The influence of first ray mobility on forefoot plantar pressure and hindfoot kinematics during walking

Background: Hypomobility and hypermobility of the first ray have been implicated in the literature as a primary cause of mechanical foot problems because of proposed obligatory and compensatory movements. Despite these theoretical links, research is sparse regarding the effect on kinematic and plantar pressure patterns as a result of altered first ray mobility. The purpose of this study was to determine whether hypomobility or hypermobility of the first ray alters hindfoot kinematics or the distribution of plantar pressures during walking. Methods: The magnitude of dorsal first ray mobility in 82 individuals was measured and then classified as being hypomobile, normal, or hypermobile. The plantar pressure under the first and second metatarsal heads, as well as hindfoot kinematics during walking, were then compared between the three categories of first ray mobility. Results: The results of this study indicate that those feet with a hypomobile first ray had significantly decreased plantar force and pressure values under the first metatarsal compared to the second metatarsal. In addition, feet with a hypomobile first ray showed significantly more hindfoot eversion compared to those with either normal or hypermobile first rays. Conclusion: The results of this study do not support the common theoretical implications of altered mobility of the first ray related to plantar pressure and hindfoot kinematics.