Line of Klein

Last revised by Andrea Molinari on 15 Feb 2024

The line of Klein describes an arbitrary line drawn along the superior edge of the femoral neck, which is useful in detecting early slipped upper femoral epiphysis in adolescents.

The line should normally intersect the lateral aspect of the superior femoral epiphysis. Failure of intersection can indicate slipped upper femoral epiphysis​, and this radiographic finding is termed Trethowan sign 1. In very subtle cases, asymmetry between the lines of Klein may be the only way of determining a slipped upper femoral epiphysis.

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