Evaluating the coupling between foot pronation and tibial internal rotation continuously using vector coding.

Excessive pronation, because of its coupling with tibial internal rotation (TIR), has been implicated as a risk factor in the development of anterior knee pain (AKP). Traditionally, this coupling has been expressed as a ratio between the eversion range of motion and the TIR range of motion (Ev/TIR) that occurs during stance. Currently, this technique has not been used to evaluate specific injuries or the effects of sex. In addition, Ev/TIR is incapable of detecting coupling changes that occur throughout stance. Therefore, the purpose of this study was to compare the coupling between eversion and TIR in runners with (n = 19) and without AKP (n = 17) and across sex using the Ev/TIR ratio, and more continuously using vector coding. When using vector coding, significant coupling differences were noted in runners with AKP (34% to 38% stance), with runners with AKP showing relatively more TIR than eversion. Similarly significant differences were noted across sex (14%-25% and 36%-47% stance), with males transitioning from a loading to propulsive coordination pattern using a proximal to distal strategy, and female runners using a distal to proximal strategy. These differences were only detected when evaluating this coupling relationship using a continuous technique such as vector coding.

Midsole thickness affects running patterns in habitual rearfoot strikers during a sustained run.

The purpose of this study was to: (1) investigate how kinematic patterns are adjusted while running in footwear with THIN, MEDIUM, and THICK midsole thicknesses and (2) determine if these patterns are adjusted over time during a sustained run in footwear of different thicknesses. Ten male heel-toe runners performed treadmill runs in specially constructed footwear (THIN, MEDIUM, and THICK midsoles) on separate days. Standard lower extremity kinematics and acceleration at the tibia and head were captured. Time epochs were created using data from every 5 minutes of the run. Repeated-measures ANOVA was used (P < .05) to determine differences across footwear and time. At touchdown, kinematics were similar for the THIN and MEDIUM conditions distal to the knee, whereas only the THIN condition was isolated above the knee. No runners displayed midfoot or forefoot strike patterns in any condition. Peak accelerations were slightly increased with THIN and MEDIUM footwear as was eversion, as well as tibial and thigh internal rotation. It appears that participants may have been anticipating, very early in their run, a suitable kinematic pattern based on both the length of the run and the footwear condition.

Runners with anterior knee pain use a greater percentage of their available pronation range of motion.

"Excessive" pronation is often implicated as a risk factor for anterior knee pain (AKP). The amount deemed excessive is typically calculated using the means and standard deviations reported in the literature. However, when using this method, few studies find an association between pronation and AKP. An alternative method of defining excessive pronation is to use the joints' available range of motion (ROM). The purposes of this study were to (1) evaluate pronation in the context of the joints' ROM and (2) compare this method to traditional pronation variables in healthy and injured runners. Thirty-six runners (19 healthy, 17 AKP) had their passive pronation ROM measured using a custom-built device and a motion capture system. Dynamic pronation angles during running were captured and compared with the available ROM. In addition, traditional pronation variables were evaluated. No significant differences in traditional pronation variables were noted between healthy and injured runners. In contrast, injured runners used significantly more of their available ROM, maintaining a 4.21° eversion buffer, whereas healthy runners maintained a 7.25° buffer (P = .03, ES = 0.77). Defining excessive pronation in the context of the joints' available ROM may be a better method of defining excessive pronation and distinguishing those at risk for injury.

Evaluating runners with and without anterior knee pain using the time to contact the ankle joint complexes' range of motion boundary.

BACKGROUND: Little biomechanical evidence exists to support the association between excessive foot pronation and anterior knee pain (AKP). One issue could be the way excessive pronation has been defined. Recent evidence has suggested that evaluating pronation in the context of the joint's available range of motion (ROM, anatomical threshold) provides greater insight on when pronation contributes to injury. Theoretically, quantifying the amount of time the joint has to respond before reaching end range (neuromuscular threshold) could provide additional insight. Therefore the purpose of this study was to use a neuromuscular threshold, the time to contact (TtC) the ankle joint complex's ROM boundary, to evaluate runners with and without AKP. METHODS: Nineteen healthy and seventeen runners with AKP had their ROM and running biomechanics evaluated. The TtC was calculated using each individual's angular distance from end range (eversion buffer) and eversion velocity. Data were recorded over ten stance phases and evaluated using a one way analysis of variance and 95% confidence intervals. RESULTS: Runners with AKP had significantly shorter TtC the joint's ROM boundary when compared to healthy runners (64.0 ms vs. 35.6 ms, p=0.01). While not statistically significant, this shorter TtC was in large part due to having a smaller eversion buffer, however velocity was found to have a substantial influence on the TtC of select individuals. These results provide evidence that a link between pronation and AKP exists when using anatomical and neuromuscular based thresholds.

Medially posted insoles consistently influence foot pronation in runners with and without anterior knee pain.

Anterior knee pain (AKP) is a common injury among runners and effectively treated with posted insoles and foot orthotics. While clinically effective, the underlying biomechanical mechanisms that bring about these improvements remain debatable. Several methodological factors contribute to the inconsistent biomechanical findings, including errors associated with removing and reattaching markers, inferring foot motion from markers placed externally on a shoe, and redefining segmental coordinate systems between conditions. Therefore, the purpose of this study was to evaluate the influence of medially posted insoles on lower extremity kinematics in runners with and without AKP while trying to limit the influence of these methodological factors. Kinematics of 16 asymptomatic and 17 runners with AKP were collected while running with and without insoles. Reflective markers were attached to the surface of the calcaneus and kept in place (as opposed to detached) between conditions, eliminating the error associated with reattaching markers and redefining segmental coordinate systems. Using these methods, no significant interactions between insole and injury and the main effect of injury were detected (p>0.05); therefore, means were pooled across injury. Insoles, on average, reduced peak eversion by 3.6° (95% confidence interval -2.9° to -4.3°), peak eversion velocity by 53.2°/s (95% confidence interval -32.9 to -73.4) and eversion range of motion by 1.33 (95% confidence interval -0.8 to -1.9). However, while insoles systematically reduced eversion variables, they had small influences on the transverse plane kinematics of the tibia or knee, indicating that they may bring about their clinical effect by influencing other variables.