Excessive repetitive loading concentrating upon plantar fascia is considered as the most influential factor in plantar fasciitis development. Abnormal foot structure may lead to high risk of plantar fasciitis. However, the biomechanical factor that may cause plantar fasciitis has not been thoroughly investigated. Orthotic device is a common treatment used for plantar fasciitis. However, there is no direct and quantitative data, such as stress and strain distribution of plantar fascia for patient with foot orthosis during gait. Therefore, the aim of this three-year project study is to investigate the biomechanical mechanism of different foot structures and to understand the biomechanical response of plantar fascia during stance phase of gait cycle by dynamic finite element analysis, gait analysis as well as plantar pressure measurement. In addition, the efficacy of foot orthoses will be evaluated by the same research process. The hypotheses are that flat foot and high arch foot may result in higher stress and strain upon plantar fascia during gait; the foot orthosis, such as total contact insole, carbon fiber plate and rocker bottom sole, would reduce stress and strain distribution around the calcaneal medial tuberosity; rigid and curved geometric bottom will be able to relief plantar fascia stretching during push-off phase.

The plantar fascia has long been considered to play an important role in the weight-bearing foot, both in static stance and in dynamic function. Various functional and structural roles have been indicated by virtue of its anatomical attachments. Excessive repetitive loading concentrating upon plantar fascia is considered as the most influential factor in plantar fasciitis development. Abnormal foot structure may lead to high risk of plantar fasciitis. However, the biomechanical factor that may cause plantar fasciitis has not been thoroughly investigated. Orthotic device is a common treatment used for plantar fasciitis. However, there is no direct and quantitative data, such as stress and strain distribution of plantar fascia for patient with foot orthosis during gait. Therefore, the aim of this three-year project study is to investigate the biomechanical mechanism of different foot structures and to understand the biomechanical response of plantar fascia during stance phase of gait cycle by dynamic finite element analysis, gait analysis as well as plantar pressure measurement. In addition, the efficacy of foot orthoses will be evaluated by the same research process.

In this research, a plantar fascia specific finite element foot model with tibia will be reconstructed from magnetic resonance images obtained from subjects with normal foot, flat foot and high arch foot structures. The same subject will also serve for plantar soft tissue material property testing, gait analysis as well as plantar pressure measurement. The kinematic and kinetic data from both gait analysis and plantar pressure measurement will be used to validate the accuracy of dynamic finite element analysis. In addition, 20 normal, 10 flat foot and 10 high-arch foot subjects will also be recruited for gait analysis and plantar pressure measurement. The kinematic and kinetic data from both gait analysis and plantar pressure measurement will be compared with the results of finite element analysis.

Inclusion Criteria:

1. With normal bilateral foot arch structure, unilateral flat foot or unilateral high arch foot
2. With no more musculoskeletal disorders or malalignment
3. With no degeneration of low-extremity joint
4. With no diabetes mellitus or peripheral neuropathy
5. With no injury and pain of low-extremity in recent three month.

Exclusion Criteria:

1. Painful disorders
2. Foot related disorders or deformity
3. Dorsal or plantar wound and trauma
4. Poor proprioception
5. Obvious abnormal gait pattern, such as midfoot strike

Subjects with normal foot structure or abnormal foot structure (flat foot or high arch foot) will be invited to participant this study.