Human patellofemoral kinematics and related joint surface geometry

Abnormal patellofemoral tracking has been implicated in the presence of patellofemoral pain syndrome and osteoarthritis. However, results from normal PF studies indicate large inter-limb variability. It is speculated that this variability may be explained with detailed knowledge of the underlying surface geometries. This study presents an externally loaded, dynamic in-vitro leg extension model to collect continuous kinematic data through a range of motion. Cartilage surface data were collected using the multi-station digital photogrammetry (NMPG) technique and represented using a thin plate spline algorithm. Kinematics and surface plots were input into a mathematical model to investigate joint contact. The patellae rotated and shifted laterally with increasing knee flexion with varying magnitudes. Patellar tilt was variable with most limbs exhibiting medial then lateral tilt. Abnormal PF tracking was not always correlated with abnormal contact characteristics. The complex joint contact mechanics were governed by both joint surface geometries and kinematics.