Idiopathic avascular necrosis of the proximal femoral epiphysis in children aged 4-8.
Also known as: Legg-Calve-Perthes, Perthes disease, LCPD, coxa plana
Overview
Idiopathic osteonecrosis of the femoral head occurring in growing children, characterized by self-limited interruption of vascular supply to the capital femoral epiphysis followed by revascularization, resorption, reossification, and remodeling.
Epidemiology
Incidence 1 in 1,200 to 1 in 12,000 children. Peak age 4-8 years (range 2-12). Male-to-female ratio 4-5:1. Bilateral involvement in 10-15 percent (usually asynchronous).
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Question 1MusculoskeletalEasy
A 7-year-old boy has a 3-week history of a painful limp. Radiograph shows flattening and sclerosis of the left femoral head epiphysis with preserved joint space. WBC and ESR are normal. Which of the following is the most likely diagnosis?
ATransient synovitis of the hip
BOsteoid osteoma of the proximal femur
CSlipped capital femoral epiphysis
DLegg-Calve-Perthes disease
Reveal answer & full explanation
Correct answer: D — Legg-Calve-Perthes disease
ATransient synovitis of the hip
BOsteoid osteoma of the proximal femur
CSlipped capital femoral epiphysis
DLegg-Calve-Perthes disease✓
Why Legg-Calve-Perthes disease is correct
Legg-Calve-Perthes disease is idiopathic avascular necrosis of the femoral head in children (ages 4–10, males 4:1).
Radiographs show sclerosis, fragmentation, and flattening of the femoral head epiphysis with preserved joint space.
Normal WBC and ESR argue against an infectious cause.
Treatment: activity restriction, physiotherapy, and containment (orthosis or surgery for severe cases).
Prognosis is better in children younger than 8.
Why the others are wrong
Transient synovitis of the hip — A self-limited postviral hip irritability that resolves within days to about 2 weeks and leaves radiographs normal, not a 3-week limp with epiphyseal flattening and sclerosis.
Osteoid osteoma of the proximal femur — Causes night pain dramatically relieved by NSAIDs and shows a small lucent nidus with surrounding cortical sclerosis, not flattening of the femoral head epiphysis.
Slipped capital femoral epiphysis — Typically affects obese adolescents (ages 10–16) and shows posteroinferior slippage of the epiphysis off the metaphysis, not the femoral-head sclerosis and flattening seen here in a 7-year-old.
Question 2MusculoskeletalMedium
A 7-year-old boy has insidious hip pain, a painless limp, and limited abduction and internal rotation. Radiograph shows flattening of the femoral head. Which of the following is the most likely diagnosis?
ATransient synovitis of the hip
BSlipped capital femoral epiphysis
CLegg-Calve-Perthes disease
DDevelopmental hip dysplasia
Reveal answer & full explanation
Correct answer: C — Legg-Calve-Perthes disease
ATransient synovitis of the hip
BSlipped capital femoral epiphysis
CLegg-Calve-Perthes disease✓
DDevelopmental hip dysplasia
Why Legg-Calve-Perthes disease is correct
Legg-Calve-Perthes is idiopathic avascular necrosis of the femoral head, peaking in boys aged 4-8 years.
It presents with insidious painless limp, groin or referred knee pain, and restricted abduction and internal rotation.
Radiographs progress from increased femoral-head density to fragmentation and the flattening seen here.
Why the others are wrong
Slipped capital femoral epiphysis — SCFE affects obese adolescents (10-16 years) and shows posteroinferior epiphyseal slip, not femoral-head flattening in a 7-year-old (age/mechanism mismatch).
Transient synovitis of the hip — Post-viral transient synovitis causes an acute limp but has a normal radiograph and resolves in days, unlike the structural head change here (self-limited mimic).
Developmental hip dysplasia — Late-presenting dysplasia also gives a painless limp with limited abduction, but it predominates in girls and shows a shallow dysplastic acetabulum with a subluxed head rather than a flattened femoral head (shared-presentation mimic).
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Disruption of blood supply to the femoral head produces avascular necrosis. Disease evolves through four radiographic stages (Waldenström): initial (sclerosis and apparent enlargement), fragmentation (subchondral fracture and lucency), reossification (new bone formation), and residual (remodeling). The shape achieved at skeletal maturity determines long-term hip function.
Clinical presentation
Symptoms
Insidious, painless or mildly painful limp
Hip, groin, thigh, or referred knee pain
Decreased activity tolerance
Symptoms typically persist over weeks to months without an acute event
Signs / physical exam
Antalgic and Trendelenburg gait
Decreased hip abduction and internal rotation
Mild thigh atrophy from disuse
Leg length discrepancy in advanced disease
Classic findings
Young boy aged 4-8 with a painless limp, restricted internal rotation and abduction of the hip, and characteristic crescent sign or femoral head flattening on radiographs.
Lateral pillar (Herring) classification at the fragmentation stage assesses the height of the lateral one-third of the epiphysis: A — full height preserved (best prognosis); B — at least 50 percent of original height; B/C border — exactly 50 percent or narrow lateral pillar; C — less than 50 percent of height (worst prognosis). Age at onset is the other major prognostic variable — younger children (<6 years) generally do better.
Labs
CBC, ESR, CRP normal in LCPD — distinguishes from septic arthritis and osteomyelitis
Consider hemoglobin electrophoresis if sickle cell osteonecrosis is in the differential
Imaging
AP and frog-leg lateral pelvic radiographs
Early findings: increased epiphyseal density, joint space widening, crescent sign (subchondral fracture)
Later findings: epiphyseal fragmentation, flattening, lateral extrusion of the femoral head
MRI for early disease before radiographic changes appear
Diagnostic algorithm
Lateral Pillar (Herring)
Lateral 1/3 Epiphysis Height
Prognosis
A
Full original height
Excellent — observation
B
≥50% of original height
Good in <8 yr; variable in older
B/C border
Exactly 50% or narrow
Intermediate — surgery often considered
C
<50% of original height
Poor — high risk for deformity
Lateral pillar (Herring) classification of Legg-Calvé-Perthes disease and prognosis.
Treatment
First-line
Activity restriction to limit hip joint loading and protect the femoral head during fragmentation
NSAIDs for pain
Physical therapy emphasizing hip range of motion (abduction and internal rotation)
Crutches or partial weight bearing for symptomatic relief
Observation alone for children <6 years with lateral pillar A or B disease
Second-line / adjunct
Containment treatment (keep the femoral head 'contained' within the acetabulum during healing) — bracing has largely fallen out of favor; surgical containment via femoral varus osteotomy or innominate (Salter) pelvic osteotomy considered for children ≥6-8 years with lateral pillar B or B/C border disease
Salvage procedures (femoral osteotomy, hip arthroscopy) for late deformity and impingement
Total hip arthroplasty in early adulthood for end-stage post-Perthes arthritis
Complications
Coxa magna and coxa plana (large, flattened femoral head)
Femoral head deformity with hinge abduction
Leg length discrepancy
Early osteoarthritis of the hip — accelerated by older age at onset and severe lateral pillar involvement
Femoroacetabular impingement
PANCE pearls
LCPD typically affects younger children (4-8) and SCFE older adolescents (10-16) — age is the most useful initial differentiator.
Knee pain in a child is hip pain until proven otherwise — examine the hip and obtain pelvic radiographs.
Age at onset and lateral pillar classification together are the strongest predictors of outcome; children diagnosed before age 6 with intact lateral pillar generally do well without surgery.
The natural history of LCPD is healing — the goal of treatment is to optimize the shape of the femoral head at skeletal maturity, not to alter the disease course.
References
POSNA — Pediatric Orthopaedic Society of North America clinical resources on Legg-Calvé-Perthes disease
AAOS — American Academy of Orthopaedic Surgeons evidence-based guidance on Perthes disease
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