Perthes Disease

What is Perthes disease?

Perthes disease — also called Legg-Calvé-Perthes — is a condition in which the blood supply to the head of the thigh bone (the femoral head) is temporarily disrupted in childhood. The bone softens, can collapse partially, and then gradually reforms over months to years.

It typically affects children between 4 and 10 years old, more commonly boys. The cause isn't fully understood and there's usually no specific trigger. One hip is usually affected, though both can be involved.

Outcomes vary considerably depending on age at onset, severity and how the hip remodels. The younger the child at diagnosis, the more potential for the hip to reshape successfully — older children tend to have a more challenging journey.

What does it feel like?

The presentation is often gradual. Common features include:

• A persistent limp, sometimes for weeks or months

• Pain in the hip, groin or referred to the thigh or knee

• Restricted hip movement, particularly internal rotation and abduction

• Stiffness after rest

• Fluctuating symptoms — better some days than others

Pain is often less prominent than the limp, which can lead to delays in diagnosis. Children sometimes adapt and continue to play with a noticeable but not disabling limp.

How is it diagnosed?

Examination establishes restricted hip movement and helps localise the problem. Imaging is essential to confirm the diagnosis and stage the disease.

X-rays are the standard initial investigation and may show the typical changes of Perthes. MRI is increasingly used early in the process — it can show changes before they appear on X-rays and helps with staging and prognosis.

The full picture comes together over time, since Perthes evolves through phases. Repeat imaging is part of the management.

What are the treatment options?

Treatment varies enormously and depends on age, severity, the stage of the disease and how the hip is behaving. Younger children with milder involvement often do well with simple measures — physiotherapy, activity modification, and time. Older children or those with more extensive involvement may need surgical intervention to optimise how the hip remodels.

There's no one-size-fits-all answer in Perthes. The decisions are individual and depend on factors specific to your child. Nev will work through this with you at your consultation, so any plan reflects what's right for your child's particular situation.

When should you get it checked?

Seek a specialist assessment if:

• Your child has a persistent limp lasting more than a few weeks

• There's hip, thigh or knee pain that isn't behaving like a normal niggle

• You've been told there's a possibility of Perthes and want a clear plan

• Symptoms are fluctuating and you'd like a structured assessment

• You want a proper understanding of what's happening and what to expect

Perthes is a long journey for most families, but a well-considered plan from the outset makes a substantial difference. An accurate assessment is the cornerstone of getting it right.