or you are moving it passively for them.

Extraarticular disease means the injury is to a specific tendon, ligament, or nerve outside the main capsule.

Because it's a specific frayed wire, it produces targeted swelling to one isolated spot and affects only specific planes of motion, especially during active voluntary movement when they engage that specific tendon.

We've all had that moment as a student where we ask a patient to bend their knee, we hear a loud crack, and we panic thinking we just broke them.

But we need to clarify what we are hearing.

You might notice crepitation.

Crepitation is an audible and palpable crunching or grating sound that occurs when the articular surfaces in the joints are roughened, like with rheumatoid arthritis.

Do not confuse this with a normal, discreet crack or pop you might hear when a healthy tendon or ligament slips over a bone.

A quick crack is fine.

A sustained, crunching crepitation is pathology.

After range of motion, we do muscle testing.

You ask the person to flex and hold as you apply an opposing force.

Muscle strength should be equal bilaterally and fully resist your force.

We grade this on a scale from 0 to 5, and you need to internalize what these numbers actually mean for your patient's mobility.

Grade 5 is full ROM against gravity with full resistance.

That is 100 % normal.

Grade 4 is full ROM against gravity, but with only some resistance.

Think of grade 3 as your clinical tipping point.

That is the baseline where a patient can move against gravity.

Anything below a 3 means they can't even lift their own arm or leg off the bed, which completely changes your care plan for their basic safety.

Grade 2 is full ROM, but only with gravity eliminated, meaning passive motion if you support the limb.

Grade 1 is just a slight muscle contraction, a trace flutter, and grade 0 is absolutely zero contraction.

The text then walks us through special clinical tests.

Let's look at the knee.

If a patient reports a history of trauma, followed by a sensation of the knee locking or giving way, you perform the McMurray test.

You position the patient's supine, hold their heel, and flex the knee and hip.

You rotate the leg in and out to loosen the joint.

Then you externally rotate the leg and push a valgus stress on the knee.

When you apply a valgus stress, imagine trying to gently open a thick book by pushing the knee inward toward the other leg, while pulling the ankle outward.

You hold that stress while slowly extending the knee.

If you hear or feel a physical click, the McMurray test is positive for a torn meniscus.

For the spine, if someone comes in with severe back and leg pain, we use the straight leg raise, or LASIG test.

This maneuver physically stretches the nerve route to help confirm sciatica and herniated nucleus pulposus.

You raise the affected leg just short of the point where it produces pain, and then dorsiflex the foot.

If that reproduces their sciatic pain, it's a positive test.

You also need to know how to measure leg length.

You might have a patient whose legs simply look unequal when they lie down.

To determine if it's true or apparent, you measure.

True leg length is measured between fixed bony points from the anterior superior iliac spine to the medial malleolus.

These should be equal or within one centimeter.

But sometimes true leg length is perfectly equal, yet the legs still look unequal.

That is an apparent leg length discrepancy, which occurs with pelvic obliquity, where the pelvis is tilted.

To check this, you measure from a non -fixed point, like the umbilicus, down to a fixed point, like the medial malleolus.

Here's where it gets really interesting.

When we apply these assessment techniques to different developmental stages of life, the musculoskeletal system is not steric.

It changes dramatically from birth to adulthood.

In infants, by three months gestation, the fetus has formed a scale model of the skeleton made entirely of cartilage.

During succeeding months in utero, this cartilage ossifies into true bone.

So when you are assessing a newborn, you are looking for specific developmental markers that tell you if that process happened correctly.

For the hips, we use the Ortolani sign and the ALICE test to check for developmental dysplasia of the hip, or DDH.

With a dislocated hip, the head of the femur is displaced out of the acetabulum.

First, check for unequal gluteal folds on the back of the legs.

Then, use the ALICE test.

Place the baby's feet flat on the exam table and flex the knees up.

If one knee sits significantly lower than the other, that's a positive ALICE sign, strongly suggesting hip dislocation.

You also meticulously inspect the newborn's hands and spine.

In the hands, you are checking for polydactyly, which is the presence of extra digits, or syndactyly, which is webbing between the digits.

Also note if there is a single palmar crease across the hand, which can be associated with On the back, inspect the entire length of the spine.

If you spot a tuft of hair or a deep dimple in the midline, that might indicate spina bifida.

And do not forget to palpate the clavicles.

The clavicle is the most frequently fractured bone during the birth process.

As you run your fingers over it, it should feel completely smooth without any lumps or grinding crepitus.

Moving into early childhood, parents are often highly anxious about their toddler's leg alignments.

There are two very common conditions to memorize.

First is genuverum.

This is a lateral bowing of the legs, present when there is a space of more than 2 .5 centimeters between the knees when the medial malleoli are touching.

This is totally normal for one year after the child begins walking, and usually resolves without any treatment.

Second is genuvalgum.

This is when there is more than 2 .5 centimeters between the medial malleoli when the knees are touching together.

This occurs normally between 2 and 3 .5 years of age.

I always used to get these mixed up, but the textbook gives a perfect memory trick.

Varum means the knees are far apart.

Valgum means the knees are stuck together like they have gum between them.

Parents also worry about pes planus, or flat feet, and pigeon toes.

You can reassure them that the normal logicudinal arch is often just concealed by a thick fat pad in toddlers, and forefoot adduction causing pigeon toes usually corrects spontaneously as they grow.

But what about sudden injuries?

We hear a lot about nursemaids' elbow in children ages 2 to 4.

What is the actual mechanism of that?

It's a subluxation of the radial head.

It is usually caused by forceful pulling, like an adult suddenly lifting or suspending a child by the hands to swing them or prevent them from falling.

The child will present holding the arm flexed against their body.

They will have an inability to supinate the hand, meaning they can't turn their palm up, and will cry in pain if you attempt to move the elbow.

As children grow into adolescence, their posture changes dramatically.

Kyphosis, a rounding of the upper thoracic back, is very common during adolescence, simply due to poor posture.

And there is scoliosis, a lateral curvature of the spine.

This raises an important clinical point about following current evidence -based practice.

The U .S.

Preventive Services Task Force actually no longer recommends routine screening for asymptomatic teens for idiopathic scoliosis.

The data showed that the harm of unnecessary imaging, unneeded bracing, and the associated psychological effects outweighed the benefits.

However, if structural scoliosis is suspected, meaning there is a fixed curvature that shows a distinct rib hump when the patient bends forward in flexion, practitioners absolutely must evaluate it.

Let's tie all of this into your clinical interpretation and documentation.

Chapter 23 highlights a few specific pathologies in its tables that you should recognize visually.

There's Osgood -Schlader disease, which presents as a painful swelling of the tibial tubercle just below the knee.

It occurs strictly from overuse during puberty's rapid growth spurts.

There is also post -polio muscle atrophy, which you might observe in older patients who survived the severe polio epidemics of the 1940s and 50s.

It typically presents as significant right leg and foot muscle atrophy compared to the left.

And pediatric congenital abnormalities like club foot or talipase equinovirus.

This is a rigid malposition of the foot involving inversion, forefoot adduction, and the foot pointing downward.

Because you are constantly assessing a patient's mobility, patient safety is paramount.

The text literally outlines specific fall prevention guidelines you need to teach your older patients.

You need to encourage building strength with a targeted exercise program, review any of their medications that might cause dizziness, and affect balance.

Ensure their vision and hearing are checked annually and actively safety -proof the home by increasing lighting, installing grab bars in the bathroom, and removing hidden trip hazards like loose throw rugs.

If we connect this to the bigger picture,

proper documentation isn't just busy work or checking boxes.

It dictates the entire trajectory of patient care, insurance coverage, and safety.

The text provides excellent case studies showing how you bridge what the patient says to what you write.

Case 1 is rheumatoid arthritis.

Subjectively, you don't just write joint pain.

You document the specific clues, the patient experiencing morning stiffness lasting up to an hour, and joints feeling warm, swollen, and tender.

Objectively, you document the measurable proof, bilateral swelling, and your assessment of their decreased mobility, leading to a formal nursing assessment of acute pain and decreased physical mobility.

Case 2 is osteoarthritis.

Subjectively, the patient reports bilateral knee pain for two years that actively increases during the working day in a terrifying recent episode where the knee just gave out.

Objectively, you document an inability to flex the hip with the knee straight,

and that their knee flexion standing with support is only 90 degrees and elicits pain.

And case 3 is a pediatric patient.

Subjectively, the parents report a two -year -old boy refusing to use his right arm after being swung by his hands.

Objectively, the child is guarding the right arm, holding it flexed and pronated against the body, and crying out specifically when you attempt to supinate the hand.

That documentation perfectly supports the assessment of radial head subluxation or nursemaid's elbow.

Capturing those precise details, the timing of the pain, the exact degree of range of motion, the specific plane of movement that hurts is what separates a basic assessment from a masterful one.

It completely shifts your perspective.

You aren't just looking at a knee or a shoulder.

You are looking at a lifetime of mechanics playing out right in front of you.

I want to leave you with a final thought to mull over before your exam.

The musculoskeletal system is the ultimate silent record keeper of a patient's life.

Every sport they ever played, every heavy occupational hazard they've endured, every rapid growth spurt they had as a child, it is all written right there into the wear and tear of their bones and joints.

How will understanding this mechanical diary change the way you observe your patients the very second they walk into the room tomorrow?

It really is a powerful way to think about it.

So what does this all mean?

It means you are absolutely ready for your clinicals.

Thank you for studying with the Last Minute Lecture team.

You've got this.