Step 3 · 5–7%

Musculoskeletal System

Back pain, arthritis, rheumatology, injuries and the child who limps.

Back & neck pain

Most back and neck pain needs no imaging and gets better with activity; the questions ask you to spot the red flags, the root level, and the few emergencies that cannot wait.

Rules to know

Acute low back pain under 6 weeks, no red flags → no imaging; stay active, heat, NSAIDs; bed rest slows recovery
Back pain red flags → cancer history, weight loss, fever, IV drug use, major trauma, steroid use, progressive deficit, bladder or bowel change
Saddle numbness, urinary retention or incontinence, bilateral leg symptoms → cauda equina syndrome; emergency MRI and same-day surgical decompression
Back pain in a patient with a cancer history → MRI of the spine; urgent if any neurologic sign
Back pain with fever, IV drug use or recent bacteremia → spinal epidural abscess until excluded; urgent contrast MRI, blood cultures, ESR and CRP
Sciatica without motor deficit → 6 weeks of conservative care; MRI only if pain persists and injection or surgery is being considered
Weak great-toe extension and foot dorsiflexion, numb dorsum of foot → L5 root, usually an L4–L5 disc
Weak plantar flexion, lost ankle reflex, numb lateral foot → S1 root, usually an L5–S1 disc
Weak knee extension, reduced patellar reflex, numb medial shin → L4 root
Disc herniation with progressive weakness, or disabling pain after 6 weeks → surgical referral; discectomy speeds relief
Older adult, leg pain walking, relieved by sitting or leaning forward → lumbar spinal stenosis (pulses normal); PT; MRI if surgery is considered
Older patient with sudden midline back pain after minor strain, point tenderness → vertebral compression fracture; x-ray, analgesia, then osteoporosis evaluation
Compression fracture with a neurologic deficit or suspected tumor → MRI
Under 45, chronic back pain, morning stiffness, better with exercise → axial spondyloarthritis (night pain common); sacroiliac imaging, HLA-B27, CRP
Axial spondyloarthritis → exercise plus full-dose NSAIDs; TNF or IL-17 inhibitor if NSAIDs fail; methotrexate does not help spinal disease
Chronic low back pain over 12 weeks → exercise, PT, CBT, yoga or tai chi; NSAIDs or duloxetine; avoid long-term opioids
Muscle relaxants for back pain → short course for acute spasm only; sedating, avoid in older adults
Acute back pain and work → return early with modified duties; long time off worsens outcomes
Adolescent athlete with back pain on extension (gymnast, lineman) → spondylolysis; x-ray, then MRI or CT; rest from sport, sometimes a brace
Neck pain radiating down the arm, positive Spurling test → cervical radiculopathy; conservative care; MRI for progressive deficit or no improvement by 6 weeks
Weak wrist extension, reduced biceps reflex, numb thumb → C6 root; weak triceps with numb middle finger → C7 root
Older adult with clumsy hands, unsteady gait, hyperreflexia, Hoffmann sign → cervical myelopathy; cervical MRI and surgical referral
Alert, sober neck-trauma patient, no midline tenderness, deficit or distracting injury → clear the neck clinically, no imaging
Adult neck trauma that needs imaging → CT of the cervical spine, not plain films
Long-standing rheumatoid arthritis with neck pain or myelopathy signs → imaging for atlantoaxial instability before intubation
Whiplash without fracture → early movement and normal activity; a soft collar slows recovery

Traps that cost points

Ordering an MRI for two weeks of back pain without red flags→ Early imaging finds incidental disc bulges, drives procedures and does not speed recovery; reassure and reassess at 4–6 weeks.
Prescribing bed rest for acute back pain→ Rest slows recovery; advise staying active within comfort and returning to work with modified duties.
Booking an outpatient MRI for new saddle numbness and urinary retention→ That is cauda equina until proven otherwise; emergency MRI and surgical decompression the same day.
Calling sudden severe back pain with hypotension in an older smoker a muscle strain→ Think ruptured abdominal aortic aneurysm; bedside ultrasound or CT and vascular surgery now.
Starting long-term opioids for chronic low back pain→ Benefit is small and risks are large; use exercise, PT, CBT, NSAIDs or duloxetine.
Ordering plain cervical films after neck trauma in an adult who needs imaging→ CT is far more sensitive for fractures; plain films miss injuries.
Adding methotrexate for inflammatory back pain from ankylosing spondylitis→ It does not help axial disease; after NSAIDs fail, use a TNF or IL-17 inhibitor.
Missing myelopathy by blaming hand clumsiness on arthritis→ Hyperreflexia, a Hoffmann sign or gait change points to cord compression; get a cervical MRI.

Joint pain, arthritis & gout

In the Brain

Tap the hot joint before antibiotics, treat gout flares by comorbidity and lower urate to a target, and start a DMARD early for rheumatoid arthritis.

Rules to know

Hot swollen joint → aspirate before antibiotics: cell count, Gram stain, culture, crystal exam
Synovial WBC above 50,000, mostly neutrophils → septic until proven otherwise (crystals can coexist); 2,000–50,000 inflammatory; under 2,000 noninflammatory
Septic native joint → IV antibiotics plus drainage by needle, arthroscopy or open surgery; vancomycin for gram-positive cocci, add ceftriaxone for gram-negatives or none seen
Young sexually active adult, migratory arthralgia, tenosynovitis, a few pustules → disseminated gonococcal infection; IV ceftriaxone, NAAT from all exposed sites
Painful prosthetic joint with fever or a draining sinus → aspirate and refer to orthopedics; hold antibiotics until cultures if stable
Gout flare → colchicine within 36 hours (1.2 mg, then 0.6 mg an hour later), an NSAID, or a steroid (oral or intra-articular) chosen by comorbidities
Needle-shaped, negatively birefringent crystals → gout; rhomboid, weakly positive birefringent crystals → CPPD (pseudogout)
Serum urate drawn during a flare → may read normal; recheck about 2 weeks after it settles
Tophi, ≥2 flares a year, or gout erosions on x-ray → start urate-lowering therapy
First gout flare plus CKD stage ≥3, urate above 9, or stones → consider urate-lowering therapy
Urate-lowering drug of choice → allopurinol starting at 100 mg daily or less (lower in CKD), titrated until serum urate is under 6 mg/dL
Starting allopurinol → acceptable during a flare; give colchicine, NSAID or low-dose steroid prophylaxis for 3–6 months
Southeast Asian or African American patient starting allopurinol → HLA-B*58:01 test first because of severe skin reaction risk
Allopurinol not tolerated or not reaching target → febuxostat (caution with cardiovascular disease); refractory tophaceous gout → pegloticase after G6PD testing
Gout in a patient on hydrochlorothiazide → switch antihypertensive if feasible; losartan modestly lowers urate
Needs allopurinol while on azathioprine or mercaptopurine → cut the thiopurine dose sharply or avoid the combination (marrow toxicity)
CPPD before age 60 or extensive chondrocalcinosis → check calcium, PTH, iron studies, magnesium, phosphate, TSH
Knee or hip osteoarthritis → exercise, weight loss, topical NSAID for knee and hand; oral NSAID next; intra-articular steroid for flares
Osteoarthritis with failed conservative care and limited function → joint replacement referral; glucosamine and hyaluronic acid are not recommended
Symmetric small-joint swelling over 6 weeks, morning stiffness over an hour → rheumatoid arthritis; RF, anti-CCP, ESR/CRP, hand and foot x-rays
New rheumatoid arthritis → methotrexate with folic acid as the first DMARD; short low-dose steroid bridge only; treat to remission or low activity
Rheumatoid arthritis not at target after 3 months of methotrexate → add a biologic (usually a TNF inhibitor) or triple therapy; JAK inhibitor after TNF failure
Rheumatoid arthritis with splenomegaly and neutropenia → Felty syndrome
Arthritis, conjunctivitis and urethritis weeks after diarrhea or chlamydia → reactive arthritis; test for chlamydia, NSAIDs, treat the infection
Psoriasis plus DIP arthritis, dactylitis, nail pitting → psoriatic arthritis; NSAIDs, methotrexate for peripheral disease, TNF or IL-17 inhibitor if severe
Sudden symmetric hand arthritis in a parent of young children → parvovirus B19; IgM serology; self-limited
Migratory large-joint arthritis weeks after strep pharyngitis, carditis → acute rheumatic fever; penicillin, NSAID, then long-term penicillin prophylaxis

Traps that cost points

Starting antibiotics before aspirating a hot swollen joint→ One dose can sterilize the synovial culture; aspirate first, then treat right away.
Ruling out infection because the fluid shows urate crystals→ Crystals and infection can coexist; a high neutrophil count still needs culture and empiric coverage.
Stopping allopurinol during a gout flare→ Swings in urate prolong flares; continue the dose and treat the flare separately.
Leaving a patient on allopurinol 300 mg without checking urate→ Treat to target: titrate until serum urate is under 6 mg/dL, rechecking every few weeks.
Starting urate-lowering therapy without flare prophylaxis→ Falling urate mobilizes crystals and triggers flares; add colchicine or another agent for 3–6 months.
Giving full-dose azathioprine with allopurinol→ Xanthine oxidase inhibition raises thiopurine levels and causes marrow failure; reduce the dose to about a quarter or choose another drug.
Prescribing glucosamine or hyaluronic acid injections for knee osteoarthritis→ Benefit is not shown; prioritize exercise, weight loss, NSAIDs and steroid injection for flares.
Keeping rheumatoid arthritis on prednisone alone→ Steroids do not stop erosions and cause long-term harm; start methotrexate promptly and taper steroids.

Lupus, vasculitis, myositis & rheumatic drug safety

In the Brain

Match the pattern of organs involved to the disease and its antibody, act fast on the emergencies (giant cell arteritis, renal crisis, lupus nephritis), and monitor the drugs that keep these patients well.

Rules to know

Young woman with rash, arthritis, cytopenias, proteinuria → SLE; ANA screen, then anti-dsDNA and anti-Smith, C3/C4, urinalysis
Every patient with SLE → hydroxychloroquine at ≤5 mg/kg/day unless contraindicated; baseline eye exam, yearly retinal screening after 5 years
Lupus with proteinuria above 0.5 g/day or active sediment → kidney biopsy; class III or IV → steroids plus mycophenolate or cyclophosphamide, add belimumab or voclosporin
Lupus flare activity → rising anti-dsDNA with falling C3 and C4
Lupus planning pregnancy → quiet disease for 6 months, continue hydroxychloroquine, check anti-Ro and antiphospholipid antibodies, low-dose aspirin
Lupus-like illness on hydralazine, procainamide, isoniazid, minocycline or a TNF inhibitor → drug-induced lupus; anti-histone antibodies; stop the drug
Dry eyes, dry mouth, parotid swelling → Sjögren; anti-Ro and anti-La, Schirmer test, lip biopsy if serology negative; watch for lymphoma
Skin thickening above elbows and knees, Raynaud, anti-Scl-70 → diffuse systemic sclerosis; PFTs with DLCO and echo at baseline and yearly
Scleroderma with abrupt hypertension and rising creatinine → scleroderma renal crisis; ACE inhibitor (captopril) titrated up, continued even on dialysis
Limited scleroderma (CREST) with anticentromere antibodies → pulmonary arterial hypertension risk; yearly echo and DLCO
Over 50, stiff aching shoulder and hip girdles, high ESR → polymyalgia rheumatica (strength normal); prednisone 12.5–25 mg daily, slow taper over a year or more
Over 50 with new headache, jaw claudication, scalp tenderness or vision change → giant cell arteritis; high-dose steroids now, then temporal artery biopsy or ultrasound
Proximal weakness, high CK, heliotrope rash, Gottron papules → dermatomyositis; MRI, EMG, biopsy, myositis antibodies; screen for cancer including CT
Statin with muscle aches and normal or mildly high CK → stop, then rechallenge with a lower dose or another statin
Statin with CK above 10 times normal or weakness → stop the statin; check kidney function and urine for myoglobin
Weakness and high CK persisting months after stopping a statin → anti-HMGCR necrotizing myopathy; needs immunosuppression
Proximal weakness with normal CK on long-term steroids → steroid myopathy; taper the dose, exercise
Widespread pain over 3 months, fatigue, poor sleep, normal exam and labs → fibromyalgia; aerobic exercise, CBT, sleep care; duloxetine, pregabalin or amitriptyline
Sinusitis, lung nodules, hematuria with red cell casts, PR3-ANCA → granulomatosis with polyangiitis; biopsy; rituximab plus steroids
Asthma, eosinophilia, mononeuritis, MPO-ANCA → eosinophilic granulomatosis with polyangiitis; steroids, mepolizumab
Mononeuritis multiplex, abdominal pain, hypertension, hepatitis B, lungs spared → polyarteritis nodosa; angiography or biopsy; treat hepatitis B
Child with leg purpura, abdominal pain, arthritis, hematuria → IgA vasculitis; supportive care; follow urinalysis and blood pressure for 6 months
Palpable purpura, arthralgia, low C4, neuropathy, hepatitis C → mixed cryoglobulinemia; treat hepatitis C with direct-acting antivirals
Young woman with arm claudication, unequal arm pressures, weak pulses → Takayasu arteritis; CT or MR angiography; steroids
Recurrent oral and genital ulcers, uveitis, pathergy → Behçet disease; colchicine or apremilast for ulcers, azathioprine or TNF inhibitor for eye disease
Recurrent short fevers with serositis, Mediterranean ancestry → familial Mediterranean fever; daily colchicine prevents attacks and amyloidosis
Methotrexate monitoring → CBC, liver enzymes and creatinine every 2–4 weeks for 3 months, then every 8–12 weeks; folic acid; limit alcohol
Methotrexate with dry cough and dyspnea, mouth ulcers or cytopenias → stop and evaluate; avoid TMP-SMX, reduce in CKD, require contraception
Prednisone ≥2.5 mg daily expected for ≥3 months → calcium, vitamin D, fracture risk assessment with DXA; bisphosphonate if risk is moderate or high
Low-titer positive ANA in a well person → common and nonspecific; no further antibody panels without lupus features

Traps that cost points

Ordering ANA for fatigue and diffuse aches without lupus features→ Low-titer ANA is common in healthy people; test only when the clinical picture fits.
Waiting for the temporal artery biopsy before starting steroids→ Vision loss can be permanent within days; start high-dose steroids now. Biopsy stays positive for 1–2 weeks.
Giving high-dose prednisone to a patient with diffuse scleroderma→ High-dose steroids can precipitate scleroderma renal crisis; use the lowest dose possible and monitor blood pressure.
Stopping the ACE inhibitor in renal crisis because creatinine rises→ The ACE inhibitor is the treatment and improves survival; keep titrating it, even if dialysis is needed.
Prescribing opioids for fibromyalgia→ Opioids do not help and can worsen pain sensitivity; use exercise, CBT, sleep care and duloxetine or pregabalin.
Skipping cancer screening in new dermatomyositis→ Adult dermatomyositis is often paraneoplastic; do age-appropriate screening plus CT, and pelvic imaging in women.
Stopping hydroxychloroquine once lupus is quiet→ Stopping raises flare risk; it is continued long term, with retinal screening.
Prescribing TMP-SMX to a patient on methotrexate→ Both block folate pathways and can cause severe pancytopenia; pick another antibiotic.

Fractures, sports & overuse injuries

In the Brain

Use decision rules to image only when needed, splint the fractures that x-rays miss, catch compartment syndrome early, and know which sprains and overuse injuries just need rehab.

Rules to know

Ankle injury → x-ray only for tenderness at the posterior edge or tip of a malleolus, or inability to take 4 steps
Midfoot injury → x-ray for tenderness at the navicular or fifth metatarsal base, or inability to bear weight
Knee injury → x-ray if age ≥55, isolated patellar or fibular head tenderness, cannot flex to 90°, or cannot bear weight
Snuffbox tenderness after a fall on an outstretched hand, normal x-ray → thumb spica splint, repeat x-ray at 10–14 days or MRI now
Displaced or proximal-pole scaphoid fracture → orthopedic referral for fixation (nonunion and avascular necrosis risk)
Older adult after a fall, shortened and externally rotated leg → hip fracture; x-ray, MRI if negative but suspicion high; surgery within 24–48 hours
After hip fracture repair → early mobilization, VTE prophylaxis, delirium prevention, then osteoporosis treatment
Pain out of proportion and on passive stretch after fracture or crush → compartment syndrome; split the cast, measure pressure, emergency fasciotomy
Pop, quick swelling and instability after a pivot → ACL tear; Lachman test, MRI; reconstruction for active patients
Twisting injury, delayed swelling, locking, joint-line tenderness → meniscal tear; MRI for mechanical symptoms; truly locked knee → arthroscopy
Blow to the outside of the knee, medial pain → MCL sprain; hinged brace and rehab
Knee dislocation, even if already reduced → ankle-brachial index or CT angiography for popliteal artery injury
Overhead shoulder pain, painful arc, weak external rotation → rotator cuff tendinopathy; PT, NSAIDs, subacromial steroid injection
Older adult cannot lift the arm after a fall, drop-arm sign → full-thickness cuff tear; ultrasound or MRI; early surgical referral if active
Painful shoulder with lost active and passive motion in a diabetic → adhesive capsulitis; PT, intra-articular steroid; resolves over 1–3 years
Anterior shoulder dislocation → test axillary nerve sensation over the lateral shoulder; x-ray before and after reduction
Arm held internally rotated after a seizure or electric shock → posterior shoulder dislocation; axillary or scapular Y view
Humeral shaft fracture with wrist drop → radial nerve palsy; splint, usually recovers
Lateral elbow pain with gripping → lateral epicondylitis; activity change, counterforce strap, eccentric exercise; most resolve within a year
Radial wrist pain with thumb motion, positive Finkelstein, new parent → de Quervain tenosynovitis; thumb spica splint, steroid injection
Heel pain with the first steps of the morning → plantar fasciitis; stretching, heel cups, NSAIDs; most improve within a year
Runner with focal bone tenderness and a normal x-ray → stress fracture; MRI, relative rest; screen for low energy intake and menstrual change
Stress fracture at femoral neck, navicular, anterior tibia or proximal fifth metatarsal → high risk; no weight bearing, orthopedic referral
Fifth metatarsal base avulsion → walking boot; Jones fracture at the metaphysis-diaphysis junction → non-weight-bearing cast or fixation
Pop at the back of the heel, positive Thompson test → Achilles rupture; equinus splint and orthopedics; fluoroquinolones and steroids raise risk
Ankle sprain with negative or no x-ray → brace, early weight bearing, balance exercises; casting slows recovery
Open fracture → IV cefazolin within an hour, tetanus update, sterile dressing, operative debridement
Pelvic fracture with hypotension → pelvic binder and transfusion, then angioembolization or preperitoneal packing
Long-bone fracture, then hypoxemia, confusion, petechiae 1–3 days later → fat embolism; supportive care; early fixation lowers risk
Fingertip droops after a jammed finger → mallet finger; continuous DIP extension splint for 6–8 weeks
Swollen olecranon or prepatellar bursa → aspirate if warm or red; septic (usually S aureus) needs antibiotics, aseptic needs compression and rest

Traps that cost points

Ordering an ankle x-ray for every inversion sprain→ Apply the ankle rules; without bony tenderness at the key sites and with weight bearing intact, films are not needed.
Sending home snuffbox tenderness with a normal x-ray and no splint→ Early scaphoid fractures hide on films and can go on to avascular necrosis; immobilize and reimage.
Waiting for pulselessness before diagnosing compartment syndrome→ Pulses vanish late; pain with passive stretch and pain out of proportion are early signs that need fasciotomy.
Elevating a limb high above the heart for suspected compartment syndrome→ Elevation lowers perfusion pressure; keep it at heart level and release all dressings.
Trusting palpable foot pulses after a knee dislocation→ Intimal injury can be present with pulses; measure the ankle-brachial index or obtain CT angiography.
Keeping a painful shoulder in a sling for weeks→ Immobilization leads to adhesive capsulitis; start range-of-motion exercises early.
Casting a simple ankle sprain→ Functional bracing with early weight bearing gives faster recovery and less stiffness.
Delaying hip fracture surgery for extensive preoperative testing→ Surgery after 48 hours raises mortality; optimize quickly and operate.

Bone infection, necrotizing infection & bone tumors

In the Brain

Prove osteomyelitis with bone, operate first on necrotizing infection, look for a primary cancer behind most bone lesions, and send suspected sarcoma to the team that will treat it.

Rules to know

Diabetic foot ulcer probing to bone or larger than 2 cm² → osteomyelitis likely; plain x-ray, then MRI if unclear; high ESR supports it
Suspected osteomyelitis, stable patient → bone biopsy with culture before antibiotics; swabs of the ulcer surface mislead
Diabetic foot osteomyelitis without bone resection → about 6 weeks of antibiotics; shorter if all infected bone is removed
Mildly infected diabetic foot → oral cephalexin or similar; moderate or severe → IV broad coverage including MRSA and gram-negatives
Diabetic foot ulcer without signs of infection → wound care and offloading, no antibiotics
Diabetic foot with gas, abscess, necrosis or rapidly spreading infection → urgent surgical debridement
Child with fever, limp and point bone tenderness → acute hematogenous osteomyelitis; blood cultures, MRI; cefazolin, or clindamycin or vancomycin by local MRSA rates
Back pain, fever, high ESR and CRP → vertebral osteomyelitis or discitis; contrast MRI, blood cultures, CT-guided biopsy if cultures negative; 6 weeks of therapy
Stable patient with suspected vertebral osteomyelitis → hold antibiotics until blood cultures or biopsy are obtained
Slow thoracic vertebral infection in someone from a TB-endemic area → tuberculous spondylitis; biopsy for AFB smear and culture
Osteomyelitis in sickle cell disease → Salmonella as well as S aureus; cover both
Nail through a sneaker sole, later foot bone infection → Pseudomonas; debridement plus antipseudomonal antibiotic
Pain out of proportion, fast-spreading redness, bullae, crepitus, toxic appearance → necrotizing fasciitis; emergency surgery plus vancomycin, piperacillin-tazobactam and clindamycin
Suspected necrotizing soft-tissue infection → imaging must never delay operative exploration
Saltwater wound or raw oysters in liver disease, rapid bullous infection → Vibrio vulnificus; doxycycline plus ceftriaxone or ceftazidime, debridement
Perineal pain, swelling and crepitus in a diabetic man → Fournier gangrene; emergency debridement and broad antibiotics
Deep wound, crepitus, bronze skin, gas on x-ray → clostridial myonecrosis; debridement, penicillin plus clindamycin
Adult with a new destructive bone lesion → metastasis is most likely (breast, prostate, lung, kidney, thyroid); CT chest/abdomen/pelvis, SPEP, PSA, then biopsy
Bone scan → finds blastic metastases (prostate, breast); misses myeloma and purely lytic lesions
Large painful lytic lesion in a weight-bearing bone → high fracture risk; prophylactic fixation, then radiation
Painful bone metastases → external beam radiation, often one fraction; bisphosphonate or denosumab to reduce skeletal events
Teen with a painful mass near the knee, sunburst periosteal reaction → osteosarcoma (Codman triangle); MRI, chest CT, biopsy by the treating sarcoma team
Child with a diaphyseal mass, onion-skin periosteal reaction, fever → Ewing sarcoma; chemotherapy plus surgery or radiation
Young person with night bone pain relieved by NSAIDs, small lucent nidus → osteoid osteoma; NSAIDs or radiofrequency ablation
Soap-bubble lytic lesion at a long-bone end, young adult → giant cell tumor (ages 20–40); curettage
Incidental enchondroma in a hand bone → observe; a painful or growing cartilage lesion in an adult long bone → think chondrosarcoma
Soft-tissue mass deep or over 5 cm, or enlarging → MRI, then biopsy at a sarcoma center; no excision in the office
Groin pain with steroid use, alcohol or sickle cell, normal x-ray → avascular necrosis of the femoral head; MRI; core decompression early, arthroplasty after collapse
Chronic osteomyelitis with a sinus tract that changes or bleeds → biopsy for squamous cell carcinoma

Traps that cost points

Culturing a swab from the surface of a diabetic ulcer→ Surface swabs grow colonizers; culture bone or deep tissue to guide therapy.
Starting empiric antibiotics in a stable patient before a vertebral biopsy→ Prior antibiotics lower culture yield and lead to long blind courses; obtain cultures first unless septic or with neurologic deficit.
Sending a suspected necrotizing infection for MRI before calling surgery→ Delay increases mortality; surgical exploration is both diagnosis and treatment.
Giving antibiotics for every diabetic foot ulcer→ Uninfected ulcers do not heal faster with antibiotics; use offloading, debridement and glucose control.
Treating a new bone lesion in an older adult as a primary bone tumor→ Metastasis and myeloma are far more common; look for the primary cancer before biopsy.
Having a nontreating surgeon biopsy a suspected sarcoma→ A poorly placed biopsy tract can contaminate tissue and cost the limb; refer to the sarcoma center first.
Using a normal plain film to exclude early avascular necrosis→ X-rays stay normal until collapse; MRI detects early disease when joint-saving treatment still works.
Covering only staphylococci for osteomyelitis in sickle cell disease→ Salmonella is a frequent cause; include coverage such as a third-generation cephalosporin or fluoroquinolone.

Pediatric orthopedics & abuse fractures

In the Brain

Check the hip in every limping child, separate transient synovitis from a septic hip, reassure about normal variants, and recognize the fractures that point to abuse.

Rules to know

Newborn with a positive Ortolani or Barlow test → refer to pediatric orthopedics; Pavlik harness
Normal newborn hip exam but breech or family history of DDH → hip ultrasound at about 6 weeks of age
Infant over 4–6 months, limited hip abduction or unequal knee heights → hip x-ray, since ultrasound is no longer reliable
Obese teen, limp, knee or hip pain, thigh rotates out on flexion → SCFE; AP and frog-leg x-rays of both hips
SCFE confirmed → no weight bearing and urgent surgical pinning in situ; watch the other hip
Boy aged 4–8, mild limp, limited abduction and internal rotation → Legg-Calvé-Perthes; x-ray, MRI if early films are normal
Child with knee pain → examine the hip, because hip disease refers pain to the knee
Well child limping after a viral illness, little or no fever → transient synovitis; NSAIDs, rest, recheck in a few days
Febrile child refusing to bear weight, high ESR and WBC → septic hip likely (fever over 38.5 °C, ESR above 40, WBC above 12,000); ultrasound, urgent aspiration, washout
Adolescent athlete with a painful, swollen tibial tubercle → Osgood-Schlatter; relative rest, ice, NSAIDs, stretching; resolves with growth
Toddler lifted by the hand, now holds the arm limp and pronated → radial head subluxation; reduce by hyperpronation or supination-flexion, no x-ray
Child with a swollen elbow after falling on an outstretched hand → supracondylar fracture; check radial pulse and median nerve; displaced → urgent orthopedics
Adolescent with a rib hump on forward bending → scoliometer; standing spine x-ray if the reading is 7° or more
Idiopathic scoliosis while still growing → Cobb 25–40° → brace; 45–50° or more → surgical referral
Painful scoliosis, rapid progression, left thoracic curve or neurologic signs → spine MRI for tumor or syrinx
Posterior rib, metaphyseal corner, multiple-age, or pre-walking fractures → suspect abuse; skeletal survey if under 2, report
Suspected abuse in an infant under 6 months → add head imaging, dilated eye exam, liver enzymes and lipase; examine siblings too
Many fractures with blue sclerae, hearing loss, brittle teeth → osteogenesis imperfecta, an abuse mimic
Walking toddler, minor fall, nondisplaced spiral tibial fracture → toddler fracture; boot or cast; not suspicious by itself
Point tenderness over a growth plate with a normal x-ray → treat as Salter-Harris I; splint and recheck; types III–V need orthopedics
In-toeing toddler (metatarsus adductus, tibial torsion, femoral anteversion) → reassure; most resolve without braces or special shoes
Bowed legs until age 2, knock-knees at ages 3–7 → physiologic; severe, one-sided or persistent → x-ray, rickets labs, consider Blount disease
Clubfoot at birth → serial Ponseti casting in the first weeks, Achilles tenotomy, then bracing
Arthritis over 6 weeks in a child under 16 → juvenile idiopathic arthritis; ANA-positive oligoarticular disease needs slit-lamp exams every 3 months
Adolescent with knee pain, catching and effusion → osteochondritis dissecans; tunnel-view x-ray and MRI

Traps that cost points

Ultrasound screening of every newborn hip in the first weeks→ Normal laxity before 4–6 weeks gives false positives; examine every baby and image only risk factors or abnormal exams.
Ordering only a knee x-ray for an obese teen with knee pain and a limp→ SCFE refers pain to the knee; examine the hip and order AP and frog-leg hip films.
Letting a child with SCFE walk out on the leg→ Weight bearing can displace the slip and cause avascular necrosis; no weight bearing until surgery.
Calling a febrile child who will not bear weight transient synovitis→ Fever, high ESR, high WBC and refusal to bear weight point to a septic hip; aspirate urgently.
Getting x-rays before reducing a classic pulled elbow→ With a typical pulling story and no swelling, reduce first; image only if function does not return.
Accepting a fall from a couch as the cause of a femur fracture in a 4-month-old→ Infants who cannot walk rarely break a femur by accident; skeletal survey and a report to child protection.
Prescribing braces or special shoes for toddler in-toeing→ Most cases correct with growth; braces add nothing.
Skipping eye exams in a child with JIA and no eye complaints→ Uveitis is often silent and can cause blindness; scheduled slit-lamp screening is required.