An adolescent with hip or knee pain: the epiphysis slips posteriorly and inferiorly — the frog-leg lateral view shows it first; Klein line and the metaphyseal blanch sign on the AP catch the rest, and the other hip must be checked.
Orient first
- Obese adolescents, often during the growth spurt; bilateral in a significant proportion.
- Knee pain is a common presentation — examine and image the hip.
- Severity by the slip angle (Southwick) on the lateral view (verify grading).
Acquire the study
- AP pelvis and frog-leg lateral views of both hips (a cross-table lateral if unstable).
The manoeuvre
- AP view: Klein line along the superior femoral neck should intersect the epiphysis — if not, slipped.
- AP: widened, irregular physis; metaphyseal blanch sign (double density).
- Frog-leg lateral: posterior displacement of the epiphysis — measure the slip angle in degrees.
- Compare the other hip.
What confirms it
- Posterior or inferior epiphyseal displacement on the lateral view, or abnormal Klein line with a widened physis.
What licenses you to exclude it
- Normal AP and lateral views with symmetric physes make SCFE unlikely; early pre-slip may need MRI.
The classic misread
- Imaging only the knee in a child with knee pain.