Ferlic PW, Runer A, Seeber C, et al. - This study was undertaken to investigate the reliability of nine commonly used quantitative parameters of the trochlear morphology in computed tomography (CT) and b) to examine for variations in the reliability with regard to patient sub-groups (PFI vs. non-PFI). Researchers conducted a retrospective analysis of lower limb CT scans between August 1996 and February 2013. In this study, four investigators conducted the measurements independently and intraclass correlation coefficients were estimated for the entire study group as well as for the PFI and non-PFI group separately. The study enrolled a total of 66 cases (36 PFI). Considerably lower reliability of angular parameters such as the commonly used sulcus angle compared to linear measurements must be taken into account, when interpreting quantitative parameters defining the trochlear morphology. It was shown that in cases of patellofemoral instability radiologic measurements are less reliable than in individuals without instability.