Patellofemoral pain is a common knee disorder that can limit the activity of young adults. The biomechanics of the patellofemoral joint must be better understood to uncover the basic mechanism of the disorder and to design more effective treatments. Although joint geometry and alignment have been evaluated under static conditions or with minimal joint loading, the mechanics of the patellofemoral joint have not been thoroughly investigated during highly-loaded motions. The goal of this dissertation was to measure patellofemoral joint geometry and motion during weight-bearing conditions to improve the diagnosis and treatment of patellofemoral pain.

We developed a technique to measure cartilage thickness in load-bearing regions of the patellofemoral joint We used this technique to estimate patellofemoral joint cartilage thickness in a group of pain-free control subjects and a group of individuals diagnosed with patellofemoral pain. This study revealed that males have thicker cartilage than females on the patella and femur (p<0.05) and males with patellofemoral pain have lower peak cartilage thickness on the patella than pain-free males (p<0.05).

We established the accuracy with which real-time MRI can measure joint kinematics using an MRI-compatible motion phantom with a known and repeatable motion trajectory. We assessed the accuracy of measuring the motion of the phantom in two different scanners and evaluated the dependence of measurement accuracy on movement speed. We found that we could track the motion phantom to within 2mm for speeds of 38mm/s in a 0.5T open-bore MRI scanner and 217mm/s in a 1.5T closed-bore MRI scanner. We used the results of this study to design a protocol for measuring the kinematics of the patellofemoral joint in human subjects with real-time MRI.

We used real-time MRI to measure patellofemoral joint kinematics in vivo during upright, weight-bearing knee extension. To estimate 2D patellofemoral joint kinematics from the real-time images, we developed a semi-automatic tracking technique using normalized cross-correlation to identify bony landmarks in every frame of the real-time image sequence. We estimated joint kinematics in 13 pain-free female subjects and 22 females diagnosed with patellofemoral pain. We also assessed the effects of a knee brace on patellofemoral joint kinematics. Subjects with patellofemoral pain exhibited increased lateral translation of the patella relative to the femur compared to the control subjects for knee flexion angles between full extension and 44° (p<0.05). Our results showed that the knee brace reduced the lateral translation of the patella near full extension (p<0.05), but did not affect the lateral rotation. These results indicate that abnormal joint kinematics may be a cause of patellofemoral pain in some females and could be addressed during treatment.

This dissertation evaluates several of the potential mechanisms of patellofemoral pain and establishes the need to better differentiate the underlying abnormalities present in each patient to design the most effective treatment.