Plantar Heel Pain: Multisegment Foot Motion and Muscle Function, FFI Translation, and Evaluation of Treatments

Overview

Plantar fasciitis (PF) is a prevalent musculoskeletal condition of plantar heel pain (PHP) that leads to pain, functional limitations, and reduced quality of life, especially among active adults aged 25 to 65. Understanding the biomechanical alterations in foot motion among individuals with PF is essential to inform targeted treatment strategies and prevent symptom chronicity. However, research exploring detailed multi-segment foot motion changes in this population remains limited. Assessing foot function is a key component in understanding symptom development and treatment outcomes. The Foot Function Index (FFI) is an internationally recognized, reliable, and valid questionnaire used to measure foot pain and disability. To facilitate its use in Thai populations and enable cross-cultural comparisons, it is crucial to translate and validate the FFI into Thai. Although exercise interventions such as strengthening and stretching are widely used to manage PHP, evidence regarding their relative effectiveness on pain reduction and gait improvement is inconclusive. Rigorous evaluation of these programs is needed to establish evidence-based guidelines for physical therapy in this population. Study 1: Comparative Study of Gait and Foot Segment Motion Between Individuals with Plantar Fasciitis and Healthy Controls This study aimed to compare multi-segment foot motion during walking between individuals with plantar fasciitis (PF) and healthy controls. A matched case-control design was used, with gait data collected via a 3D motion capture system and analyzed using the Oxford Foot Model. Study 2: Translation and Validation of the Thai Version of the Foot Function Index (FFI-Th) This study aimed to translate the Foot Function Index (FFI) into Thai (FFI-Th) and evaluate its psychometric properties individuals with plantar foot complaints. Study 3: Effects of Strengthening and Stretching Exercise Programs on Pain and Gait in Patients with Plantar Fasciitis: A Randomized Controlled Trial This study aimed to investigate the effects of physical therapy interventions-specifically strengthening versus stretching exercise programs-on pain and temporospatial gait parameters in patients with PF.

Procedure Study 1: Comparative Study of Gait and Foot Segment Motion Between Individuals with Plantar Fasciitis and Healthy Controls A matched case-control study recruited individuals with PF and matched healthy controls by age, gender, weight, and height. After informed consent, anthropometric data were collected, and participants wore tight clothing to allow accurate marker placement. Forty-two reflective markers were attached to define foot and lower limb segments following the Oxford Foot Model and Plug-In-Gait protocols. A static calibration trial was recorded, after which some markers were removed. Then, participants performed walking trials along an 8-meter walkway while motion capture cameras and force plates recorded kinematic and kinetic data simultaneously. Each participant completed 3-5 gait trials at a self-selected comfortable speed, with two trials matching the control group's gait speed and cadence selected for analysis. Data were filtered and normalized over the gait cycle for further assessment. Outcome measures included ground reaction forces (GRFs) during braking and propulsion phases and peak multi-segment foot joint angles in three planes. Study 2: Translation and Validation of the Thai Version of the Foot Function Index (FFI-Th) This study used a cross-sectional design to translate and validate the Foot Function Index (FFI) into Thai (FFI-Th) following a standardized cross-cultural adaptation process. The steps included independent forward translation by two bilingual translators, synthesis by an expert committee, backward translation by two native English speakers, harmonization through consensus meetings, cognitive interviews with 20 individuals to ensure clarity, and final proofreading by a linguist. To assess criterion validity, participants also completed the EuroQol five-dimensional questionnaire (EQ-5D-5L) for health-related quality of life and a pain visual analogue scale (pain-VAS). These instruments provided comparative data for evaluating the FFI-Th's validity. Study 3; Effects of Strengthening and Stretching Exercise Programs on Pain and Gait in individuals with Plantar Fasciitis: A Randomized Controlled Trial This double-blind, randomized controlled trial was used. Individuals with PF were screened and recruited based on specific inclusion and exclusion criteria. After obtaining informed consent, participants were randomly assigned into two groups: strengthening exercises or stretching exercises. All participants received a standardized physical therapy treatment including therapeutic ultrasound and manual therapy, followed by their assigned exercise programs instructed by blinded physical therapists. Participants performed home-based exercises three times daily for 4 weeks, then continued at home for 2 months with exercise logs to monitor compliance. Outcome assessments were conducted five times: baseline, mid-intervention, post-intervention, and at 1- and 2-month follow-ups. Data collected included demographics, pain intensity via visual analogue scale (VAS), and temporospatial gait parameters measured by a force distribution platform and synchronized video system.