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Abstract
Four male recreational runners, ages 21-39, underwent intracortical pin implantation to study their tibiofemoral (TFJ) and patellofemoral joint (PFJ) kinematics 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 peripatellar pain (PFP). Clusters of four LEDs were attached to each pin in the femur, tibia and patella. The position of the LEDs was recorded via optoelectronic cameras sampling at 100 Hz while subjects ran on a treadmill operating at 3.35 m/s (8 min/mile pace). The SMAC procedure was used to reconstruct the global coordinates of the LEDs. Six DOF kinematics were calculated with respect to a joint coordinate system. Two-dimensional rearfoot data were also collected via a Locam camera operating at 100 fps. The PFP subjects 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. Tibial movements were not found to be dependent upon subtalar joint motion as often suggested in the literature. 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.
Responses to orthotic intervention 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.