| What We Treat
Perthes Disease
A limping child with hip or knee pain needs assessment. Perthes affects the blood supply to the hip and the outcome depends on early recognition.
Overview
What It Is
Perthes disease is a temporary loss of blood supply to the head of the femur in children, typically between four and eight years old. The bone softens, may deform, and then gradually reossifies over one to three years. The long-term outcome depends heavily on preserving hip shape and movement during that period, which is where physiotherapy contributes.
Tap a structure, or use the buttons, to see what may be involved.
Interrupted Blood Supply
The head of the femur temporarily loses its blood supply, softens, and reforms over one to three years.
Symptoms
How It Tends to Feel
These are the features that point towards this diagnosis rather than another:
Limp
Often painless initially, and the most common presenting feature.
Knee or Thigh Pain
Hip problems in children very frequently present as knee pain.
Reduced Hip Movement
Particularly internal rotation and abduction — a key examination finding.
Intermittent Symptoms
Coming and going over weeks, which delays presentation.
Worse After Activity
Settling with rest.
Leg Length Difference
In more advanced cases.
Causes & Risk Factors
What Drives It
The usual contributors, in rough order of how often they turn out to matter:
Interrupted Blood Supply
The underlying mechanism, though the cause is not established.
Age and Sex
Most common in boys aged four to eight.
Bilateral in a Minority
Where both hips are affected, other diagnoses are considered.
Associations
Lower birth weight, passive smoke exposure and higher activity levels are reported.
How We Can Help You
Treatment & Management
Treatment is built around what the assessment finds, but generally follows this shape:
When to Seek Help
Red Flags — Don’t Ignore These
Most presentations are straightforward. These features are the exceptions, and warrant prompt assessment:
⚠ Seek Medical Advice If You Notice
- A child who refuses to weight bear at all — urgent assessment required
- Fever with hip pain — septic arthritis must be excluded urgently
- Rapid loss of hip movement
- Night pain, weight loss or systemic illness
If any of these apply, contact your GP or seek urgent medical care rather than waiting for a physiotherapy appointment.
Common Questions
Frequently Asked Questions
Why does my child complain of knee pain?
Hip pathology in children very commonly refers to the knee. Any child with knee pain needs their hip examined, and this is a frequent cause of delayed diagnosis.
How long does it last?
The process typically runs over eighteen months to three years, passing through distinct phases before the bone reforms.
What is the long-term outlook?
Generally good in younger children with well-maintained hip shape and movement. Older age at onset and greater deformity carry more risk of later arthritis.
Not Sure If This Is What You Have?
An assessment will tell you what is actually going on and what to do about it. I see everyone myself, and you will leave with a plan rather than a leaflet.
Book Your Initial AssessmentThis page is for general information only and isn’t a substitute for individual medical advice. If you’re experiencing any of the warning signs above, contact your GP or seek emergency medical care as appropriate.