Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services after a major injury if the leg appears deformed, or if the foot becomes cold, pale, numb, or weak.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Contact the child's orthopaedic team sooner than planned if known symptoms are worsening, prescribed exercises can no longer be completed, a cast or brace is causing skin problems, or pain is no longer controlled by the agreed plan.
Seek urgent same-day care if a child:
Suddenly cannot stand or put weight on the leg
Has severe or rapidly worsening hip pain
Has hip pain with fever or appears seriously unwell
Develops a hot, swollen, or red joint
These features are not typical of uncomplicated Legg-Calve-Perthes and may indicate an infection, fracture, or another urgent hip problem.
And for anyone, someone who:
is getting rapidly more short of breath, or has gained several pounds in a few days with swelling
3
Does any of this apply?
Book an appointment
Arrange a routine medical appointment if your child has a limp that persists or keeps returning, unexplained hip or knee pain, reduced hip movement, or difficulty keeping up with usual activities.
A limp without pain still deserves assessment.
Every sign above is quoted from the sofidex article on Legg-calve-perthes disease. If you are not sure, err upward — it is always reasonable to be checked.