STUDY DESIGN: Controlled laboratory study using a cross-sectional design. OBJECTIVES: To compare patellofemoral joint kinematics, femoral rotation, and patella rotation between females with patellofemoral pain (PFP) and pain-free controls using weight-bearing kinematic magnetic resonance imaging. BACKGROUND: Recently, it has been recognized that patellofemoral malalignment may be the result of femoral motion as opposed to patella motion. METHODS: Fifteen females with PFP and 15 pain-free females between the ages of 18 and 45 years participated in this study. Kinematic imaging of the patellofemoral joint was performed using a vertically open magnetic resonance imaging system. Axial-oblique images were obtained using a fast gradient-echo pulse sequence. Images were acquired at a rate of 1 image per second while subjects performed a single-limb squat. Measures of femur and patella rotation (relative to the image field of view), lateral patella tilt, and lateral patella displacement were made from images obtained at 45°, 30°, 15°, and 0° of knee flexion. Group differences were assessed using a mixed-model analysis of variance with repeated measures. RESULTS: When compared to the control group, females with PFP demonstrated significantly greater lateral patella displacement at all angles evaluated and significantly greater lateral patella tilt at 30°, 15°, and 0° of knee flexion. Similarly, greater medial femoral rotation was observed in the PFP group at 45°, 15°, and 0° of knee flexion when compared to the control group. No group differences in patella rotation were found. CONCLUSION: Altered patellofemoral joint kinematics in females with PFP appears to be related to excessive medial femoral rotation, as opposed to lateral patella rotation. Our results suggest that the control of femur rotation may be important in restoring normal patellofemoral joint kinematics.

J Orthop Sports Phys Ther 2010;40(5):277-285, Epub 12 March 2010. doi:10.2519/jospt.2010.3215

KEY WORDS: biomechanics (lower extremity), hip, knee, medical imaging, MRI

Study Design: Single-group, repeated-measures design. Objective: To compare patellofemoral joint kinematics during weight-bearing and non–weight-bearing knee extension in persons with lateral subluxation of the patella. Background: The only previous study to quantify differences in patellofemoral joint kinematics during weight-bearing and non–weight-bearing tasks was limited in that static loading conditions were utilized. Differences in patellofemoral joint kinematics between weight-bearing and non–weight-bearing conditions have not been quantified during dynamic movement. Methods and Measures: Six females with a diagnosis of patellofemoral pain and lateral subluxation of the patella participated. Using kinematic magnetic resonance imaging, axial images of the patellofemoral joint were obtained as subjects extended their knees from 45° to 0° during non–weight-bearing (5% body weight resistance) and weight-bearing (unilateral squat) conditions. Measurements of patellofemoral joint relationships (medial/lateral patellar displacement and patellar tilt), as well as femur and patella rotations relative to an external reference system (ie, the image field of view), were obtained at 3° increments during knee extension. Results: During non–weight-bearing knee extension, lateral patellar displacement was more pronounced than during the weight-bearing condition between 30° and 12° of knee extension, with statistical significance being reached at 27°, 24°, and 21°. No differences in lateral patellar tilt were observed between conditions (P = .065). During the weight-bearing condition, internal femoral rotation was significantly greater than during the non–weight-bearing condition as the knee extended from 18° to 0°. During the non–weight-bearing condition, the amount of lateral patellar rotation was significantly greater than during the weight-bearing condition throughout the range of motion tested. Conclusions: The results of this study demonstrated that lateral patellar displacement was more pronounced during non–weight-bearing knee extension compared to weight-bearing knee extension in persons with lateral patellar subluxation. In addition, the results of this investigation suggest that the patellofemoral joint kinematics during non–weight-bearing could be characterized as the patella rotating on the femur, while the patellofemoral joint kinematics during the weight-bearing condition could be characterized as the femur rotating underneath the patella.

J Orthop Sports Phys Ther. 2003;33(11):677-685.
 

Key Words: magnetic resonance imaging, patellar tracking, patellofemoral joint