The influence of the windlass mechanism on kinematic and kinetic foot joint coupling

Abstract

Background Previous research shows kinematic and kinetic coupling between the metatarsophalangeal (MTP) and midtarsal joints during gait. Studying the effects of MTP position as well as foot structure on this coupling may help determine to what extent foot coupling during dynamic and active movement is due to the windlass mechanism. This study’s purpose was to investigate the kinematic and kinetic foot coupling during controlled passive, active, and dynamic movements. Methods After arch height and flexibility were measured, participants performed four conditions: Seated Passive MTP Extension, Seated Active MTP Extension, Standing Passive MTP Extension, and Standing Active MTP Extension. Next, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: Neutral, Toe Extension, and Toe Flexion. A multisegment foot model was created in Visual 3D and used to calculate ankle, midtarsal, and MTP joint kinematics and kinetics. Results Kinematic coupling (ratio of midtarsal to MTP angular displacement) was approximately six times greater in Neutral heel raises compared to Seated Passive MTP Extension, suggesting that the windlass only plays a small kinematic role in dynamic tasks. As the starting position of the MTP joint became increasingly extended during heel raises, the amount of negative work at the MTP joint and positive work at the midtarsal joint increased proportionally, while distal-to-hindfoot work remained unchanged. Correlations suggest that there is not a strong relationship between static arch height/flexibility and kinematic foot coupling. Conclusions Our results show that there is kinematic and kinetic coupling within the distal foot, but this coupling is attributed only in small measure to the windlass mechanism. Additional sources of coupling include foot muscles and elastic energy storage and return within ligaments and tendons. Furthermore, our results suggest that the plantar aponeurosis does not function as a rigid cable but likely has extensibility that affects the effectiveness of the windlass mechanism. Arch structure did not affect foot coupling, suggesting that static arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.

Chasing footprints in time – reframing our understanding of human foot function in the context of current evidence and emerging insights

“…They also showed that there is minimal elongation in the plantar aponeurosis as the heel rises, supporting the presence of a windlass mechanism during parts of stance. However, as also reported by Caravaggi et al (2010) and Williams et al (2022), the plantar aponeurosis shortens rapidly as the arch recoils in mid to late stance, suggesting a decline in tension (Williams et al, 2022).…”

“…(2010) and Williams et al . (2022), the plantar aponeurosis shortens rapidly as the arch recoils in mid to late stance, suggesting a decline in tension (Williams et al ., 2022).…”

“…the inverse of stiffness) as it can deform through a greater range of motion. This implies that a windlass mechanism is unlikely to function to increase the stiffness of the foot during propulsion (Davis & Challis, 2022; Farris et al ., 2019; Sichting & Ebrecht, 2021; Williams et al ., 2022). We highlight that it is very difficult to make assumptions about stiffness in the human foot without direct measurement of the forces/torques involved.…”

“…These data clearly show the link between foot muscle activation, MTP joint stiffness and ankle push-off power. These recently published papers (Farris et al, 2019(Farris et al, , 2020Sichting & Ebrecht, 2021;Smith et al, 2021Smith et al, , 2022Welte et al, 2018Welte et al, , 2021Williams et al, 2022) provide detailed information on recruitment and methodology, and are hypothesis-driven. Thus, they not only comply with the hypothetico-deductive approach but also display a strong level of confidence in their findings with QATSDD scores >26 (Table S2).…”

Foot form and function: Variable and versatile, yet sufficiently related to predict one from the other

“…However, including deformation data as a predictor of mechanical function, results in drastically reduced accuracy. This could be because the shape deformations under static loading are not as closely related to locomotor function (Farris et al, 2020;Sichting and Ebrecht, 2021;Welte et al, 2018;Williams et al, 2022) as shape alone appears to be. Additionally, the added inter-subject variability and potential noise from unloaded foot shape contained in the deformation data (Schuster et al, 2021) may also contribute to the reduced predictive accuracy.…”