THE WINDLASS MECHANISM DURING NORMAL WALKING AND PASSIVE FIRST METATARSALPHALANGEAL JOINT EXTENSION

Objective. To assess the relationship between passive first metatarsop halangeal extension and rearfoot motion during walking on the windlass mechanism. Design. An in vivo study of the windlass mechanism during passive extension of the first metatarsophalangeal joint and walking. Background. Despite theoretical work regarding the windlass mechanism in cadavers, there is little research concerning its in vivo role. Met hods. The amount of first metatarsophalangeal extension and medial lon gitudinal arch movement of the right foot in 20 subjects between the a ge of 22 and 55 years was recorded as they sat with their right hip, k nee and ankle in 90 degrees and their great toe passively extended. In addition, movement of the rearfoot was recorded while they walked. Re sults. The results of this study showed that the windlass mechanism is active during passive extension of the great toe. In addition, subjec ts could be divided into two groups (IMMEDIATE and DELAYED) based upon the timing of when the windlass mechanism began relative to passive e xtension of their first metatarsophalangeal joint. During walking, the DELAYED group was more inverted at heel strike and had a greater magn itude of rearfoot eversion. Conclusions. Two distinct subpopulations o f individuals can be identified by when the windlass mechanism is init iated relative to passive first metatarsalphalangeal extension. Releva nce The fact that the DELAYED ONSET group exhibited a greater magnitud e of rearfoot eversion during walking may be the result of an ineffect ive windlass mechanism resulting in poor stabilization of the midfoot and development of greater tension in the midtarsal intersegmental lig aments. (C) 1998 Elsevier Science Ltd. All rights reserved.