FAST and PSFS: Assessment and Validation of Two Functional Scales in Patients With Knee OA in Singapore

Functional Activity Scoring Tool (FAST) and Patient-Specific Functional Scale (PSFS): Assessment and Validation of Two Functional Scales in Patients With Knee Osteoarthritis (OA) in Singapore

The new National One-Rehab framework mandates the use of the Patient-Specific Functional Scale (PSFS) as an outcome measure to track patients' rehabilitation progress. Anecdotally, we have encountered patients (especially elderly ≥ 65 years old) with difficulty understanding and completing such questionnaire accurately. We developed a pictorial functional scale (Functional Activity Scoring Tool, FAST) with reference to the successful application of the Wong-Baker FACES pain rating scale. Concurrently, we hope to validate PSFS and FAST against Knee injury and Osteoarthritis Outcome Score (KOOS) which is validated in Singapore population.

This study aims to investigate the reliability and validity of the PSFS and FAST in patients with knee osteoarthritis. We hypothesize that both the PSFS and FAST can be used to measure difficulty in performing activities of daily living in patients with knee osteoarthritis in a reliable and valid manner.

The FAST and PSFS questionnaires will be administered to patients in SingHealth Polyclinics with knee osteoarthritis to explore the psychometric and clinimetric properties. Eligibility criteria were: age 45 and above, proficient in English, diagnosed with knee osteoarthritis. Patients were excluded if they have underlying medical or trauma conditions (i.e., trauma, fracture, infection, inflammatory disease, tumor), history of knee surgery within the last 3 months, or clinically recognizable cognitive impairment.

Eligible patients will be informed about the purpose of the study and the confidentiality and anonymity of the process. After giving written consent they will complete a questionnaire on demographic and clinical characteristics and the sets of outcome measures (FAST, KOOS, PSFS). Participants will then return at two-to-three weeks later to complete the sets of outcome measures again and GROC, and to state their preferred outcome measures. Statistical analysis will be conducted to evaluate the validity and reliability of PSFS and FAST against KOOS.

Study Overview

• Status: Completed
• Conditions: Knee Osteoarthritis
• Intervention / Treatment: Other: Physiotherapy

Detailed Description

Validation

The FAST and PSFS questionnaires will be administered to patients in SingHealth Polyclinics (SHP) with knee osteoarthritis to explore the psychometric and clinimetric properties. Eligibility criteria were: age 45 and above, proficient in English, diagnosed with knee osteoarthritis. Patients were excluded if they have underlying medical or trauma conditions (i.e., trauma, fracture, infection, inflammatory disease, tumor), history of knee surgery within the last 3 months, or clinically recognizable cognitive impairment. Statistical analysis will be conducted to evaluate the validity and reliability of PSFS and FAST against KOOS.

Questionnaire

1. FAST

   FAST is developed by Mr. Tang Zhi Yin and Mr. Ng Khim Siong from SHP physiotherapy department. It is a pictorial scale with 7 emotion faces (different degrees of sadness to happiness) on stairs to depict corresponding level of difficulty a patient is experiencing during performing activity. Short descriptions are labelled under the faces, as well as a scale of 0-10 to guide the patient to rate his/her functional difficulty. The patient is asked to identify up to 3 activities that being affected due to his/her current musculoskeletal pain, and to rate each activity on the FAST.

2. PSFS

   The PSFS is a self-reported, patient-specific measure that assesses patients' functional status. Patients are asked to identify three activities that are most affected by their condition and then rate their ability on a 0-10 scale, where 0 is unable to perform activity and 10 is able to perform activity at the same level as before the onset of symptoms.

3. KOOS

   The KOOS is a knee-specific instrument, developed to assess the patients' opinion about their knee and associated problems. It is a validated tool in Singapore for knee osteoarthritis patients. It has a total of 42 items in 5 subscales i.e., pain, other symptoms, function in daily living, function in sport and recreation, and knee-related quality of life. Scores are interpreted independently for each subscale. As our study focuses on function, we only apply subscales for function in daily living, function in sport and recreation, and knee-related quality of life.

4. GROC

The GROC is an outcome measure that assesses patients' self-perception of change in their condition between sessions. Participants were asked to rate the change in their condition on a 15-point transitional scale from -7 (a very great deal worse) to 7 (a very great deal better). The GROC scale is easy to administer, requires minimal skills or training, has good reproducibility, and is sensitive to change.

Data collection

Eligible patients will be informed for the purpose of the study and the confidentiality and anonymity of the process. After giving written consent they will complete a questionnaire on demographic and clinical characteristics and the sets of outcome measures (FAST, KOOS, PSFS). Participants will then return at two-to-three weeks later to complete the sets of outcome measures again and GROC, and to state their preferred outcome measures.

Statistical analysis

All statistical analysis will be conducted using SPSS 26 for Windows. To investigate validity, the discriminant validity was evaluated by the Spearman correlation coefficient according to the following criteria: high (rho ≥ 0.60); moderate (rho < 0.60 - ≥ 0.30); or low (rho <0.30). To analyze the test-retest reliability, the intraclass correlation coefficient (ICC) is calculated. An ICC value of less than 0.40 indicated poor reliability, whereas values between 0.40 and 0.75 indicated fair to good reliability; an ICC value of greater than 0.75 showed excellent reliability.

• Study Type: Observational
• Enrollment (Actual): 150

Contacts and Locations

Study Locations

• Singapore
  • Singapore, Singapore
    • SingHealth Polyclinics

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 45 years to 100 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Patients with knee osteoarthritis

Description

Inclusion criteria:

• individuals above the age of 45
• proficient in colloquial/conversational English
• diagnosed with knee osteoarthritis.

Exclusion criteria:

• additional underlying medical or trauma conditions of the knees (e.g., trauma, fracture, infection, inflammatory disease, tumour)
• history of knee surgery within the last three months
• clinically recognizable cognitive impairment that inhibits the completion of the questionnaires.

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Prospective

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Patients with knee osteoarthritis; Individuals who are medically diagnosed with knee osteoarthritis and eligible for physiotherapy care in SingHealth Polyclinics will be recruited. Inclusion criteria include: individuals above the age of 45, proficient in colloquial/conversational English, and diagnosed with knee osteoarthritis. Exclusion criteria include additional underlying medical or trauma conditions of the knees (e.g., trauma, fracture, infection, inflammatory disease, tumour), history of knee surgery within the last three months, or clinically recognizable cognitive impairment that inhibits the completion of the questionnaires.

Other: Physiotherapy; routine referral-based physiotherapy treatment for patients with knee osteoarthritis

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in functional status as assessed by Functional Activity Scoring Tool (FAST)	Change in functional status as assessed by FAST using a points system	3 weeks from baseline examination
Change in functional status as assessed by Patient-Specific Functional Scale (PSFS)	Change in functional status as assessed by PSFS using a points system	3 weeks from baseline examination
Change in functional status as assessed by Knee injury and Osteoarthritis Outcome Score (KOOS)	Change in functional status as assessed by KOOS using a points system	3 weeks from baseline examination
Patients' self-perception of change in their knee condition as assessed by Global Rating of Change Score (GROC)	Patients' self-perception of change in their knee condition as assessed by GROC using a points system	3 weeks from baseline examination

Collaborators and Investigators

• Sponsor: SingHealth Polyclinics
• Collaborators: Singapore Institute of Technology
• Investigators: Principal Investigator: Zhi Yin Tang, SingHealth Polyclinics

Publications and helpful links

General Publications

• Chatman AB, Hyams SP, Neel JM, Binkley JM, Stratford PW, Schomberg A, Stabler M. The Patient-Specific Functional Scale: measurement properties in patients with knee dysfunction. Phys Ther. 1997 Aug;77(8):820-9. doi: 10.1093/ptj/77.8.820.
• Stratford P, Gill C, Westaway M, Binkley J. Assessing disability and change on individual patients: a report of a patient specific measure. Physiotherapy Canada. 1995;47(4):258-63.
• Xie F, Li SC, Roos EM, Fong KY, Lo NN, Yeo SJ, Yang KY, Yeo W, Chong HC, Thumboo J. Cross-cultural adaptation and validation of Singapore English and Chinese versions of the Knee injury and Osteoarthritis Outcome Score (KOOS) in Asians with knee osteoarthritis in Singapore. Osteoarthritis Cartilage. 2006 Nov;14(11):1098-103. doi: 10.1016/j.joca.2006.05.005. Epub 2006 Jun 30.

Study record dates

Study Major Dates

• Study Start (Actual): February 13, 2023
• Primary Completion (Actual): September 15, 2023
• Study Completion (Actual): September 15, 2023

Study Registration Dates

• First Submitted: October 18, 2022
• First Submitted That Met QC Criteria: October 20, 2022
• First Posted (Actual): October 21, 2022

Study Record Updates

• Last Update Posted (Actual): June 26, 2025
• Last Update Submitted That Met QC Criteria: June 23, 2025
• Last Verified: June 1, 2025

More Information

Terms related to this study

• Keywords: Knee injury and Osteoarthritis Outcome Score; Functional assessment; Patient-Specific Functional Scale; Functional Activity Scoring Tool
• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Arthritis; Joint Diseases; Rheumatic Diseases; Osteoarthritis; Osteoarthritis, Knee
• Other Study ID Numbers: 202206-00049

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

IPD Plan Description

De-identified individual participant data (IPD) that will be shared include:

• Demographics data
• Outcome data for primary and secondary endpoints

• IPD Sharing Time Frame: IPD will be available beginning 6 months after publication of the primary results and will remain available for 5 years thereafter.
• IPD Sharing Access Criteria: Data will be made available to qualified researchers upon reasonable request, subject to approval by the sponsor and completion of a data use agreement.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No