Are flexible flat feet associated with proximal joint problems in children?

The role of flexible flat feet (FF) in the development of musculoskeletal symptoms at joints proximal to the ankle is unclear. We undertook an observational study to investigate the relationship between foot posture and the proximal joints in children. It was hypothesised that reduced arch height would be associated with proximal joint symptoms and altered gait kinematics and kinetics particularly in the transverse plane at the hip and knee. Ninety-five children between the ages of 8-15 were recruited into this ethically approved study. Foot posture was classified using the arch height index (AHI). The frequency of knee and hip/back pain was documented, and each child underwent three dimensional gait analysis. Reduced arch height was associated with increased odds of knee symptoms (p < 0.01) and hip/back symptoms (p = 0.01). A flat foot posture was also significantly associated with a reduction in the second peak of the vertical ground reaction force (p = 0.03), which concomitantly affected late stance hip and knee moments. A reduced AHI was also associated with increased pelvic retraction and increased knee valgus in midstance. No kinematic and kinetic parameter associated with a flat foot posture related to increased proximal joint symptoms in the FF group. Children with a flatter foot posture are more likely to have pain or discomfort at the knee, hip and back; however, the mechanisms by which this occurs remain unclear. Treating FF without explicit understanding of how it relates to symptoms is difficult, and further work in this area is required