Role of plantar fascia in the load bearing capacity of the human foot.

Plantar fascia release is an accepted and widely used surgical way to reduce heel pain, however its effect of the load bearing characteristics of the foot is not well studied. A simple biomechanical model is developed here to analyze load bearing mechanism of the foot during the stance phase of the gait cycle. Quasilinearization is used for the system identification, and all model's parameters are determined from the in vivo tests. The model is used to compare the load bearing mechanism of different pathological situations. The results of the study suggest that the plantar fascia carries as much as 14% of the total load on the foot. Its surgical release decreases dynamic loading on the ankle by only 10%. It is also found that the lowering of the arch degenerates the load bearing capacity of the foot. Thus, the plantar fascia plays an important part in the load bearing by the foot and its surgical release should be carefully considered.