Translation and Psychometric Testing of the Norwegian Foot Functional Index Revised, Short Version.


The aim of this study is to translate into Norwegian and cross-culturally adapt the Foot Functional Index- revised, short version (FFI-RS) according to international guidelines. Furthermore, the reliability and the validity, responsiveness as well as floor and ceiling effect of the Norwegian version of the FFI-RS will be determined.

Full Title of Study: “Translation, Cross-culture Adaption of Foot Functional Index Revised, Short Version (FFI-RS) Into Norwegian. Testing of Psychometric Properties.”

Study Type

  • Study Type: Observational
  • Study Design
    • Time Perspective: Prospective
  • Study Primary Completion Date: December 2021

Detailed Description

Foot Functional Index, revised short version is a foot specific patient reported outcome measurement (PROM) which covers pain, stiffness, activity limitations, disability as well as psychosocial issues.

The aim of this study is to translate into Norwegian and cross-culturally adapt Foot Functional Index revised, short version (NFFI-RS). Furthermore, the reliability, validity, interpretability and responsiveness will be determined.

The Department of Physical Medicine and Rehabilitation at Oslo University Hospital has an ongoing double blind, randomized sham-controlled trial (RCT) comparing the effect of radial extracorporeal shock wave therapy (rESWT), sham rESWT, standardized exercise program and usual care for patients with longstanding plantar fasciopathy (NCT03472989). The testing of the psychometric properties of the NFFI-RS will include totally hundred patients, both from the mentioned RCT as well as patients with other foot diagnosis recruited from our department.

The translation of the original FFI-RS into Norwegian has been done following the official guidelines.

In the test-retest study fifty patients will complete the NFFI-RS at a one week interval.

Smallest detectable change, measurement error, floor and ceiling effects as well as internal consistency will be calculated by using the baseline data. To decide the construct validity we will test the various hypothesis at baseline.

To calculate the responsiveness and the minimal clinically important change three months data will be assessed. Hypothesis testing for correlation with Patient Global Impression of Change Scale will be used to assess the minimal clinically important change and responsiveness of the NFFI-RS.

Clinical Trial Outcome Measures

Primary Measures

  • Foot Functional Index revised short version ( FFI-RS)
    • Time Frame: Baseline, 1 week, 3 months
    • FFI-RS is a foot specific pain and function score. We will evaluate the reliability of the FFI-RS by testing the internal consistency (Cronbach’s Alpha). Furthermore test-retest will be done with a second FFI-RS recording after one week (ANOVA and intraclass correlation coefficient). We will evaluate construct validity with other instruments (RAND and NRS). To test the responsiveness of FFI-RS, we will evaluate the change in FFI-RS from baseline to 3 months with Patient Global Impression of Change score.

Secondary Measures

  • Numeric Rating Scale (NRS)
    • Time Frame: Baseline
    • Change in heel pain (during Activity last week). NRS is a patient reported pain intensity scale ranging from 0 (no pain) to 10 (worst possible pain). NRS will by used for evaluating the construct validity of FFI-RS.
  • RAND-12
    • Time Frame: Baseline
    • Health related quality of life (12 items). RAND-12 will be used for evaluating the construct validity of FFI-RS.
  • Patient Global Impression Of Change Scale (PGIC)
    • Time Frame: 3 months
    • 7-point scale ranging from “very much improved” to “very much worse”. PGIC will be used for evaluating the responsiveness of FFI-RS.

Participating in This Clinical Trial

Inclusion Criteria

  • Patients with pain localized in the foot
  • Patients understanding oral and written Norwegian

Exclusion Criteria

  • Patients without pain in the foot
  • Patients not understanding oral and written Norwegian

Gender Eligibility: All

Minimum Age: 18 Years

Maximum Age: 100 Years

Investigator Details

  • Lead Sponsor
    • Oslo University Hospital
  • Provider of Information About this Clinical Study
    • Principal Investigator: Marianne Mørk, Physical Therapist – Oslo University Hospital
  • Overall Official(s)
    • Aasne F Hoksrud, MD, PhD, Study Director, Oslo University Hospital, Department of Physical Medicine and Rehabilitation
  • Overall Contact(s)
    • Marianne Mørk, PT Msc, +4792019107,

Citations Reporting on Results

Budiman-Mak E, Conrad KJ, Roach KE. The Foot Function Index: a measure of foot pain and disability. J Clin Epidemiol. 1991;44(6):561-70.

Budiman-Mak E, Conrad K, Stuck R, Matters M. Theoretical model and Rasch analysis to develop a revised Foot Function Index. Foot Ankle Int. 2006 Jul;27(7):519-27.

Hays RD, Morales LS. The RAND-36 measure of health-related quality of life. Ann Med. 2001 Jul;33(5):350-7. Review.

Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine (Phila Pa 1976). 2000 Dec 15;25(24):3186-91. Review.

Ferreira-Valente MA, Pais-Ribeiro JL, Jensen MP. Validity of four pain intensity rating scales. Pain. 2011 Oct;152(10):2399-404. doi: 10.1016/j.pain.2011.07.005.

Terwee CB, Bot SD, de Boer MR, van der Windt DA, Knol DL, Dekker J, Bouter LM, de Vet HC. Quality criteria were proposed for measurement properties of health status questionnaires. J Clin Epidemiol. 2007 Jan;60(1):34-42. Epub 2006 Aug 24.

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