Four male recreational runners, ages 21-39, underwent intracortical pin implantation so that their tibiofemoral (TFJ) and patellofemoral joint (PFJ) kinematics could be studied during treadmill running. Two of the subjects demonstrated normal rearfoot mechanics and had no history of lower extremity pathology over the past 2 years (NL). The other two subjects exhibited excessive subtalar joint pronation and had a history of undiagnosed and untreated peripatellar pain (PFP). Clusters of four LEDs were attached to each pin in the femur, tibia and patella. The position of the LEDs in image space was recorded via optoelectronic cameras and a computer while subjects ran on a treadmill operating at 3.35 m/s (8 min/mile pace). Using the SMAC procedure, especially modified for this study, the clusters served to "self-calibrate" the experimental area and allow for reconstruction of their global coordinates. Custom software was written to determine the 6 DOF kinematics and transform them from a global to anatomical coordinate system. Two-dimensional rearfoot data were also collected via a Locam camera operating at 100 fps. The PFP subjects in this study were prescribed foot orthoses in response to their overpronation and comparisons were made between their orthotic and non-orthotic conditions.

Tibiofemoral and patellofemoral kinematics did exhibit subtle differences between the NL and PFP subjects. Differences seen at the patellofemoral joint were often on the order of 3-4 degrees or 3-4 mm. These could result in different patellofemoral contact profiles leading to abnormal pressures at the articular surfaces. These data, however, do not support the notion that the tibial movements are dependent upon subtalar joint motion as often suggested in the literature. It was clearly shown that greater subtalar pronation did not result in greater tibial internal rotation. The delay in peak tibial internal rotation seen in the PFP subjects with respect to both time of footstrike and peak subtalar joint pronation deserves further investigation as it may play a role in compensation for their excessive pronation.

Orthotic intervention resulted in some kinematic changes in both of the subjects. However, their responses were quite different despite very similar orthotic prescriptions. This emphasizes the expression of individuality which may reflect differences in factors such as neuromuscular status and anatomy. A general trend for both increased velocity and variability was noted in the PFP subjects in the non-orthotic condition. This may indicate less control of movement in these subjects. A tendency for a decrease in variability was noted in the orthotic condition suggesting enhanced stability.