Foot and Ankle Joint Biomechanical Adaptations to an Unpredictable Coronally Uneven Surface

Coronally uneven terrain, a common yet challenging feature encountered in daily ambulation, exposes individuals to an increased risk of falling. The foot-ankle complex may adapt to improve balance on uneven terrains, a recovery strategy which may be more challenging in patients with foot-ankle pathologies. A multisegment foot model (MSFM) was used to study the biomechanical adaptations of the foot and ankle joints during a step on a visually obscured, coronally uneven surface. Kinematic, kinetic and in-shoe pressure data were collected as ten participants walked on an instrumented walkway with a surface randomly positioned ±15 deg or 0 deg in the coronal plane. Coronally uneven surfaces altered hindfoot-tibia loading, with more conformation to the surface in early than late stance. Distinct loading changes occurred for the forefoot-hindfoot joint in early and late stance, despite smaller surface conformations. Hindfoot-tibia power at opposite heel contact (@OHC) was generated and increased on both uneven surfaces, whereas forefoot-hindfoot power was absorbed and remained consistent across surfaces. Push-off work increased for the hindfoot-tibia joint on the everted surface and for the forefoot-hindfoot joint on the inverted surface. Net work across joints was generated for both uneven surfaces, while absorbed on flat terrain. The partial decoupling and joint-specific biomechanical adaptations on uneven surfaces suggest that multi-articulating interventions such as prosthetic devices and arthroplasty may improve ambulation for mobility-impaired individuals on coronally uneven terrain.