Crossing sign (knee)

Last revised by Dr Henry Knipe on 18 May 2020

The crossing sign is seen on true lateral plain radiographs of the knee when the line of the trochlear groove crosses the anterior border of one of the condyle trochlea. It is a predictor of trochlear dysplasia. Trochlear dysplasia has been linked to recurrent patellar dislocation 1,2,4. The crossing sign is sensitive but not specific in diagnosing trochlear dysplasia, and has a sensitivity of 94% and a specificity of 56% 3,4.

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