Medical Conditions

Legg-Calve-Perthes Disease (Hip Avascular Necrosis)

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published OrthoInfo, AAP, NIH guidelines

Editorial policy

Last reviewed:

If your baby has been diagnosed with or you suspect legg-calve-perthes disease (hip avascular necrosis), here is what the evidence says.

The short answer

Legg-Calve-Perthes disease occurs when the blood supply to the ball (femoral head) of the hip joint is temporarily disrupted, causing the bone to soften and break down. It most commonly affects children between ages 2 and 12, with a peak between 4 and 8, and is about four times more common in boys. With proper treatment ranging from observation and physical therapy to bracing or surgery, most children recover well over 1-2 years as the bone gradually regrows.

Key takeaways

  • Legg-Calve-Perthes disease occurs when the blood supply to the ball (femoral head) of the hip joint is temporarily disrupted, causing the bone to soften and break down. It most commonly affects children between ages 2 and 12, with a peak between 4 and 8, and is about four times more common in boys. With proper treatment ranging from observation and physical therapy to bracing or surgery, most children recover well over 1-2 years as the bone gradually regrows.
  • Usually normal when: Your child has been diagnosed with Perthes disease and is being actively monitored by a pediatric orthopedist with regular imaging
  • Call your doctor if: Your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than Perthes disease and requires emergency evaluation
  • Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
— Fever and Your Child, American Academy of Pediatrics (AAP)

Parents everywhere have the same worry. You are doing the right thing by looking into it.

What Parents Should Know

According to OrthoInfo, AAP, NIH guidelines, legg-Calve-Perthes disease occurs when the blood supply to the ball (femoral head) of the hip joint is temporarily disrupted, causing the bone to soften and break down. It most commonly affects children between ages 2 and 12, with a peak between 4 and 8, and is about four times more common in boys. With proper treatment ranging from observation and physical therapy to bracing or surgery, most children recover well over 1-2 years as the bone gradually regrows. At 0-3 months, legg-Calve-Perthes disease does not occur at this age. Hip concerns in newborns are typically related to developmental dysplasia of the hip (DDH). If your newborn has hip instability, asymmetric thigh folds, or limited hip movement, your pediatrician will evaluate for DDH rather than Perthes disease. It is generally considered normal when your child has been diagnosed with Perthes disease and is being actively monitored by a pediatric orthopedist with regular imaging. However, you should contact your pediatrician promptly if your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than Perthes disease and requires emergency evaluation.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your child has been diagnosed with Perthes disease and is being actively monitored by a pediatric orthopedist with regular imaging
Your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than Perthes disease and requires emergency evaluation
Your child has mild involvement affecting less than half the femoral head and is maintaining good hip range of motion with physical therapy
Your child with known Perthes disease develops sudden worsening of pain or a dramatic decrease in hip range of motion, which could indicate femoral head collapse requiring urgent orthopedic assessment
Your child was diagnosed before age 6, which is associated with a more favorable long-term prognosis
Your child has a persistent limp lasting more than a few days, especially without a clear injury
Your child's pain is manageable and improves with rest, activity modification, and anti-inflammatory medication as directed by your doctor
Your child complains of recurring hip, groin, thigh, or knee pain that worsens with activity

By Age

What to expect by age

0-3 months

Legg-Calve-Perthes disease does not occur at this age. Hip concerns in newborns are typically related to developmental dysplasia of the hip (DDH). If your newborn has hip instability, asymmetric thigh folds, or limited hip movement, your pediatrician will evaluate for DDH rather than Perthes disease.

3-12 months

Perthes disease is essentially unheard of in infants under 1 year. If your baby shows signs of hip discomfort, limited hip movement, or reluctance to bear weight once standing, other conditions such as hip dysplasia, transient synovitis, or infection are far more likely and should be evaluated by your pediatrician.

1-3 years

Perthes disease can occasionally appear in this age group, though it is more common in older children. Early signs include a painless limp that comes and goes, mild hip or knee pain (referred pain to the knee is common and can be misleading), and stiffness after activity. Children diagnosed younger generally have a better prognosis because the femoral head has more time to remodel during growth. X-rays are the primary diagnostic tool, and early cases may show only subtle changes.

3-5 years

This is within the peak age range for Perthes disease. Your child may develop a painless limp, complain of hip, thigh, groin, or knee pain (especially after activity), or have reduced range of motion in the affected hip, particularly internal rotation and abduction. Diagnosis is confirmed with X-rays, and MRI may be needed to assess the extent of femoral head involvement. Treatment depends on how much of the femoral head is affected and may include activity modification, physical therapy to maintain hip motion, abduction bracing (such as a Petrie cast or Scottish Rite brace), or in more severe cases, surgical osteotomy to keep the femoral head well-contained in the hip socket.

What to Tell Your Pediatrician

  • Describe when you first noticed legg-calve-perthes disease (hip avascular necrosis) and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child has a persistent limp lasting more than a few days, especially without a clear injury.
  • Mention if your child complains of recurring hip, groin, thigh, or knee pain that worsens with activity.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Your child has been diagnosed with Perthes disease and is being actively monitored by a pediatric orthopedist with regular imaging
  • Your child has mild involvement affecting less than half the femoral head and is maintaining good hip range of motion with physical therapy
  • Your child was diagnosed before age 6, which is associated with a more favorable long-term prognosis
  • Your child's pain is manageable and improves with rest, activity modification, and anti-inflammatory medication as directed by your doctor
Mention at your next visit when...
  • Your child has a persistent limp lasting more than a few days, especially without a clear injury
  • Your child complains of recurring hip, groin, thigh, or knee pain that worsens with activity
  • You notice your child has limited ability to spread or rotate the affected hip compared to the other side
Act now when...
  • Your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than Perthes disease and requires emergency evaluation
  • Your child with known Perthes disease develops sudden worsening of pain or a dramatic decrease in hip range of motion, which could indicate femoral head collapse requiring urgent orthopedic assessment

What You Can Do at Home

  • Keep track of when you notice legg-calve-perthes disease (hip avascular necrosis) — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your child has been diagnosed with Perthes disease and is being actively monitored by a pediatric orthopedist with regular imaging — this is generally within the range of normal.
  • At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
  • While monitoring at home, seek immediate care if your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than Perthes disease and requires emergency evaluation.

Baby Hip Dysplasia (Hip Click)

Developmental dysplasia of the hip (DDH) is a condition where the hip joint does not form properly, ranging from mild looseness to complete dislocation. It occurs in about 1 in 1,000 births and is more common in firstborns, girls, breech babies, and those with a family history. When caught early, treatment with a soft brace (Pavlik harness) is highly effective.

My Baby or Toddler Is Limping

A limp in a baby or toddler always deserves medical attention, as young children cannot reliably tell you where it hurts. The most common cause in toddlers is a minor injury such as a 'toddler's fracture' (a subtle shin bone crack) or muscle strain. However, limping can also indicate infection in a joint or bone, hip problems, or other conditions that need prompt evaluation.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is legg-calve-perthes disease (hip avascular necrosis) normal?
Legg-Calve-Perthes disease occurs when the blood supply to the ball (femoral head) of the hip joint is temporarily disrupted, causing the bone to soften and break down. It most commonly affects children between ages 2 and 12, with a peak between 4 and 8, and is about four times more common in boys. With proper treatment ranging from observation and physical therapy to bracing or surgery, most children recover well over 1-2 years as the bone gradually regrows.
When should I call the doctor about legg-calve-perthes disease (hip avascular necrosis)?
Your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than Perthes disease and requires emergency evaluation Your child with known Perthes disease develops sudden worsening of pain or a dramatic decrease in hip range of motion, which could indicate femoral head collapse requiring urgent orthopedic assessment
When is legg-calve-perthes disease (hip avascular necrosis) normal?
Your child has been diagnosed with Perthes disease and is being actively monitored by a pediatric orthopedist with regular imaging Your child has mild involvement affecting less than half the femoral head and is maintaining good hip range of motion with physical therapy Your child was diagnosed before age 6, which is associated with a more favorable long-term prognosis
What causes legg-calve-perthes disease (hip avascular necrosis)?
Legg-Calve-Perthes disease occurs when the blood supply to the ball (femoral head) of the hip joint is temporarily disrupted, causing the bone to soften and break down. It most commonly affects children between ages 2 and 12, with a peak between 4 and 8, and is about four times more common in boys. With proper treatment ranging from observation and physical therapy to bracing or surgery, most children recover well over 1-2 years as the bone gradually regrows. Common explanations include: Your child has been diagnosed with Perthes disease and is being actively monitored by a pediatric orthopedist with regular imaging. Your child has mild involvement affecting less than half the femoral head and is maintaining good hip range of motion with physical therapy.
What should I mention to my pediatrician about legg-calve-perthes disease (hip avascular necrosis)?
You should mention legg-calve-perthes disease (hip avascular necrosis) at your next visit if: Your child has a persistent limp lasting more than a few days, especially without a clear injury. Your child complains of recurring hip, groin, thigh, or knee pain that worsens with activity. You notice your child has limited ability to spread or rotate the affected hip compared to the other side.
Is legg-calve-perthes disease (hip avascular necrosis) normal at 0-3 months?
Legg-Calve-Perthes disease does not occur at this age. Hip concerns in newborns are typically related to developmental dysplasia of the hip (DDH). If your newborn has hip instability, asymmetric thigh folds, or limited hip movement, your pediatrician will evaluate for DDH rather than Perthes disease.
Is legg-calve-perthes disease (hip avascular necrosis) normal at 3-12 months?
Perthes disease is essentially unheard of in infants under 1 year. If your baby shows signs of hip discomfort, limited hip movement, or reluctance to bear weight once standing, other conditions such as hip dysplasia, transient synovitis, or infection are far more likely and should be evaluated by your pediatrician.
Should I go to the ER for legg-calve-perthes disease (hip avascular necrosis)?
Seek emergency care if your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than Perthes disease and requires emergency evaluation, or if your child with known Perthes disease develops sudden worsening of pain or a dramatic decrease in hip range of motion, which could indicate femoral head collapse requiring urgent orthopedic assessment. When in doubt, call your pediatrician's after-hours line for guidance.
Does legg-calve-perthes disease (hip avascular necrosis) go away on its own?
In many cases, legg-calve-perthes disease (hip avascular necrosis) resolves on its own, especially when your child has been diagnosed with Perthes disease and is being actively monitored by a pediatric orthopedist with regular imaging. By 3-5 years, this is within the peak age range for Perthes disease. Your child may develop a painless limp, complain of hip, thigh, groin, or knee pain (especially after activity), or have reduced range of motion in the affected hip, particularly internal rotation and abduction. Diagnosis is confirmed with X-rays, and MRI may be needed to assess the extent of femoral head involvement. Treatment depends on how much of the femoral head is affected and may include activity modification, physical therapy to maintain hip motion, abduction bracing (such as a Petrie cast or Scottish Rite brace), or in more severe cases, surgical osteotomy to keep the femoral head well-contained in the hip socket.
ORTHOINFOAAPNIH

References

  1. [1]American Academy of Orthopaedic Surgeons. Perthes Disease. OrthoInfo, 2022. OrthoInfo
  2. [2]American Academy of Pediatrics. Legg-Calve-Perthes Disease. HealthyChildren.org. AAP
  3. [3]National Institutes of Health. Legg-Calve-Perthes Disease. MedlinePlus, 2023. NIH

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Legg-Calve-Perthes Disease (Hip Avascular Necrosis).

Things to mention

  • Describe when you first noticed legg-calve-perthes disease (hip avascular necrosis) and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child has a persistent limp lasting more than a few days, especially without a clear injury.
  • Mention if your child complains of recurring hip, groin, thigh, or knee pain that worsens with activity.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your child has a persistent limp lasting more than a few days, especially without a clear injury
  • Your child complains of recurring hip, groin, thigh, or knee pain that worsens with activity
  • You notice your child has limited ability to spread or rotate the affected hip compared to the other side

Urgent signs to report immediately

  • Your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than Perthes disease and requires emergency evaluation
  • Your child with known Perthes disease develops sudden worsening of pain or a dramatic decrease in hip range of motion, which could indicate femoral head collapse requiring urgent orthopedic assessment

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

Well-Baby Visit PrepMedicine Dosage CalculatorBaby Tracker

Bottom line

Most cases of legg-calve-perthes disease (hip avascular necrosis) are normal. Talk to your pediatrician if your child suddenly cannot bear weight on the leg, has severe hip pain, and has a fever, which may indicate a joint infection (septic arthritis) rather than perthes disease and requires emergency evaluation.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

Share:FacebookX

Was this page helpful?

Related Medical Concerns

Baby Hip Dysplasia (Hip Click)

Developmental dysplasia of the hip (DDH) is a condition where the hip joint does not form properly, ranging from mild looseness to complete dislocation. It occurs in about 1 in 1,000 births and is more common in firstborns, girls, breech babies, and those with a family history. When caught early, treatment with a soft brace (Pavlik harness) is highly effective.

My Baby or Toddler Is Limping

A limp in a baby or toddler always deserves medical attention, as young children cannot reliably tell you where it hurts. The most common cause in toddlers is a minor injury such as a 'toddler's fracture' (a subtle shin bone crack) or muscle strain. However, limping can also indicate infection in a joint or bone, hip problems, or other conditions that need prompt evaluation.

My Baby's Head Shape Looks Abnormal

Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.

Achondroplasia (Dwarfism) in Babies

Achondroplasia is the most common form of short-limbed dwarfism, affecting about 1 in 15,000 to 40,000 births. It is caused by a mutation in the FGFR3 gene and is usually apparent at birth with characteristic features including short limbs, a larger head, and a prominent forehead. Intelligence is normal. With monitoring for specific complications and supportive care, children with achondroplasia lead full, active, and independent lives.

Adenoid Hypertrophy and Breathing

Adenoids are lymphoid tissue located behind the nose that help fight infection in young children. When adenoids become enlarged (adenoid hypertrophy), they can block the nasal airway, causing chronic mouth breathing, snoring, nasal speech, and sleep-disordered breathing. Enlarged adenoids are most common between ages 2-7 and are a leading cause of obstructive sleep apnea in young children. Treatment ranges from watchful waiting and nasal steroids to surgical removal (adenoidectomy) if breathing or sleep is significantly affected.

Adrenoleukodystrophy (ALD) in Babies

X-linked adrenoleukodystrophy (X-ALD) is a genetic disorder affecting about 1 in 17,000 newborns, caused by mutations in the ABCD1 gene on the X chromosome. It primarily affects boys and impairs the breakdown of very long-chain fatty acids (VLCFAs), which accumulate and damage the myelin sheath in the brain and the adrenal glands. The most severe form, cerebral ALD, typically affects boys between ages 4-10 with rapid neurological decline. Newborn screening now enables early detection, and hematopoietic stem cell transplant or gene therapy performed before significant brain involvement can be life-saving.