Evidence of abnormal anteroposterior patellar tilt in patients with patellar tendinitis with use of a new radiographic measurement

Background: A number of clinical conditions of the patellofemoral joint have been correlated with abnormal patellofemoral radiographic measurements. Hypothesis: An abnormal anteroposterior patellar-tilt angle may be a contributing factor to pathologic conditions of the knee. Study Design: Prospective nonrandomized clinical trial. Methods: The anteroposterior patellar-tilt angle was measured in cadaveric knees to determine the best knee position. The radiographs of normal subjects and patients with patellar tendinitis or patellofemoral pain syndrome were examined for differences in patellar-tilt angle. Results: Cadaveric measurements demonstrated highest intertester and intratester reliability at 30° of knee flexion and neutral femoral rotation. Intratester measurements on normal subjects exhibited high reliability, with a mean anteroposterior tilt angle of 30.8° ± 6.7°. In the patellofemoral pain group the mean anteroposterior tilt angle was 29.1° ± 8.5°; however, for patients with patellar tendinitis, it was 25.6° ± 7.0°, significantly lower than in the normal population. Furthermore, there was no difference between the angles of involved and uninvolved knees of patients with unilateral patellar tendinitis. Conclusion: The anteroposterior patellar-tilt angle is a clinically reliable measurement of patellar tilt in the sagittal plane that can be used to study patellofemoral tilt in a variety of clinical situations. The results of this study demonstrate that patients with patellar tendinitis have abnormal patellar tilt in the sagittal plane.