The Kocher criteria can help you rule out a septic hip. Transient Synovitis is a much better diagnosis. It used to be called Toxic Synovitis, but that name was too scary so it got changed.
Lyrics
In a kid with hip pain
I’ve got to explain
The Kocher criteria
And using your brain
Cannot bear weight
A fever complaint
White count 12K
ESR 40 today
I’ve they’ve got all four
The hips septic for sure
But if they have none
Then show them the door
Note: CRP of >2.5 can replace ESR>40, but it was more fun to have him sing ESR…