The effect of internal and external foot rotation on the adduction moment and lateral–medial shear force at the knee during gait

Training multi-parameter gaits to reduce the knee adduction moment with data-driven models and haptic feedback

The purpose of this study was to evaluate gait retraining for reducing the knee adduction moment. Our primary objective was to determine whether subject-specific altered gaits aimed at reducing the knee adduction moment by 30% or more could be identified and adopted in a single session through haptic (touch) feedback training on multiple kinematic gait parameters. Nine healthy subjects performed gait retraining, in which data-driven models specific to each subject were determined through experimental trials and were used to train novel gaits involving a combination of kinematic changes to the tibia angle, foot progression and trunk sway angles. Wearable haptic devices were used on the back, knee and foot for real-time feedback. All subjects were able to adopt altered gaits requiring simultaneous changes to multiple kinematic parameters and reduced their knee adduction moments by 29-48%. Analysis of single parameter gait training showed that moving the knee medially by increasing tibia angle, increasing trunk sway and toeing in all reduced the first peak of the knee adduction moment with tibia angle changes having the most dramatic effect. These results suggest that individualized data-driven gait retraining may be a viable option for reducing the knee adduction moment as a treatment method for early-stage knee osteoarthritis patients with sufficient sensation, endurance and motor learning capabilities.

Self-reported knee and foot alignments in early adult life and risk of osteoarthritis

OBJECTIVE

To determine whether self-reported early adult life malalignment of knees or feet are risk factors for knee or hip osteoarthritis (OA).

METHODS

Participants in the Genetics of Osteoarthritis and Lifestyle case-control database were sent a questionnaire (n = 3,022) containing line-drawing instruments for self-reported knee and foot alignment at ages 20-29 years. Respondents were categorized as having straight, valgus, or varus knee, and straight, toe-in, or toe-out feet. Radiographic criteria were used to define current isolated knee or hip OA, combined knee and hip OA, or non-OA controls. Odds ratios (ORs), adjusted ORs, and 95% confidence intervals (95% CIs) were calculated and logistic regression was performed.

RESULTS

The response rate was 72%; 87.5% of responders (n = 1,901) completed the alignment questions. Increased risk of isolated knee OA occurred with early adult varus (adjusted OR 5.16, 95% CI 2.87-9.41) and valgus knees (adjusted OR 3.16, 95% CI 1.04-9.64). The positive association between knee OA and toe-in foot was explained by varus knee. There was an increased risk of combined knee/hip OA from varus (adjusted OR 4.52, 95% CI 2.39-8.53) and valgus knees (adjusted OR 3.07, 95% CI 0.99-9.54). Varus knee was associated with risk of medial tibiofemoral OA, whereas valgus knee was associated with risk of lateral tibiofemoral and lateral patellofemoral OA. Toe-out foot was associated with reduced medial patellofemoral OA. For knee OA, a multiplicative interaction analysis between occupational risks and varus/valgus yielded an OR(int) of 3.20 (95% CI 1.08-9.49).

CONCLUSION

Constitutional alignment of the leg in terms of varus or valgus knee or foot rotation may be a significant factor in determining development and distribution of knee but not hip OA.

The free moment in walking and its change with foot rotation angle

BACKGROUND

This investigation characterized the time-history pattern of the free moment (FM) during walking and, additionally, assessed whether walking with either an internally or externally rotated foot position altered the FM's time-history.

METHODS

Force plate and foot kinematic data were acquired simultaneously for 11 healthy subjects (6 males, 5 females) while walking at their self-selected comfortable speed in 3 foot rotation conditions (normal, internal and external). The FM was calculated and normalized by the product of each participant's body weight and height prior to extraction of peak FM, occurrence of peak FM in stance and net relative impulse. Differences in these values across foot rotation conditions were assessed using separate one-way, repeated measures analysis of variance and subsequent pair-wise comparisons.

RESULTS

The average FM pattern during normal walking exhibits a biphasic shape: resisting inward rotation during approximately the first half of stance and outward rotation during the latter part of stance. While no differences in peak FM or net relative impulse were observed between the internal foot rotation condition and normal walking, the external foot rotation condition resulted in significantly greater peak FM and relative net impulse in comparison to normal walking.

CONCLUSION

The differences in selected FM variables between normal walking and the external foot rotation condition are attributable to individual subject response to walking with an externally rotated foot. In this condition, some subjects displayed a FM pattern that was similar to that recorded during normal walking, while others displayed markedly larger FM patterns that are comparable in magnitude to those reported for running. The larger FM values in these latter subjects are speculated to be a result of excessive transverse plane body movements. Whilst further investigation is warranted regarding the FM time-history characteristics during walking, our results indicate that the FM may provide useful information in assessment of gait.

Effect of foot rotation on knee kinetics and hamstring activation in older adults with and without signs of knee osteoarthritis

BACKGROUND

To determine the effects of changing the natural foot progression angle during gait (internal and external foot rotation) on the knee's adduction moment, lateral-medial shear force, and the ratio of medial-lateral hamstring muscle activation in those with signs of knee osteoarthritis and a matched healthy control group.

METHODS

Twelve subjects with signs of knee osteoarthritis and 12 matched healthy control subjects were evaluated. A 3D gait analysis system calculated forces and moments at the knee while the subjects walked in three conditions: (1) normal foot position, (2) external foot rotation, (3) internal foot rotation. Medial and lateral hamstring EMG data was also collected simultaneously and used to calculate the medial-lateral hamstring activation ratio during the stance phase of the gait cycle. Repeated measures ANOVAs were used to compare foot rotation conditions within each group; while between group comparisons were performed in the normal rotation condition only using t-tests.

FINDINGS

Those with knee osteoarthritis (OA) had an increased late stance knee adduction moment and a decreased medial-lateral hamstring activation ratio as compared to the healthy control group. Also, external foot rotation decreased the late stance knee adduction moment, lateral-medial shear force, and hamstring activation ratio. However, internal foot rotation did not increase these measures.

INTERPRETATION

Changes in foot position during gait have the ability to alter both the external loading of the knee joint and hamstring muscle activation patterns during gait. This may have implication in helping to unload the knee's articular cartilage.