Formative Evaluation of a Mobile Application Facilitated Self-directed Rehabilitation Programme for Knee Osteoarthritis

The feasibility of evaluating the prototype in a larger trial will be assessed using predefined progression criteria including, including recruitment and retention rates, adherence to the program, incidence of adverse events, and improvement in function. Progression will be guided using thresholds categorized as "proceed," "proceed with protocol amendments," or "significant amendments required" based on the criteria defined for each feasibility domain.

Gait speed will be measured from walking a distance of 4m at comfortable pace and 9m at fast pace with a 2m acceleration and deceleration zone before and after the timed section of 9m.

A long-arm goniometer will be used to measure active-assisted knee flexion and extension range-of-motion with the participants in supine position

This is a tool developed to measure physical activity, distinguishing between incidental exercise (activities that are not planned but contribute to overall physical activity, like walking to work or taking the stairs) and planned exercise (deliberate, structured exercise like going to the gym or running)

The EQ5D-5L is a standardised instrument to measure health related quality of life in cost-effectiveness analysis

Isotonic quadriceps strength will be determined using the one-repetition maximum test, which is the maximum load the patient could lift once in good form. A submaximal warm-up was provided by instructing the patient to perform bilateral knee extension at < 10 kgs. The range of-motion for the test was set from 90° to 40° of knee flexion to avoid the increased patellofemoral joint stress associated with terminal knee extension

Participants' grip strength will be measured using Jamar hand dynamometer

This assesses the ability of the participants to weight bear on their limb. With their feet on 2 portable force plates, participants will stand up from a standard chair, and weight-bearing symmetry is calculated by expressing the peak force produced by the operated leg as a percentage of that produced by the unoperated leg.

A test to assess participants' ability to rise from a chair and return to the sitting position. The time taken for participant to stan up and sit down five times as fast as posible from standard chair (43-47cm) without the use of their hands will be recorded. This test is a measure that is performed as part of standard clinical practice and is also a measure of lower limb strength and dynamic balance.

Participants will report their physical function using the Short Modified Arthritis Measure for Function (Short-MAC-F), which assesses difficulty in performing common daily activities related to knee function, including stair negotiation, rising from sitting, walking on a flat surface, getting in and out of a car, and dressing. Each item is rated on a 5-point Likert scale, where 0 indicates "none" and 4 indicates "extreme" difficulty. Higher scores indicate greater functional limitation.

Participants will rate their satisfaction with the rehabilitation programme using the prototype on a 11 point Likert scale, with 0 indicating "no satisfaction" and 10 indicating "complete satisfaction".

Self-reported compliance will be collected by asking participants how many times they completed their exercises. Compliance will also be determined from the data logs captured by the mobile application.

Participants will report their fear of movement related to knee osteoarthritis using the Brief Fear of Movement Scale (BFOM). The scale consists of multiple statements assessing beliefs about movement, injury, and pain. Each item is rated on a 4-point Likert scale, where 1 indicates "strongly disagree" and 4 indicates "strongly agree."

Four-dimensional symptom questionnaire (4DSQ) will be used to assess psychological distress, anxiety, depression and

Participants will rate how necessary they perceive knee replacement surgery for their condition based on knee symptoms over the past week using an 11-point numeric rating scale from 0 to 10 (allowing increments of 0.5), where 0 indicates "not at all necessary" and 10 indicates "totally necessary." Participants will also provide a categorical rating of perceived necessity, ranging from "not at all necessary" to "totally necessary." Higher scores indicate a greater perceived need for knee replacement surgery.

Participants will rate their knee pain intensity during specific activities using a Visual Analogue Scale (VAS), ranging from 0 to 10, where 0 indicates "no pain" and 11 indicates "worst imaginable pain." Higher scores indicate greater pain intensity.

Participants will attend an exit interview session at study completion to evaluate their experiences and perceptions of using the mobile application and force platforms for self-directed rehabilitation.

Qualitative data will be collected through guided interviews, recorded, and analyzed thematically to assess usability, acceptability, and user experience. Findings from these interviews will be used to inform refinements to optimize the application design and overall user experience.

Participants will provide an overall rating of their knee condition using a global rating scale reflecting their perception of their knee and associated problems. Higher scores indicate greater perceived severity of impairment.

Participants will report their highest level of education attained, categorized into predefined levels (e.g., primary, secondary, tertiary).

Race will be self-reported by participants and categorized into predefined groups (e.g., Chinese, Malay, Indian, Others) based on standard demographic classifications.

Co-morbidities will be recorded based on participant self-report and/or medical records, including the presence of chronic conditions such as hypertension, diabetes, cardiovascular disease, and others.

Severity of knee osteoarthritis will be assessed using the Kellgren-Lawrence (K-L) grading scale based on radiographic findings, with grades ranging from 0 (no radiographic features of osteoarthritis) to 4 (severe osteoarthritis).

Height (in centimeters) will be measured or self-reported and used to calculate body mass index (BMI) in kg/m².

Weight (in kilograms) will be measured or self-reported and used to calculate body mass index (BMI) in kg/m².

Gender will be self-reported by participants and categorized as male or female

Participants will report their confidence and frequency of using technology in daily life. Confidence in using technology will be assessed using a 4-point scale, where 0 indicates "not at all confident" and 3 indicates "extremely confident," with higher scores indicating greater confidence.

Frequency of technology use will be assessed across a range of common digital tools (e.g., mobile phone, SMS, computer, email, tablet, video conferencing platforms, online shopping, internet use, and social media). Each item will be rated on a 6-point scale ranging from "never" to "every day," with higher scores indicating more frequent use of technology.

Knowledge of knee osteoarthritis will be assessed using the Knee Osteoarthritis Knowledge Scale, with higher scores indicating greater understanding of the condition, its management, and treatment options.

Participants will rate their agreement with statements assessing their ability to find and use online health information using a 5-point Likert scale, where 1 indicates "strongly disagree" and 5 indicates "strongly agree." Higher scores indicate greater perceived eHealth literacy.

Participants will rate their perceived social support from family using the Multidimensional Scale of Perceived Social Support (MSPSS). Items are rated on a 7-point Likert scale, where 1 indicates "very strongly disagree" and 7 indicates "very strongly agree." The scale assesses perceived emotional and practical support from family, including help with decision-making, availability of support, and ability to discuss problems. Higher scores indicate greater perceived social support.