Patellofemoral evaluation with radiographs and computed tomography scans in 60 knees of asymptomatic subjects

The objectives of this study were to show the results of patellofemoral joint imaging in healthy volunteers, to propose a standardization of the technique, and to test the statistical correlation and reliability of the different imaging results. Methods: In 30 healthy police academy student volunteers of both sexes, standard knee radiographs and computed tomography (CT) scans were obtained. The angles and distances were measured, and a statistical analysis was applied. The results are presented as mean +/- 2 SDs throughout. Results: The mean Laurin lateral patellofemoral angle on radiographs was 16.4 degrees +/- 8.7 degrees. The mean Insall-Salvati and Caton-Deschamps indexes were 1.09 +/- 0.24 and 0.95 +/- 0.29, respectively. The CT scan values for tilt were determined for the lateral patellofemoral angle by use of both facets (-8.1 degrees - 9.8 degrees), the Laurin lateral patellofemoral angle (8.1 degrees +/- 14.5 degrees), the condyle-patellar angle with the lateral facet (14.5 degrees +/- 14 degrees), and the patella major axis (-11.1 degrees +/- 10.6 degrees). The sulcus angle, congruence angle (Merchant angle), and condyle-lateral angle were also obtained on CT scans, with mean values of 139.7 degrees +/- 20.4 degrees, 5.15 degrees +/- 32.6 degrees, and 22.1 degrees +/- 9 degrees, respectively. The tibiofemoral rotation was assessed with the indexes for the distance between the trochlear groove and anterior tibial tuberosity and the distance between the posterior femoral dome and anterior tibial tuberosity. The values for these two indexes were 13.6 +/- 8.8 min and 17.8 +/- 9.2 mm, respectively. Some parameters showed sex differences. Conclusions: There are good statistical correlations between some of the tilt values on the radiographs and CT scans, indicating that they move together. The values on the CT scans show good reliability. The CT scans and radiographs are good tests by which to evaluate and quantify patellar alignment. Level of Evidence: Level 1, testing of previously developed diagnostic criteria.