The Immediate Effect of Lateral Wedging on First Metatarsophalangeal Joint Kinematics and Centre of Pressure

Abstract

Background Lateral wedges are often prescribed to increase the first metatarsophalangeal joint (MPJ) range of motion or alter the centre of pressure (COP) in the foot. This study explored the effect of lateral wedge design and placement on first MPJ extension and COP during walking and running gait. Methods A randomised crossover design was used and 24 healthy participants ran and walked in 10 insole conditions comprising differing combinations of inclination, placement and contour. First MPJ extension and foot COP were examined. Time-series data were analysed across the stance phase using statistical parametric mapping. Results Lateral wedges significantly reduced first MPJ extension during both walking (p < 0.001; 100% of stance) and running (p = 0.004; 14–72%, and p = 0.017; 76–99% of stance). Similarly, lateral wedge placement reduced first MPJ joint extension during walking (p < 0.001; 100% of stance) and running (p = 0.003; 13–69%, and p = 0.012; 78–100%). Full-length or 6° lateral wedges shifted the COP medially relative to the midline of the foot (p = 0.01). Compared to sham, lateral wedges placed on contoured insoles exhibited a smaller reduction in first MPJ during walking (p = 0.008) and shifted the COP medially during both walking (p < 0.001) and running (p = 0.020). Conclusion Where the intention of using lateral wedging is to shift the COP medially, these data indicate that a wedge which is of higher inclination (6°) or spanning the full-length of the insole, should be used. Conversely, if the goal is to reduce extension at the first MPJ, these findings suggest that both 3° and 6° inclination wedges are suitable, with either forefoot or full-length applications proving effective.