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.

Study 1: Comparative Study of Gait and Foot Segment Motion Between Individuals with Plantar Fasciitis and Healthy Controls

Inclusion Criteria (PF Group):

• Aged 20-80 years

• Plantar fasciitis (PF) symptoms for at least one month

• Pain or tenderness at the medial calcaneal tubercle or proximal plantar fascia

• At least one of the following symptoms:

  • Morning pain (first steps in the morning)
  • Pain after prolonged sitting
  • Pain during weight-bearing activities

Exclusion Criteria (PF Group):

• Other painful conditions in the lower extremity or back
• History of rheumatoid arthritis
• Neurological or vascular diseases
• Leg length discrepancy >1 cm
• Severe pain preventing walking

Inclusion Criteria (Healthy Controls):

• No current or previous history of PF symptoms
• No foot pain

Exclusion Criteria (Healthy Controls):

• Same as those listed for the PF group

Study 2: Translation and Validation of the Thai Version of the Foot Function Index (FFI-Th) Inclusion Criteria (Individuals with plantar problems)

• Aged 20-80 years
• Experienced plantar foot pain or tenderness for at least one month (at rest or during weight-bearing activities)
• Able to read and communicate in Thai
• No uncorrected visual impairments Exclusion Criteria (Individuals with plantar problems)
• Pain in other areas of the lower extremities
• History of systemic inflammatory diseases
• History of neurological diseases
• Received any treatment during the study period

Study 3: Effects of Strengthening and Stretching Exercise Programs on Pain and Gait in Patients with Plantar Fasciitis: A Randomized Controlled Trial Inclusion Criteria:

• Aged 20-80 years
• Heel pain lasting more than one month
• Pain during the first steps in the morning or after rest
• Tenderness at the medial calcaneal tubercle
• Plantar fascia thickness greater than 4.0 mm (confirmed by ultrasound)

Exclusion Criteria:

• History of back or lower limb surgery within 6 months

• Recent trauma or corticosteroid injections (within 6 months)

• Leg length discrepancy greater than 1 cm

• Pregnancy

• Inability to perform the exercise program

• Receiving other ongoing treatments or performing other foot-specific exercises

• Coexisting conditions including:

  • Achilles tendinopathy
  • Acute ankle sprain
  • Tarsal tunnel syndrome
  • Patellofemoral syndrome
  • Calcaneal spurs
  • Heel pad syndrome

3 months in total per participants. Adverse events were monitored over a total of 3 months, which includes a 4-week (1-month) intervention phase plus a subsequent 2-month follow-up phase.

This study did not compare to the pure conservative physical therapy treatment, which may provide more information about the effectiveness of strengthening and stretching exercises that may superior to the conservative treatment alone.

Conservative physical therapy intervention was launched by the same physical therapist who blind to participant group allocation.