Eduovisual
Pediatrics (System-Integrated)
Legg-Calve-Perthes disease
— Age 4–8 years is the classic window (range 2–12).
— Boys ~4–5× more often than girls; bilateral in ~10–15% but typically asynchronous.
— More common in Caucasian and Asian children; rare in African American children.
— Associations: low birth weight, second-hand smoke exposure, short stature/delayed bone age, ADHD, family history.
— A 4–8-year-old boy with insidious, painless or mildly painful limp lasting weeks, often pointing to the knee, thigh, or groin (obturator referral).
— No fever, no systemic illness, no recent trauma, afebrile with normal labs — distinguishing it from septic arthritis and transient synovitis.
— Symptoms worsen with activity and improve with rest.
— Untreated or severe LCPD is a leading cause of early-onset hip osteoarthritis in adulthood, sometimes requiring THA by the 4th–5th decade.
— Outcomes depend on age at onset (younger = better), sex (girls do worse), and degree of femoral head containment.
Board pearl: Any child presenting with knee pain and a limp, exam the hip — referred pain from the obturator nerve makes LCPD (and SCFE) frequently masquerade as knee pathology, and missing this is a classic Step 3 trap. The pediatrician's job is early recognition, orthopedic referral, and activity modification, not definitive surgical decision-making in the primary care setting.
— Insidious onset, intermittent, often worse late in the day or after play.
— Pain (when present) is mild and activity-related, localizing to groin, anterior thigh, or medial knee.
— No night pain, no fevers, no weight loss — red flags for malignancy or infection if present.
— Gait described as antalgic early, Trendelenburg later (abductor weakness as femoral head deforms).
— Duration (weeks-to-months favors LCPD over septic arthritis/transient synovitis).
— Age and sex (4–8, male predominance).
— Bilateral involvement? If symmetric and simultaneous, think multiple epiphyseal dysplasia or hypothyroidism, not LCPD.
— Birth history (low birth weight), growth pattern (short stature, delayed bone age), second-hand smoke, family history of hip problems.
— Trauma history — usually absent or trivial; significant trauma should prompt other diagnoses.
— Systemic symptoms — fever, rash, other joints involved → think JIA, leukemia, septic arthritis.
— Difficulty squatting, running, climbing stairs.
— Parents may report the child "favoring one leg" or "walking funny."
Key distinction: Transient synovitis follows a viral URI by 1–2 weeks, resolves in <1–2 weeks with NSAIDs/rest, and labs are normal. LCPD persists for months, with progressive radiographic changes. Septic arthritis presents with fever, refusal to bear weight, elevated WBC/CRP/ESR — a surgical emergency.
Step 3 management: When a child presents with limp >2 weeks without infection signs, order AP and frog-leg lateral hip radiographs and refer to pediatric orthopedics — do not simply trial NSAIDs and reassess in months.
— Antalgic gait early (shortened stance phase on affected side due to pain).
— Trendelenburg gait later — pelvis drops on the contralateral side during stance on the affected leg, reflecting gluteus medius weakness from femoral head deformity and abductor lever arm shortening.
— Leg length discrepancy may develop (affected side shorter).
— Loss of internal rotation is the earliest and most reliable sign.
— Loss of abduction follows.
— Flexion and extension often preserved early.
— Compare side-to-side; pain at extremes of motion.
— Log roll test: Gentle passive internal/external rotation with the child supine and leg extended — guarding or pain suggests intra-articular hip pathology.
— FABER (Patrick) test: May reproduce groin pain.
— Thomas test: May reveal a flexion contracture.
Hemodynamic assessment is not relevant here, but vital signs matter: a febrile child with a limp gets a septic hip workup (CBC, CRP, ESR, blood cultures, hip ultrasound, possible arthrocentesis using Kocher criteria) before pursuing LCPD imaging.
Board pearl: The earliest and most sensitive exam finding in LCPD is loss of passive internal rotation of the hip in extension. Document this carefully — it both supports the diagnosis and tracks response to treatment over time.
— CBC with differential — normal in LCPD; elevated WBC suggests infection or malignancy.
— CRP and ESR — normal in LCPD; elevated in septic arthritis, osteomyelitis, JIA.
— Blood cultures if fever or systemic illness.
— Consider TSH, calcium, phosphate, alkaline phosphatase if features suggest endocrine or metabolic disease (bilateral symmetric findings, short stature out of proportion).
— Kocher criteria for septic hip (fever >38.5°C, refusal to bear weight, ESR >40, WBC >12,000) — used to triage children with acute hip pain; LCPD typically meets none.
— AP pelvis and frog-leg lateral views are standard.
— Imaging both hips is essential because 10–15% are bilateral (usually asynchronous) and the contralateral hip provides a comparison.
— Stage I (initial/ischemic): Smaller, denser femoral epiphysis; widened medial joint space; subchondral crescent (Caffey) sign — a lucent line just beneath the subchondral cortex indicating subchondral fracture, often the earliest specific finding.
— Stage II (fragmentation): Epiphysis appears fragmented with lucent and sclerotic areas.
— Stage III (reossification): New bone replaces necrotic bone.
— Stage IV (remodeling/healed): Trabecular pattern restored; residual deformity (coxa magna, coxa plana) determines long-term prognosis.
Step 3 management: When labs and radiographs are normal but the limp persists and exam shows restricted internal rotation, the next best step is MRI of the hip, not repeated x-rays in 2 weeks — early diagnosis improves containment outcomes.
— Detects marrow edema, decreased perfusion, and early necrosis weeks to months before radiographic changes appear.
— Gadolinium-enhanced (perfusion) MRI identifies the extent of avascular involvement — the percentage of epiphyseal necrosis predicts prognosis and guides treatment.
— Useful to differentiate LCPD from transient synovitis (which shows joint effusion without epiphyseal signal changes), septic arthritis, and stress fractures.
— Shows decreased uptake in the femoral head during the ischemic phase, then increased uptake during reossification.
— Largely replaced by MRI but still used in some centers.
— Detects joint effusion — useful in the acute limp workup to identify candidates for arthrocentesis when septic arthritis is on the differential.
— Does not diagnose LCPD itself.
— Performed intraoperatively to dynamically assess femoral head containment within the acetabulum and guide surgical planning.
— Group A: Lateral pillar full height — excellent prognosis.
— Group B: >50% lateral pillar height maintained — good outcome, age-dependent.
— Group B/C border: Intermediate.
— Group C: <50% lateral pillar height — worst prognosis, frequent deformity.
Key distinction: Lateral pillar classification predicts outcome during active disease; Stulberg classification predicts adult arthritis risk after healing. Both are radiographic, not clinical — but both are testable concepts on boards.
Board pearl: Younger age at onset (<6 years) and Herring A or B generally have favorable outcomes with conservative management; age >8 and Herring C often warrant surgical containment.
— Maintain femoral head containment within the acetabulum during the biologically plastic phase so it remodels into a spherical, congruent joint.
— Preserve hip range of motion, particularly abduction and internal rotation.
— Minimize pain and synovitis.
— Prevent long-term deformity (coxa magna, coxa plana, coxa irregularis) and early osteoarthritis.
— Age at onset:
— <6 years — excellent remodeling potential; most managed nonoperatively.
— 6–8 years — intermediate; individualized.
— >8 years — poorer remodeling; often surgical.
— Sex: Girls have shorter remodeling time and tend to do worse than boys of the same age.
— Lateral pillar (Herring) group: A → conservative; B/C and C → consider surgery, especially if older.
— Range of motion: Loss of abduction or hinged abduction (femoral head impinging on acetabular edge) is an indication for intervention.
— Activity modification — avoid running, jumping, impact sports during active disease.
— Protected weight-bearing with crutches as needed during painful phases.
— Physical therapy focused on maintaining abduction and internal rotation.
— NSAIDs for pain and synovitis.
— Periodic radiographs every 3–4 months to monitor stage progression and containment.
— Bracing (e.g., Petrie casts, Atlanta brace) — historically used to maintain abduction; current evidence is mixed and use has declined.
Step 3 management: For a 5-year-old with early-stage LCPD, normal range of motion, and Herring A, the correct answer is typically activity restriction, NSAIDs, physical therapy, and orthopedic follow-up — not immediate surgery.
— Ibuprofen 10 mg/kg/dose every 6–8 hours PRN (max 40 mg/kg/day, not to exceed adult dosing).
— Naproxen 5–7 mg/kg every 12 hours is an alternative for longer dosing intervals.
— Indications: pain, synovitis, limp exacerbations.
— Counsel families about GI upset, taking with food, avoiding dehydration (renal risk), and avoiding aspirin in viral illness (Reye syndrome).
— Long courses warrant periodic assessment for GI symptoms and renal function.
— Systemic steroids are a cause of osteonecrosis in other contexts (e.g., SLE) and are not used to treat LCPD.
— Intra-articular steroid injections are not standard.
— Studied for prevention of femoral head collapse; not standard of care in pediatric LCPD. May appear in question stems as a distractor.
— Ensure age-appropriate intake (vitamin D 600 IU/day for ages 1–18; calcium 700–1300 mg/day depending on age). Correct deficiency if present, but supplementation does not treat LCPD specifically.
— Encourage non-impact aerobic activity (swimming, cycling) to maintain fitness and joint mobility without loading.
Board pearl: If a Step 3 stem offers systemic corticosteroids or bisphosphonates for a child with LCPD, these are wrong answers. The correct pharmacologic plan is NSAIDs plus activity modification plus PT plus orthopedic referral — pharmacotherapy is comfort care, not cure.
— Age >8 years at onset (poorer remodeling potential).
— Herring lateral pillar B/C or C.
— Loss of containment — femoral head extruding laterally from the acetabulum.
— Hinged abduction — femoral head impinging on the lateral acetabular rim during abduction.
— Persistent pain or stiffness despite nonoperative measures.
— Femoral varus derotational osteotomy (VDRO): Proximal femur cut and angled to direct the head into the acetabulum; most common containment procedure in younger children.
— Pelvic (innominate/Salter) osteotomy: Redirects the acetabulum over the head; sometimes combined with femoral osteotomy (Shelf procedures) in older children.
— Combined procedures for severe deformity.
— Valgus extension osteotomy — for hinged abduction.
— Cheilectomy — removal of impinging lateral femoral head bone.
— Hip arthrodiastasis with external fixator — selected refractory cases.
— Adductor tenotomy to improve abduction.
— Petrie casting (broomstick casts in abduction) postoperatively or for nonoperative containment in select cases.
— Not pediatric — reserved for adults with end-stage post-LCPD osteoarthritis, often in the 30s–50s.
CCS pearl: Surgical decisions belong to pediatric orthopedics. On a CCS-style case, the appropriate primary care orders are plain radiographs of both hips, CBC/CRP/ESR if infection is on the differential, MRI if x-rays are unrevealing but suspicion remains, urgent pediatric orthopedic consultation, NSAIDs, activity restriction, and crutches — then close follow-up.
— Sickle cell disease: Femoral head osteonecrosis is common but is not LCPD — it is sickle-related AVN. Bilateral, often older children/adolescents, with characteristic crisis history. Treatment differs (hydration, transfusion strategies, hydroxyurea, orthopedic surgery).
— Hemoglobinopathies, thalassemia: Can cause femoral head AVN through marrow expansion and vascular compromise.
— Leukemia and lymphoma: Can present with bone pain and limp; CBC abnormalities and constitutional symptoms differentiate.
— Strongly suggests multiple epiphyseal dysplasia (MED), spondyloepiphyseal dysplasia (SED), or hypothyroidism rather than LCPD.
— Order skeletal survey, TSH, and consider genetics referral.
— Adjust NSAID use — avoid in significant renal impairment; use acetaminophen instead.
— Hepatic disease — acetaminophen dosing must be limited (max 75 mg/kg/day or 4 g/day, lower with hepatic disease).
— Increases mechanical load on the femoral head and complicates conservative management; also raises suspicion for SCFE in older children.
Key distinction: Bilateral symmetric femoral head changes in a short child = epiphyseal dysplasia or hypothyroidism workup. Unilateral or asynchronous bilateral changes in a 4–8-year-old boy = LCPD.
— LCPD is uncommon in this age range.
— Consider toddler's fracture (nondisplaced spiral tibia fracture), transient synovitis, septic arthritis/osteomyelitis, child abuse, developmental dysplasia of the hip (DDH) missed earlier, or discitis.
— Workup: AP pelvis and bilateral lower extremity radiographs, labs to exclude infection.
— Peak LCPD window.
— Differential: transient synovitis (post-viral, self-limited), JIA, septic arthritis, osteomyelitis, leukemia, Köhler disease (navicular AVN, foot not hip).
— SCFE becomes the dominant concern, especially in obese or rapidly growing adolescents.
— LCPD in this age group has a worse prognosis due to less remodeling potential and often requires surgical containment.
— SCFE, avulsion fractures of the pelvis (from athletic activity), labral tears, femoroacetabular impingement.
— Now adults — manage secondary osteoarthritis with weight management, PT, NSAIDs, intra-articular options, eventually THA.
— Girls develop LCPD less commonly but tend to have worse outcomes due to shorter remodeling time (earlier skeletal maturity).
— More likely to be considered for earlier surgical containment.
— Activity restriction during active disease is non-negotiable. Counsel families about return-to-play timelines (often 1–2 years).
Step 3 management: In an obese 12-year-old with hip/knee pain and limp, the next test is frog-leg lateral hip radiograph to evaluate for SCFE — and non–weight-bearing crutches until imaging is obtained to prevent slip progression.
— Synovitis flares with pain, gait changes, and ROM loss during the fragmentation phase.
— Hinged abduction — femoral head deforms into a non-spherical shape that catches on the lateral acetabulum during abduction, causing pain and limiting motion.
— Subluxation of the femoral head laterally during the plastic phase.
— Coxa magna — enlarged femoral head.
— Coxa plana — flattened femoral head.
— Coxa irregularis — aspherical, incongruent head.
— Coxa breva / shortened femoral neck — short neck with greater trochanter overgrowth.
— Greater trochanteric overgrowth with relative shortening of the neck → abductor lever arm dysfunction → persistent Trendelenburg gait.
— Leg length discrepancy (typically affected side shorter by 1–3 cm).
— Limited hip range of motion, particularly abduction and internal rotation.
— Persistent limp and reduced athletic capacity.
— Premature hip osteoarthritis — single biggest long-term complication; risk correlates strongly with Stulberg classification at skeletal maturity.
— Stulberg I/II (spherical, congruent) → minimal OA risk.
— Stulberg III/IV (aspherical, congruent) → moderate OA risk by middle age.
— Stulberg V (aspherical, incongruent) → high risk of early disabling OA.
— Total hip arthroplasty often required in the 4th to 6th decade.
— Osteotomy nonunion, hardware failure, growth plate injury, leg length issues, AVN recurrence, infection.
Board pearl: The single best predictor of adult outcome after LCPD is the Stulberg classification at skeletal maturity, which reflects femoral head sphericity and joint congruency — these in turn depend on age at onset, containment achieved, and lateral pillar status.
— All children with radiographic findings consistent with LCPD.
— Persistent limp >2–4 weeks even with negative radiographs (consider MRI before referral).
— Bilateral hip involvement.
— Loss of abduction or hinged abduction on exam.
— Fever + refusal to bear weight → emergency department for septic arthritis workup (CBC, CRP, ESR, blood cultures, hip ultrasound, arthrocentesis if effusion present).
— Acute, severe pain with sudden onset → SCFE in an adolescent; toxic-appearing child; trauma.
— Neurologic findings (back pain, weakness, bowel/bladder changes) → discitis, spinal mass.
— Systemic symptoms (weight loss, night sweats, pallor, petechiae) → leukemia workup.
— Rarely needed.
— Indicated for surgical containment procedures, perioperative pain management, postoperative casting (Petrie casts) education, or significant complications.
— Pediatric orthopedic surgery — primary specialty.
— Physical therapy — maintenance of ROM and strengthening.
— Pediatrics/primary care — coordination, growth/nutrition monitoring, school accommodations.
— Pain management/child life for prolonged casting/postoperative recovery.
— Social work for activity restriction impact on family, school, and athletic participation.
— Rheumatology if JIA is on the differential.
CCS pearl: A 5-year-old with a 3-week painless limp, normal vitals, restricted internal rotation, and a normal CBC/CRP/ESR: order AP and frog-leg lateral pelvis radiographs, consult pediatric orthopedics as outpatient within 1–2 weeks, prescribe ibuprofen PRN, and restrict from impact activities — no ED visit, no admission.
— Most common cause of acute hip pain in children 3–10 years.
— Post-viral, brief (resolves in 1–2 weeks), mild fever or afebrile, mildly elevated inflammatory markers.
— Ultrasound shows joint effusion. Treat with rest, NSAIDs, observation; resolution is the diagnostic clincher.
— Fever, refusal to bear weight, severely restricted painful ROM, elevated WBC, CRP, ESR.
— Kocher criteria stratify risk.
— Surgical emergency — hip arthrotomy and IV antibiotics.
— Fever, localized bone tenderness, elevated inflammatory markers; MRI is diagnostic.
— Older child (10–16), often obese, hip/knee pain, external rotation of the hip with passive flexion (Drehmann sign).
— Frog-leg lateral radiograph is key — slip of epiphysis off the metaphysis.
— Non–weight-bearing immediately, urgent orthopedic surgical fixation.
— Identified in infancy via Barlow/Ortolani; missed cases present with painless limp and limb length discrepancy in toddlers.
— Adolescent athletes, female triad considerations.
— Mechanical symptoms, older children/adolescents.
— Night pain dramatically relieved by NSAIDs; CT reveals nidus.
Key distinction: Transient synovitis = days to 1–2 weeks, post-viral, self-limited. LCPD = weeks to months, insidious, with progressive radiographic changes. Septic arthritis = febrile, toxic, refuses to bear weight — emergency.
— Morning stiffness, multiple joints, prolonged duration, often with elevated inflammatory markers; uveitis screening required in oligoarticular forms.
— Hip involvement is uncommon as initial presentation but possible.
— Bone pain, limp, fatigue, pallor, bruising, lymphadenopathy, hepatosplenomegaly.
— CBC may show cytopenias, blasts, or atypical cells; LDH and uric acid elevated.
— Peripheral smear and bone marrow biopsy are diagnostic.
— Always order a CBC with differential in a child with persistent unexplained bone pain or limp.
— Constitutional symptoms, palpable mass, characteristic radiographic findings (onion-skin periosteal reaction in Ewing, sunburst in osteosarcoma).
— Vaso-occlusive crises, dactylitis in younger children, AVN in older; family/personal hematologic history.
— Recurrent hemarthroses; bleeding history.
— GI symptoms, growth failure, elevated inflammatory markers.
— Diagnosis of exclusion; inconsistent exam; consider after thorough workup.
— Patterned injuries, history-exam mismatch, delayed presentation → mandatory reporting if abuse is suspected.
— Large joint (usually knee) effusion, tick exposure, serology.
— Bilateral symmetric femoral epiphyseal changes, short stature, delayed bone age — check TSH.
Board pearl: A child with bone pain, limp, and any cytopenia or systemic symptom should have a CBC with peripheral smear and inflammatory markers before being labeled with LCPD — missing pediatric leukemia is a high-stakes error.
— NSAIDs PRN for synovitis flares and activity-related pain.
— Acetaminophen as alternative.
— Avoid long uninterrupted NSAID courses without periodic reassessment.
— Ensure age-appropriate vitamin D (600 IU/day) and calcium intake.
— Avoid high-impact loading (running, jumping, contact sports) during active disease stages (Waldenström I–III, typically 1.5–3 years).
— Encourage low-impact activity — swimming, cycling — to maintain fitness, cardiovascular health, and weight.
— Gradual return to impact activity once reossification is well established and orthopedic surgeon clears.
— Maintain healthy BMI to reduce mechanical load on the hip; pediatric obesity counseling per AAP guidelines.
— Counsel on skin care, hygiene, and emergency signs (numbness, color change, severe pain).
— 504 plan for elevator access, modified PE, extended time between classes, seating accommodations.
— Keep on standard schedule; corticosteroids are not used, so live vaccine restrictions don't apply.
— Counsel families that adult hip surveillance is appropriate, especially with Stulberg III–V outcomes — periodic adult orthopedic follow-up to monitor for early OA.
Step 3 management: At discharge from active management, document the Stulberg class, residual ROM, leg length, and provide written guidance for family and PCP about long-term OA risk and red-flag symptoms (worsening pain, decreased ROM) prompting re-referral.
— During active disease, AP pelvis and frog-leg lateral radiographs every 3–4 months to track Waldenström stage and containment.
— More frequent imaging if clinical changes (worsening pain, ROM loss).
— At each visit: document hip abduction and internal rotation in degrees, gait, leg length, and pain level.
— Orthopedic follow-up every 3–4 months during active phases.
— Primary care visits at usual well-child intervals plus interim issues.
— After healing, annual orthopedic check until skeletal maturity (Stulberg classification).
— Goals: maintain abduction and internal rotation, prevent contractures, strengthen abductors.
— Home exercise program; periodic re-evaluation.
— Disease course is long (2–4 years) but generally favorable in younger children.
— Activity restriction is the hardest part for active kids — emphasize allowed activities, not just prohibited ones.
— Set realistic expectations: most children do well, but residual ROM limitations and adult OA risk exist.
— Address psychosocial impact — frustration, limited sports participation, identity issues for athletic children.
— Sudden worsening of pain.
— New refusal to bear weight.
— Fever, systemic illness.
— New leg length discrepancy or gait change.
— Awareness of early-onset hip OA risk.
— Maintain healthy weight, low-impact fitness, periodic hip ROM and pain self-assessment.
— Resume orthopedic care if symptoms develop.
CCS pearl: On a CCS case, "schedule follow-up in 3 months with repeat AP and frog-leg lateral hip radiographs" is the appropriate periodic order set — not weekly visits, not annual visits.
— Containment osteotomies are elective, complex procedures with significant risks (anesthesia, leg length issues, hardware complications, growth plate injury).
— Both parents/guardians should ideally participate in consent; for adolescents, assent is required and the child's perspective should be documented.
— Discuss alternatives (continued nonoperative management, bracing) and the uncertainty of long-term outcomes; document discussion in chart.
— A child presenting with limp, especially multiple injuries, patterned bruising, history-exam mismatch, or delayed presentation, requires evaluation for non-accidental trauma.
— Report to Child Protective Services when abuse is suspected — this is a legal mandate, not a discretionary choice.
— Skeletal survey in children <2 years if abuse is suspected.
— Children with LCPD often see multiple providers (PCP, orthopedics, PT, school). Care fragmentation can result in missed follow-up and undetected progression. Establish a medical home and shared care plans.
— At each transition (specialist to PCP, pediatric to adult care), provide a written summary of imaging history, Stulberg class, residual deficits, and surveillance plan.
— Children may qualify for 504 plans under the Rehabilitation Act for activity restrictions, mobility aids, and modified PE.
— Advocate proactively; document medical necessity.
— Access to pediatric orthopedic subspecialty care varies geographically and by insurance status. Identify barriers early; engage social work.
— Genuine safety issue — re-injury or progression can occur with noncompliance. Use motivational interviewing, family-centered goal setting, and creative alternative activities.
Board pearl: A child with a chronic limp who is lost to orthopedic follow-up because of insurance changes or family moves represents a patient safety failure. Document warm handoffs and ensure receipt of records by the new provider.
— Young children, mild disease → activity restriction, NSAIDs, PT, observation.
— Older children (>8) or Herring C → containment surgery (femoral or pelvic osteotomy).
— Septic arthritis (fever, refusal to bear weight, elevated inflammatory markers).
— SCFE (older/obese child, hip/knee pain, externally rotated hip).
— Leukemia (bone pain + cytopenias/constitutional symptoms).
— Hypothyroidism (bilateral symmetric epiphyseal changes).
Key distinction: LCPD vs SCFE — different ages (4–8 vs 10–16), different risk profile (small thin boys vs obese adolescents), different radiograph findings (epiphyseal fragmentation vs slipped metaphysis on frog-leg view), and different management urgency (orthopedic referral vs immediate non–weight-bearing and surgical fixation).
— 6-year-old boy, 6-week painless limp, normal vitals, restricted internal rotation, knee pain on history but normal knee exam, normal labs. Best next test: AP and frog-leg lateral pelvis radiographs. Answer: LCPD.
— Same scenario but radiographs are normal. Next step: MRI of the hip. Distractor: repeat x-rays in 6 weeks (wrong — early diagnosis matters for containment).
— 5-year-old with fever 39°C, refuses to bear weight, ESR 60, WBC 14,000. Answer: septic arthritis, urgent arthrocentesis and IV antibiotics — not LCPD.
— 13-year-old obese boy with knee pain and a limp; hip externally rotates with passive flexion. Answer: SCFE; non–weight-bearing and urgent orthopedic surgery.
— 5-year-old with hip pain 5 days after URI, low-grade fever, mildly elevated CRP, brief course, ultrasound effusion. Answer: transient synovitis; supportive care.
— 7-year-old short child with bilateral symmetric femoral epiphyseal changes. Best next test: TSH and skeletal survey for multiple epiphyseal dysplasia or hypothyroidism.
— Limp plus pallor, fatigue, bruising; CBC shows pancytopenia. Answer: ALL workup with peripheral smear and bone marrow, not LCPD imaging.
— Adult with prior LCPD now has early hip OA. Answer: weight management, NSAIDs, PT, eventual THA; correlates with Stulberg class V.
— Young child with Herring A, normal ROM. Answer: activity modification, NSAIDs, PT, orthopedic follow-up — not surgery.
Step 3 management: When a stem asks "next best step," distinguish diagnostic (imaging/labs) from therapeutic (NSAIDs, restriction, referral, surgery) — the question wording tells you which axis to answer on.
Legg-Calvé-Perthes disease is idiopathic avascular necrosis of the femoral capital epiphysis in a 4–8-year-old (classically a boy) presenting with an insidious painless limp and restricted hip internal rotation/abduction, diagnosed with AP and frog-leg lateral pelvic radiographs (MRI if x-rays are negative), managed with activity restriction, NSAIDs, physical therapy, and pediatric orthopedic co-management — with surgical containment reserved for older children or Herring lateral pillar B/C–C disease — and followed long-term for residual deformity and early adult hip osteoarthritis.
Board pearl: When a young child's "knee pain" persists with a limp and a normal knee exam — always image the hip.