Table 3 Outcome measures

1. Sociodemographic and clinical data

  Sociodemographic data

Data of the participants’ age, gender, ethnicity, education level, housing type, marital status, living arrangement, occupation will be collected through self-report

  Arthritis status

Clinical variables including arthritis profile, duration, mobility and radiographic severity (Kellegren-Lawrence), and will be collected through a combination of self-report and clinical data extraction

  Comorbidity and Functional Status

Charlson comorbidity index [27], Barthel Index for Activities of Daily Living [28] and Parker Mobility Score [29]

2. Knee function

  KOOS-12

KOOS-12 is a 12-item assessment tool on the participants’ perception of their knee function in the domains of pain, function and daily living, and quality of life [36]. It is measured on a 5-point Likert scale from 0 to 4, with 4 questions in each domain and scored using summative scores in each domain

  Physical Performance

4 physical performance activities encompass the key domains of functional activities

1. Gait speed

2. Timed up-and-go

3. 4-stair climb test

4. 30-s chair stand

3. Quality of life

The EQ-5D-5L questionnaire, consisting of 5 domains (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression) will be used to assess participant’s quality of life [43]. Each dimension contains 5 levels, from no problem to extreme problems. A 5-digit number which describes the patient’s health state will be generated based on the levels that participants selected for each item. A subsequent index can be computed based on the valuation of the number. A vertical visual analogue scale in the assessment tool also provides for a quantitative measure of participants’ perceived health status

4. Depression and anxiety

The Patient Health Questionnaire-4 (PHQ-4) is a 4-item questionnaire answered on a four-point Likert-scale to allow the measurement of core sign and symptoms of depression and anxiety [14]. Total score is determined by adding together the scores of each of the 4 items. Scores are rated as normal (0–2), mild (3–5), moderate (6–8), and severe (9–12)

5. Pain experience

Pain average (P), interference with Enjoyment of life (E), and interference with General activity (G) (PEG) will be used to assess the pain experience [44]. The PEG is a three-item measure derived from the Brief Pain Inventory (BPI) [11, 45] that measures average pain intensity (one item) and pain interference (two items). Patients rate their pain intensity on a numerical rating scale from 0 (no pain) to 10 (pain as bad as you can imagine) and pain interference with enjoyment of life and general activity from 0 (does not interfere) to 10 (completely interferes). A mean score from the three questions will be computed to derive the overall pain impact

6. Activity level

The UCLA activity score is a 10-point activity scale that assesses activity level based on 10 descriptive activity levels ranging from 1 (i.e., wholly inactive, dependent on others and cannot leave residence) to 10 (i.e., regular participation in impact sports) [38]

7. Dietary behaviours

A dietary related questionnaire will be used to survey the dietary habits of the participants over the past four months. Questions include the frequency of intake of deep-fried foods, fruits and vegetables, whole grains, and sugar, as well as frequency of over-eating, stress eating, and dietary intention. Responses are reviewed and domain scores will be derived where applicable

8. Global and satisfaction

  Global Assessment

The Global Perceived Effect (GPE) scale assesses the patient’s perception of knee OA progression [46]. It is a single item measure with 7-point Likert scale

  Satisfaction with treatment

Patient Acceptable Symptom Scale (PASS) consists of an item pertaining to the perceived satisfaction of knee function, with a binary yes/no response [47]

  Treatment failure

Perceived treatment failure will be assessed by an item about the participant’s current condition relating to the failure of the current course of treatment, with a binary yes/no response

9. Perceived quality of care

The OA Quality Indicator (OA-QI) questionnaire seeks to understand the self-reported standard and level of information that the patient was provided with by the healthcare organisation [48]

10. Costs

Data on the acute health services usage (surgical, medication, others), specialist/medical service usage, community services programme, aids and adaptation will be collected, and the cost on the services related to the knee will be retrieved from the hospital data and the patient-reported cost questionnaire based on the Work Productivity and Activity Impairment Questionnaire (WPAI) and OA Cost and Consequences Questionnaire (OCC-Q)

11. Psychosocial

  Fear of movement

Brief Fear of Movement (BFOM) assesses the fear of movement that patient experience [49]. The questionnaire consists of six questions with a 4-point Likert scale ranging from 1 (strongly disagree) to 4 (strongly agree). A summative score of the six questions will be computed, with higher score indicating greater fear of movement

  Self-efficacy

The Arthritis Self-Efficacy Scale (ASES) assesses how the participants’ confidence in performing certain daily tasks [50]. The summative score indicates the level of self-efficacy the participant has in managing their arthritis

  Pain acceptance

Chronic Pain Acceptance Questionnaire – 2 (CPAQ-2) is a two-item questionnaire that explores participants’ acceptance of pain in their daily living [51]. Participants rate their response in a seven-point Likert scale range from never true (1) to always true (7)

  Injustice experience

The Injustice Experience Questionnaire consists of 12 statements that assesses how participants’ perception of injustice in their health condition [52]. The responses will be recorded in a five-point Likert scale range from 0—not at all to 4—all the time, and a total score of all the questions will be computed

  Social support

The Multidimensional Scale of Perceived Social Support (MSPSS) is used to measure patients’ perception of perceived social support [53]. There were 12 questions in the questionnaire, and each item is rated on a seven-point Likert-type response format (1—very strongly disagree; 7—very strongly agree). A total score is calculated by summing the results for all items. The possible score range is between 12 and 84, the higher the score the higher the perceived social support

  Chronic illness-related shame 

Chronic illness-related shame score (CISS) is a scale specifically focused on shame feelings derived from illness-related experiences [54]. The CISS composed of seven items measured on a five-point Likert scare range from 0 (Never True) to 4 (Always True)

  Religion and spirituality

The religion and spirituality questionnaire is a 2-item assessment tool developed by the study team to assess the extent that religion and spirituality is a factor in helping the patient cope with their knee condition. The items are rated from 1 (very strongly agree) to 7 (very strongly disagree)

  Built environment

The built environment questionnaire is a 5-item developed by the study team to assess the participant’s perceptions of accessibility of physical facilities and amenities around their place of residence. This was adapted from the International Physical Activity Questionnaire (IPAQ) environmental module [55]. The items are rated from 1 (very strongly agree) to 7 (very strongly disagree)