5.1 Musculoskeletal & Neurologic
Key Takeaways
- Musculoskeletal content is roughly 8% of the PANRE and Neurologic content is roughly 5%, so together they account for about 13% of a 240-question exam (about 31 items).
- The Ottawa Ankle and Knee Rules are validated decision tools that reduce unnecessary radiographs; absence of bony tenderness at defined landmarks plus the ability to bear weight makes a clinically significant fracture unlikely.
- Acute gout is confirmed by negatively birefringent, needle-shaped monosodium urate crystals on synovial fluid polarized microscopy; first-line therapy is an NSAID, colchicine, or a corticosteroid.
- Time is brain: for acute ischemic stroke, IV thrombolysis is generally considered within about 4.5 hours of a clearly defined last-known-well time, after hemorrhage is excluded by non-contrast CT.
- Acute low back pain without red flags (no trauma, fever, weight loss, saddle anesthesia, or progressive deficit) is managed conservatively without early imaging in most patients.
Why This Section Matters
The National Commission on Certification of Physician Assistants (NCCPA) PANRE content blueprint allocates approximately 8% to the Musculoskeletal System and 5% to the Neurologic System. On a 240-item exam that is roughly 31 questions combined. PANRE rewards recognition of classic presentations, correct first-line management, and the ability to separate emergencies from conditions that are safely managed conservatively.
This section is organized as two halves: musculoskeletal injury and rheumatology first, then the core neurologic disorders. Each subtopic emphasizes the discriminating feature an item is most likely to test.
Fractures and Sprains
A fracture is a disruption of bony cortex; a sprain is a ligament injury graded I (stretch), II (partial tear), or III (complete tear); a strain is a muscle or tendon injury. The decision that most often appears on exams is whether imaging is required.
The Ottawa Ankle Rules indicate ankle radiographs only if there is pain near the malleoli plus bony tenderness at the posterior edge or tip of either malleolus, or an inability to bear weight for four steps both immediately and in the exam setting. The Ottawa Knee Rule prompts knee films for age 55 or older, isolated patellar tenderness, fibular head tenderness, inability to flex to 90 degrees, or inability to bear weight for four steps. These validated tools have high sensitivity for clinically significant fractures and reduce unnecessary imaging.
High-risk fractures the exam expects you to escalate include scaphoid fracture (anatomic snuffbox tenderness with risk of avascular necrosis; immobilize and re-image even if initial films are negative), open fractures (irrigation, antibiotics, tetanus, urgent orthopedics), and any fracture with neurovascular compromise or signs of compartment syndrome (pain out of proportion, pain with passive stretch).
Low Back Pain
Most acute low back pain is mechanical and self-limited. The clinical priority is screening for red flags that suggest a serious cause.
Low Back Pain Red Flags
| Red Flag | Concern |
|---|---|
| Bowel/bladder dysfunction, saddle anesthesia, bilateral leg weakness | Cauda equina syndrome (surgical emergency) |
| Fever, IV drug use, recent infection | Spinal infection (osteomyelitis, epidural abscess) |
| Unexplained weight loss, history of cancer, night pain | Malignancy or metastasis |
| Major trauma, or minor trauma in osteoporosis/older age | Vertebral compression fracture |
| Progressive neurologic deficit | Significant nerve root or cord compression |
In the absence of red flags, early imaging does not improve outcomes. First-line treatment is patient education, continued activity as tolerated, and non-opioid analgesia such as nonsteroidal anti-inflammatory drugs (NSAIDs). Sciatica from lumbar disc herniation typically follows a dermatomal pattern and is reproduced by the straight-leg raise; most cases improve without surgery.
The Major Arthritides
Distinguishing osteoarthritis (OA), rheumatoid arthritis (RA), and gout is one of the most predictable musculoskeletal item families.
| Feature | Osteoarthritis | Rheumatoid Arthritis | Gout |
|---|---|---|---|
| Pattern | Asymmetric, weight-bearing and distal interphalangeal joints | Symmetric, small joints (MCP, PIP, wrists) | Monoarticular, classically first MTP (podagra) |
| Stiffness | Brief (<30 min), worse with use | Prolonged (>1 hr) morning stiffness | Acute, severe, often nocturnal onset |
| Inflammation | Minimal | Prominent, systemic | Marked during flare |
| Key markers/findings | Heberden and Bouchard nodes; joint-space narrowing, osteophytes | RF and anti-CCP antibodies; erosions on imaging | Negatively birefringent urate crystals; elevated uric acid (may be normal in flare) |
| First-line therapy | Acetaminophen/NSAIDs, exercise, weight loss | DMARDs, especially methotrexate | NSAID, colchicine, or corticosteroid for flare |
MCP = metacarpophalangeal, PIP = proximal interphalangeal, MTP = metatarsophalangeal, RF = rheumatoid factor, anti-CCP = anti-cyclic citrullinated peptide, DMARD = disease-modifying antirheumatic drug.
Gout urate-lowering therapy (for example, allopurinol) is for long-term prevention and should not be started or stopped reactively during an acute flare without concurrent anti-inflammatory coverage. Distinguish gout from pseudogout (calcium pyrophosphate; positively birefringent, rhomboid crystals; chondrocalcinosis on imaging) and from septic arthritis, which must be excluded by arthrocentesis in any acutely hot, swollen joint because a missed joint infection is rapidly destructive.
Common Orthopedic Exam Maneuvers
- Shoulder: empty-can and drop-arm tests assess the rotator cuff (especially supraspinatus); a positive drop-arm suggests a significant tear.
- Knee: Lachman and anterior drawer assess the anterior cruciate ligament; McMurray reproduces meniscal pain with rotation.
- Wrist/hand: Phalen and Tinel signs suggest median nerve compression in carpal tunnel syndrome, which causes numbness in the thumb, index, and middle fingers.
Neurologic Emergencies and Chronic Disorders
Stroke and Transient Ischemic Attack (TIA)
An ischemic stroke results from arterial occlusion; a hemorrhagic stroke from bleeding. A transient ischemic attack (TIA) is a transient neurologic deficit without acute infarction and is a warning of high short-term stroke risk that warrants urgent evaluation.
The immediate study in suspected stroke is a non-contrast head computed tomography (CT) to distinguish ischemic from hemorrhagic stroke before any reperfusion therapy. For acute ischemic stroke, intravenous thrombolysis is generally considered within about 4.5 hours of a clearly established last-known-well time when there are no contraindications; selected large-vessel occlusions may also be eligible for mechanical thrombectomy in an extended window.
Blood pressure is permitted to run higher (permissive hypertension) in ischemic stroke unless thrombolysis is planned. Use a validated scale such as FAST (Face, Arm, Speech, Time) for rapid recognition.
Seizure
Classify seizures as focal (one hemisphere, with or without impaired awareness) or generalized (bilateral from onset, including tonic-clonic and absence). A first unprovoked seizure prompts evaluation for a structural, metabolic, or toxic cause. Status epilepticus (a seizure lasting 5 minutes or more, or recurrent seizures without recovery) is an emergency: protect the airway, check glucose, and give a benzodiazepine first-line, followed by a longer-acting antiseizure medication.
Headache
| Type | Classic Features | First-Line Approach |
|---|---|---|
| Migraine | Unilateral, throbbing, photophobia/phonophobia, nausea, sometimes aura | Triptans/NSAIDs for acute attacks; prophylaxis if frequent |
| Tension-type | Bilateral, band-like, pressing, non-throbbing | Simple analgesics, stress management |
| Cluster | Severe, unilateral, periorbital, autonomic (tearing, rhinorrhea), restless | High-flow oxygen, subcutaneous triptan |
Red-flag (secondary) headaches require urgent imaging or workup: thunderclap onset (subarachnoid hemorrhage), new headache after age 50 with jaw claudication or scalp tenderness (giant cell arteritis — start steroids and check inflammatory markers), fever with neck stiffness (meningitis), or focal deficit/papilledema (mass or elevated intracranial pressure).
Peripheral Neuropathy
Peripheral neuropathy classically causes distal, symmetric, stocking-glove sensory loss; diabetes mellitus is the most common cause in U.S. practice. Evaluate for treatable contributors such as vitamin B12 deficiency, alcohol use, thyroid disease, and medications. Glycemic control is central in diabetic neuropathy; neuropathic pain agents (for example, certain anticonvulsants or SNRIs) target symptoms.
Dementia vs. Delirium
| Feature | Dementia | Delirium |
|---|---|---|
| Onset | Insidious, months to years | Acute, hours to days |
| Course | Slowly progressive, stable day to day | Fluctuating, often worse at night |
| Attention | Relatively preserved early | Markedly impaired (the hallmark) |
| Reversibility | Usually irreversible | Often reversible if cause treated |
Delirium is a medical emergency: identify and treat the underlying cause (infection, medications, metabolic derangement, hypoxia). Alzheimer disease is the most common dementia; abrupt stepwise decline with vascular risk factors suggests vascular dementia.
Multiple Sclerosis and Parkinson Disease
Multiple sclerosis (MS) is a demyelinating disease causing relapsing neurologic deficits separated in time and space (for example, optic neuritis, sensory or motor symptoms); magnetic resonance imaging shows characteristic white-matter lesions. Parkinson disease is a dopaminergic neurodegenerative disorder presenting with the triad of resting tremor, rigidity, and bradykinesia, often with postural instability; levodopa-based therapy is a mainstay of symptom control.
A 52-year-old presents 90 minutes after sudden onset of right arm weakness and slurred speech. Vital signs are stable. After airway and glucose are addressed, which is the most appropriate immediate next step?
A 58-year-old man has an acutely painful, red, swollen first metatarsophalangeal joint that began overnight. Arthrocentesis shows needle-shaped, negatively birefringent crystals and no organisms. Which is the most appropriate initial treatment?
A 70-year-old nursing-home resident develops acute confusion over one day with inattention and a fluctuating course that worsens at night. Which statement best characterizes this presentation?