(1) Background: Plantar heel pain (PHP), a common overuse foot injury, significantly impacts runners. While the mechanical role of the plantar fascia during gait is established, its effect on foot function during running, particularly foot joint coupling, remains unclear. This study investigated foot joint coupling during running in runners with and without PHP using statistical parametric mapping (SPM). (2) Methods: Thirteen uninjured runners (seven m, six f; age = 30.5 ± 5.9 years; BMI = 23.5 ± 3.0 kg/m²) and thirteen runners with PHP (six m, seven f; age = 29.0 ± 8.0 years; BMI = 23.1 ± 2.0 kg/m²) performed running trials at 4.0 m/s. A seven-segment foot model that defined six functional articulations (rearfoot, medial and lateral midfoot, medial and lateral forefoot, first metatarsophalangeal) was used to quantify foot kinematics, vector coding was used to calculate joint coupling between adjacent foot segments, and SPM was used to analyze joint stance phase coupling angles. (3) Results: There were statistically significant differences in rearfoot frontal plane–medial midfoot frontal plane joint coupling between runners with and without PHP from 69 to 70% stance phase (mean difference = 39.41°) and at 76% stance (mean difference = 47.89°). The differences were indicative of greater medial midfoot eversion rotation relative to rearfoot complex inversion in the PHP group. (4) Conclusions: The difference in the rearfoot complex and medial midfoot frontal plane coupling occurred during the propulsion phase of the running stance when the foot should be transitioning to a more supinated position, which may reflect compromised supination due to plantar fascia degeneration.

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Background: Older adult falls during step negotiation result in higher injury rates compared to level ground falls. Previous research on discrete events during step negotiations may not capture important age-related changes. Curve analysis techniques enable assessment of an entire time series and may further advance the understanding of older adult falls during step negotiation. The purpose of the current study was to investigate lower extremity kinematics during transition step negotiation in older women with fall history compared to young women using statistical parametric mapping (SPM). Methods: 15 older female adults with a fall history and 15 young female adults participated in the study. Participants performed walking trials along a 5.5 m raised walkway, descended a 17 cm step and continued walking 3 m. Data was processed from lead limb toe-off prior to the step, through lead limb weight acceptance of the transition step. SPM was used to perform independent t-test analysis of the three-dimensional lower extremity time series. Results: The older faller group showed significantly decreased lead hip abduction (9–19% of step negotiation, mean difference: 3.74°, p = 0.045), increased lead knee flexion (65–80% of step negotiation, mean difference: 5.8°, p = 0.012), and increased trail limb hip adduction (91–100% of step negotiation, mean difference: 3.92°, p = 0.046). Conclusions: The older faller group showed altered hip joint angles in the frontal plane and knee joint angles in the sagittal plane during early swing and late weight acceptance phases, which may reflect compensatory strategies for reduced strength and/or balance. Curve analysis provides additional insight into age-related kinematic changes during step negotiation that may be related to older adult fall risk.