• Clinical science

Legg-Calvé-Perthes disease


Legg-Calvé-Perthes disease (LCPD, or Perthes disease) refers to an idiopathic, avascular necrosis of the femoral head. It may occur unilaterally or bilaterally and typically manifests between the ages of four and ten (the younger the patient at the time of diagnosis, the better the prognosis). Children experience hip pain on weight bearing, which often projects to the ipsilateral knee and causes an antalgic gait. Early stages are only detectable on MRI but progress of the disease can be tracked and graded using conventional x-ray. Surgery is performed if x-ray reveals signs that indicate an unfavorable prognosis. The aim of surgical intervention is to cover the femoral head as completely as possible with the hip socket, thus retaining its anatomical position. In mild forms of the disease, reduced weight-bearing and physical therapy are indicated.


  • Sex: > (4:1)
  • Peak incidence: 4–10 years
  • Incidence (in children < 15 years): 0.4–29/100,000


Epidemiological data refers to the US, unless otherwise specified.


  • Unknown although there are a number of hypotheses.


Lateral pillar classification

This classification possesses the highest clinical relevance because it correlates best with long-term outcome. The crucial criterion in this classification is the height of the lateral third (“lateral pillar”) of the femoral head.

Modified (Herring) Lateral pillar classification
Group A Height of the lateral pillar is 100% (no involvement)
Group B Height of the lateral pillar is > 50%
Group C Height of the lateral pillar is < 50%



Avascular necrosis of the femoral head is due to a mismatch between the rapid growth of the femoral epiphyses and the slower development of adequate blood supply to the area


Clinical features

  • Antalgic gait (on weight-bearing leg)
  • Pain in the hip or the upper leg, sometimes projecting to the knee
    • Insidious onset; , pain may fluctuate depending on physical activity
    • Often exacerbated by internal rotation
    • FABER (Flexion, ABduction, and External Rotation) test elicits pain.
    • Groin tender on palpation
  • Restricted range of movement is always present, especially regarding internal rotation and abduction.
  • Hinge abduction : refers to the lateral femoral head bumping into the ventrolateral acetabulum when the leg is abducted, possibly involving pain, a palpable clunk, and restriction in the range of movement.
  • Contralateral involvement in ∼ 15% of cases

If children complain of pain in the knee(s), Legg-Calvé-Perthes disease should be considered!



Initial imaging

  • X-ray (anterior-posterior and frog leg positions ;)
    • Frequently unremarkable during the first 3–6 months!
    • Diagnostic criteria
      • Radiographic classification: see lateral pillar classification above
      • “Head-at-risk” signs; → prognostically unfavorable radiographic signs such as increased lucency of the femoral head
      • Joint space widening
  • MRI: Indicated in case of unremarkable initial imaging (but persisting clinical suspicion)


Differential diagnoses

Differential diagnosis of pediatric hip pain

Disease Pathophysiology Clinical features Diagnostic findings
Transient synovitis
  • 4–10 years of age
  • Sex: > (2:1)
  • URI in recent weeks
  • Afebrile
  • Transient hip pain
  • Laboratory: normal
  • Imaging
    • Normal x-ray
    • Effusion on ultrasound that should improve over the course of several days (whereas it remains in LCPD)
Septic arthritis
  • Infection either by hematogenous spread of bacteria or direct contamination
  • Any age
  • Acute onset of pain and fever.
  • Fever > 38.5° C
  • Child may refuse to bear weight

Slipped capital femoral epiphysis

  • 10–16 years of age
  • Acute on chronic dull pain with antalgic gait
  • Afebrile
  • Vague hip and knee pain
  • Laboratory: normal
  • Imaging: x-ray shows displacement of the femoral head
  • Mismatch between the rapid growth of the femoral epiphyses and the slower development of adequate blood supply to the area
  • 4–10 years of age
  • Insidious onset, pain may fluctuate with activity
  • Afebrile
  • Vague hip and knee pain
  • Laboratory: normal
  • Imaging: x-ray may be unremarkable in early stages and as the disease progresses increased lucency of the femoral head may be seen
Developmental dysplasia of the hip
  • Laboratory: normal
  • Imaging: Ultrasound before 4 months and x-ray after 4 months are diagnostic

Transient synovitis (also known as toxic synovitis)

  • Epidemiology
    • Common cause of acute hip pain among children
    • Peak incidence: 4–10 years of age
    • Sex: > (2:1)
  • Pathophysiology
  • Clinical features
    • Unilateral and transient hip or groin pain
    • Recent upper respiratory tract infection in up to 50% of the patients
  • Diagnosis
    • Laboratory: mostly normal (but some cases present with mild leukocytosis and ESR elevation)
    • Imaging
      • Normal x-ray
      • Effusion on ultrasound that should improve over the course of several days
  • Treatment: conservative (i.e., NSAIDs)


The differential diagnoses listed here are not exhaustive.


  • Conservative treatment: limited weight bearing, physical therapy
    • Young children (< 6 years of age)
    • Lateral pillar A classification
    • Femoral head mostly undamaged
    • Consider casting and bracing before surgery if femoral head deformity develops or range of motion worsens
  • Surgery: femoral osteotomy
    • Older children (> 8 years of age)
    • Lateral pillar B/C classification
    • Extensive damage to the femoral head



We list the most important complications. The selection is not exhaustive.


  • Age at onset is the most important prognostic factor: the younger the patient, the better the prognosis!
  • Girls with LCPD have a less favorable prognosis than boys.