The J-sign is when the kneecap subluxes laterally each time the knee moves into terminal extension.


Video demonstrating the J-sign



Q-angle and J-sign: Indicative of Maltracking Subgroups in Patellofemoral Pain. Sheehan FT, Derasari A, Fine KM, Brindle TJ and Katharine E. Alter KE. Clin Orthop Relat Res. 2010 Jan; 468(1): 266–275.

Clinical Accuracy of J-Sign Measurement Compared to Magnetic Resonance Imaging. Beckert MW, Albright JC, Zavala J, Chang J and Albright JP. Iowa Orthop J. 2016; 36: 94–97.

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