In order to understand the walking patterns that contribute to the development of bunions, it is helpful to know what happens in a normal walking pattern.
During normal walking, our heel strikes the ground first. Then, as the rest of the foot lands, it pronates (rolls in) allowing the foot to flatten, cushioning the impact. As the heel lifts preparing for push off, the foot supinates (rolls out) creating an arch, making the foot more rigid for efficient propulsion. In some people, during this push off phase, the pressure is off the side of the big toe. This creates a valgus force that contributes to bunions or hallux valgus.
There are a few factors that contribute to this walking pattern:
1 Tight Achilles tendon/calf muscle – as a person rolls over the foot during the stance phase of walking, the ankle has to dorsiflex (motion where the foot flexes towards the shin). When the Achilles tendon or the calf muscle is tight, this dorsiflexion motion is restricted. To compensate for this lack of mobility, the foot may externally rotate. Instead of rolling over the foot, the person rolls off sideways. The other compensation is to pronate or roll the foot in. Both cause the push off to be off the side of the big toe creating a valgus force.
2 Flat feet and overpronation – as discussed above, pronation to flatten the arch during the initial stages of stepping is normal as it cushions the impact of the foot making contact with the ground. However, people with naturally flat feet or people that overpronate continue to pronate while they should be supinating the foot in preparation for propelling the body forward. This means the foot is still in its “flexible” state with less stability for the force on the big toe during push off. As well, since the foot is rolled in, the weight is more on the big toe and second toe. The push off is sideways creating a valgus force.
3 Weak intrinsic foot muscles and tibialis posterior muscle – the small muscles in the feet and the tibialis posterior help to support the arch of the foot. Weakness of these muscles is one of the factors contributing to overpronation (as discussed above).
4 Weak gluteal muscles – the gluteus medius is a muscle that gives stability to the pelvis when we stand on one leg. If the gluteus medius is weak, the pelvis drops and the knee falls inward (valgus knee) when standing on one leg. In a chain reaction effect, this rolling in of the knee also leads to overpronation of the foot as discussed above.
The next blog, Bunions Part 4 will discuss the Physical Therapy treatment of bunions.
1 Physiopedia website available at: https://physio-pedia.com/Hallux_Valgus
2 OrthoInfo website available at: https://orthoinfo.aaos.org/en/diseases–conditions/bunions/
3 Nix SE, Vicenzino BT, Collins NJ, Smith MD. Gait parameters associated with hallux valgus: a systematic review. J Foot Ankle Res. 2013;6(1):9. Published 2013 Mar 12. doi:10.1186/1757- 1146-6-9
4 Glasoe WM. Treatment of progressive first metatarsophalangeal hallux valgus deformity: A biomechanical based muscle strengthening approach. J Orthop Sports Phys Ther. 2016;46(7): 596- 605.