The relationship between subtalar and knee joint function as a possible mechanism for running injuries

The purposes of the study were: (1) to evaluate the effects of different surfaces on the relationship between subtalar and knee joint function, and (2) to examine/explore alternative approaches to the evaluation of these relationships. Five subjects ran under four different surface conditions of various hardness, while both rear and sagittal view kinematic data were collected (200 Hz). Critical parameters describing the knee angle and rearfoot motion were examined in conjunction with a curve analysis technique which incorporated slope differences and curve correlations. A repeated measure ANOVA design (surface x subject) was used along with single subject procedures. The results of the study support a strong inter-relationship between pronation and knee joint function via tibial rotation and underlined it as a possible mechanism for injury. Moreover, discrete point analysis might not be the most appropriate methodology for evaluating dynamic functions such as rearfoot motion and knee angle. Extreme methodological care must be exercised when evaluating these functions to avoid oversmoothing and/or masking correlations and differences due to differential subject responses and individual variability. The fact that increased impact force facilitated timing discrepancies between subtalar and knee joint function resulting in a transition of the pronation curve from a unimodal to bimodal configuration, is hypothesized as a possible explanation to better understand the inter-relationships among these lower extremity functions and their relationship to running injuries.