Age changes everything
Read across, then answer.
The hip pathologies of childhood are stacked by age: developmental dysplasia in the infant, transient synovitis and septic arthritis in the small child, Perthes in the school-aged, slipped upper femoral epiphysis in the adolescent.
18 months
Septic arthritis and osteomyelitis, the toddler's fracture, and non-accidental injury.
Differential
What changes
A toddler who refuses to weight-bear with a fever is septic arthritis until proven otherwise. Examine every joint, the spine and the feet. Does the story fit the child's mobility?
4 years
Transient synovitis versus septic arthritis: the same hip, opposite urgency.
Differential
What changes
The features that push toward septic arthritis are fever, inability to weight-bear, a raised inflammatory marker and a raised white count. Ultrasound shows the effusion; only aspiration tells you what is in it. Persistent or night pain with pallor or bruising is a blood count question.
9 years
Perthes disease and the malignancy that presents as a limp.
Differential
What changes
A limp of weeks with limited internal rotation and abduction of the hip needs an X-ray of both hips, including a frog-leg lateral. Night pain and systemic features are red flags.
13 years
Slipped upper femoral epiphysis, which presents as knee pain as often as hip pain.
Differential
What changes
Any adolescent with knee pain gets the hip examined. A slipped epiphysis is non-weight-bearing and an urgent orthopedic referral; a missed slip is a lifelong hip.
A 13-year-old with three weeks of knee pain and a limp; the knee examination is normal. What next?
The adult frame, for contrast