Correlation between the Q angle and the patella position: a clinical and axial computed tomography evaluation

The purpose of this study was to evaluate the significance of the Q angle with respect to the patella position. Fifty-six knee joints of 34 patients (15 bilateral) with chronic patellofemoral pain were prospectively evaluated. All patients were examined by the same orthopaedic surgeon (R.M.B.) and the Q angle measured clinically and using long radiographs. Additionally, axial computed tomography (CT) scans were obtained through the center of the patellar articular cartilage in 0 degrees of flexion. Three different patellofemoral indices were measured by the second author (K.W.), who was not involved in the clinical examination: lateral patellar displacement (LPD), lateral patellar tilt (LPT), and patella-lateral condyle index (PLCI). These results were compared with the values of the measured Q angle. For statistical analysis, the Pearson correlation coefficient was calculated and the Statistical Package for Social Science (SPSS) used. A pvalue < 0.05 was considered significant. We could not find a significant correlation between the Q angle values and the patellofemoral indices in all patients (bilateral or only right/left). Within the patients with bilateral patellofemoral pain (n = 15), there was a significant correlation between LPD and PLCI (p = 0.015), LPT and PLCI (p = 0.024) left and LPD and LPT(p = 0.011) right. Similar results were found in patients with pain only on one side. In conclusion, there is no significance between the Q angle and the position of patella. The diagnostic relevance of the Q angle could not be established.