Knee OsteoarthritisEXPLORNCT07901881
The Effect of Theory-driven Physiotherapy on Physical Activity in Knee OA.
A study testing EXPLOR-3 in people with Knee Osteoarthritis, run by Mark van Loo at 1 site in Netherlands.
Trial summary
Knee osteoarthritis (OA) is a leading cause of pain, disability, and reduced physical functioning worldwide. Although physiotherapy and physical activity are recommended as first-line treatments, many individuals with knee OA do not achieve or maintain recommended levels of physical activity. Read more about this study
- Who is it for?
- Ages 45 to 70 years
- Conditions the study is for
- Knee Osteoarthritis
- What is being tested?
- EXPLOR-3
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 20 participants
- Where
- 1 siteNetherlands
- Study dates
- 30 Oct 2026to 1 Jan 2028
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 45 to 70 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 45-70 years of age,
- knee osteoarthritis in accordance with the National Institute for Health and Care Excellence (NICE) guideline: people who i) have activity related joint pain and ii) have no or brief (≤ 30 min.) morning stiffness of the affected joint
- there is an indication for guided exercise therapy (treatment indication 2 or 3 from the Osteoarthritis guideline of the Royal Dutch Society for Physical Therapy) and
- are able to read and understand Dutch.
Who cannot join
- already performs ≥150 minutes of moderate physical activity per week,
- rheumatoid arthritis,
- known cardiovascular disease,
- known neurological or psychiatric disorder,
- recent surgery (within the last 3 months) of the affected joint,
- having had joint replacement surgery (at the side of the current pain problem).
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Netherlands1 site
Rotterdam University of Applied Science
Rotterdam, 3015EK
Mark van Loo, MSc., +31643280339, m.k.van.loo@hr.nl
About this study
Official title: What is the Effect of Theory-driven Physiotherapy on Physical Activity in People With Knee Osteoarthritis: A Multiple Baseline Single-case Experimental Design Study.
Knee osteoarthritis (OA) is a leading cause of pain, disability, and reduced physical functioning worldwide. Although physiotherapy and physical activity are recommended as first-line treatments, many individuals with knee OA do not achieve or maintain recommended levels of physical activity. As a result, the benefits of evidence-based physiotherapy are often not fully realized. To improve physical activity participation, effective behaviour change interventions are needed.
Theory-informed interventions have the potential to enhance physiotherapy outcomes by targeting the psychological determinants that influence physical activity behaviour. One well-established framework is the Theory of Planned Behaviour (TPB), which proposes that behaviour is primarily influenced by behavioural intention, attitude, subjective norms, and perceived behavioural control. To translate these determinants into intervention content, behaviour change techniques (BCTs) can be systematically selected using tools such as the Behaviour Change Intervention Ontology (BCIO), Mechanisms of Action Ontology (MoAO), and Theory and Techniques Tool (TaTT). This approach may improve the effectiveness and sustainability of behaviour change interventions.
Read more
The present study therefore aims to evaluate the potential of a TPB-based behaviour change intervention as an addition to guideline-recommended physiotherapy for individuals with knee OA. The primary objective is to determine whether this theory-driven intervention can improve physical activity levels and reduce sedentary behaviour. A secondary objective is to explore the behavioural mechanisms through which these changes occur.
The study will employ a randomized, concurrent, multiple-baseline single-case experimental design (SCED). Participants with knee OA will receive a six-week physiotherapy intervention consisting of usual guideline-based care supplemented with a TPB-based behaviour change component. Physical activity and sedentary behaviour will be continuously assessed using ActiGraph accelerometers. In addition, behavioural determinants, pain, and functional limitations will be repeatedly measured to evaluate potential mechanisms of action and clinical effects. Findings from this study may contribute to the development of more effective, theory-informed physiotherapy interventions aimed at promoting sustainable physical activity behaviour in people with knee OA.
- Conditions
- Knee Osteoarthritis
- Being tested
- EXPLOR-3
- Keywords
- Physiotherapy, Single Case, Physical activity, Theory of Planned Behaviour, Behaviour Change
- Medical subject headings
- Osteoarthritis, Knee, Motor Activity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
EXPLOR-3Behavioural
Also called Guideline care complementary behaviour change intervention
The behaviour change component will be developed based on the TPB. Selection of corresponding MoAs and BCTs will be guided by the BCIO, the MoA Ontology, and the TaTT. Within the TPB framework, three MoAs are known to predict intention and actual behavior.
Accordingly, the intervention applies a stepwise, phased approach when implementing TPB within a physiotherapy context aimed at increasing physical activity (≥150 minutes of moderate physical activity per week). The intervention first targets individuals' attitudes toward the behavior (treatment phase 1, duration 1-2 weeks), followed by enhancement of perceived behavioral control (treatment phase 2, duration 2-3 weeks), and subsequently aims to strengthen behavioral intention (treatment phase 3, duration 2 weeks). For each phase, specific BCTs will be selected to align with the corresponding MoAs (based on link within TaTT) and will be tailored to individual patient needs, as assessed by the physical therapist.
| Study group | Role | What they receive |
|---|---|---|
| Multiple baseline phase (Phase A) | No intervention | Multiple baseline phase. Participants will complete repeated measures during this phase. The duration of this phase will be randomized to 7, 10 or 14 days. Participant will not receive treatment during this phase. The measurements from this phase will be used a control to the data that will be collected within the treatment phase (Phase B). |
| Intervention Phase (Phase B): Guideline care complementary behaviour change intervention | Experimental | The intervention will consist of the guideline-recommended treatment protocol, supplemented with a behaviour change component designed to enhance treatment effectiveness by targeting key determinants of behaviour change. The behaviour change component is intended to complement, rather than replace, the standard treatment. In accordance with usual clinical practice, the content and delivery of the guideline-based treatment will be tailored to the individual needs, goals, and clinical presentation of each participant. Tailoring of the treatment will be performed by the treating physical therapist. Receives: Behavioral: EXPLOR-3 |
| Follow-up (Phase A') | No intervention | Follow-up period of three months takes place after phase B. Participant will not receive treatment during this period. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in physical activity (ActiGraph GT3x) from Phase A to Phase B to Phase A'.
Physical activity will be assessed using ActiGraph GT3x (ActiGraph, Pensacola, Florida) triaxial accelerometers. Participants will be instructed to wear the accelerometer on their thigh while they are awake during the A and B phase and the last 5 days of the A' phase. Physical activity thresholds will be used to distinguish between sedentary behaviour and light, moderate and vigorous physical activity.
Measured: Daily measurements for 7-8 weeks (A+B Phase) and the last 5 days of the follow-up phase (Phase A'). Duration of follow-up phase is 12 weeks.
Change in sedentary behaviour (ActiGraph GT3x) from Phase A to Phase B to Phase A'.
Sedentary behaviour will be assessed using ActiGraph GT3x (ActiGraph, Pensacola, Florida) triaxial accelerometers. Participants will be instructed to wear the accelerometer on their thigh while they are awake during the A and B phase and the last 5 days of the A' phase. Physical activity thresholds will be used to distinguish between sedentary behaviour and light, moderate and vigorous physical activity.
Measured: Daily measurements for 7-8 weeks (A+B Phase) and the last 5 days of the follow-up phase (Phase A'). Duration of follow-up phase is 12 weeks.
Secondary outcomes (3)
Change on the Knee Injury and Osteoarthritis Outcome Score from phase A to phase B to follow-up.
The Knee Injury and Osteoarthritis Outcome Score (KOOS) comprises five subscales: 1) Pain (9 items), 2) Symptoms (7), 3) Activities of Daily Living (17), 4) Sport/Rec (5), and 5) knee related Quality of Life (4). Questions are scored 0-100 (worst-best). Internal consistency is adequate (pooled Cronbach's α≈0.70-0.95) and test-retest reliability high (ICCs ≈0.85-0.90). Content validity is condition and age sensitive: ADL is more relevant in older OA cohorts and Pain in painful conditions.
Measured: At start of baseline, after 3 weeks and 6 weeks of treatment and at the end of the follow-up phase. Follow-up phase is 12 weeks.
Change on the Patient Specific Functional Scale (PFPS) from phase A to phase B to follow-up.
The PSFS is a patient reported, individualized measure in which patients nominate two activities and rate difficulty on an 11 point scale (0-10); higher scores reflect better function. Test-retest reliability across musculoskeletal conditions (e.g., ICC ≈0.82-0.97) is reported good to excellent. Construct/concurrent validity is supported via correlations with the RMQ, NDI, and SF 36, and predictive validity for return to work outcomes.
Measured: At start of baseline, after 3 weeks and 6 weeks of treatment and the end of the follow-up phase. Follow-up phase is 12 weeks.
Change on the Numeric Pain Rating Scale (NPRS) from phase A to phase B to follow-up.
The NPRS is a unidimensional self report of pain intensity, typically using 0-10 anchors ("no pain" to "pain as bad as you can imagine"). Scores generally correspond to VAS, though not perfectly interchangeable. The NPRS is widely used in pain research and its psychometric characteristics are reported to be good.
Measured: At start of baseline, after 3 weeks and 6 weeks of treatment and at the end of the follow-up phase. Follow-up phase is 12 weeks.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted28 Oct 2026
- Study start30 Oct 2026 (estimated)
- Primary completion1 Dec 2027 (estimated)
- Study completion1 Jan 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Knee OsteoarthritisStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- A randomized, concurrent, multiple baseline single-case design will be applied. Participants will complete repeated measures during a baseline phase (phase A), an intervention period (phase B), and a follow-up period (phase A') Phase A will act as a control and will therefore be compared with phases B and A'. Baseline phase will last 7, 10 or 14 days. Data collection during baseline will be concurrent between participants. Treatment onset will be based on baseline duration. The intervention period will last 6 weeks. The follow-up period will last 3 months.
- Masking
- None (open label)
- Enrolment
- 20 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Mark van Loo
- Sponsor type
- University, hospital or other
- Collaborators
- Vrije Universiteit Brussel, Erasmus Medical Center, Hogeschool Leiden, University of Applied Science
- Responsible party
- Sponsor-investigator, Mark van Loo, Rotterdam University of Applied Sciences
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07901881
- Sponsor's protocol ID
- EXPLOR-3
- Other IDs
- 20221002
- Acronym
- EXPLOR
- Status last verified
- Oct 2026
- First submitted
- 12 Oct 2026
- Last updated
- 28 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 28 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- What is the Effect of Theory-driven Physiotherapy on Physical Activity in People With Knee Osteoarthritis: A Multiple Baseline Single-case Experimental Design Study.
- ClinicalTrials.gov ID
- NCT07901881
- Acronym / sponsor ID
- EXPLOR / EXPLOR-3
- Conditions
- Knee Osteoarthritis
- Keywords
- Physiotherapy, Single Case, Physical activity, Theory of Planned Behaviour, Behaviour Change
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 20 participants (estimated)
- Lead sponsor
- Mark van LooUniversity, hospital or other
- Collaborators
- Vrije Universiteit Brussel, Erasmus Medical Center, Hogeschool Leiden, University of Applied Science
- Study start
- 30 Oct 2026 (estimated)
- Primary completion
- 1 Dec 2027 (estimated)
- Study completion
- 1 Jan 2028 (estimated)
- First posted
- 28 Oct 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Knee osteoarthritis (OA) is a leading cause of pain, disability, and reduced physical functioning worldwide. Although physiotherapy and physical activity are recommended as first-line treatments, many individuals with knee OA do not achieve or maintain recommended levels of physical activity. As a result, the benefits of evidence-based physiotherapy are often not fully realized. To improve physical activity participation, effective behaviour change interventions are needed.
Theory-informed interventions have the potential to enhance physiotherapy outcomes by targeting the psychological determinants that influence physical activity behaviour. One well-established framework is the Theory of Planned Behaviour (TPB), which proposes that behaviour is primarily influenced by behavioural intention, attitude, subjective norms, and perceived behavioural control. To translate these determinants into intervention content, behaviour change techniques (BCTs) can be systematically selected using tools such as the Behaviour Change Intervention Ontology (BCIO), Mechanisms of Action Ontology (MoAO), and Theory and Techniques Tool (TaTT). This approach may improve the effectiveness and sustainability of behaviour change interventions.
The present study therefore aims to evaluate the potential of a TPB-based behaviour change intervention as an addition to guideline-recommended physiotherapy for individuals with knee OA. The primary objective is to determine whether this theory-driven intervention can improve physical activity levels and reduce sedentary behaviour. A secondary objective is to explore the behavioural mechanisms through which these changes occur.
The study will employ a randomized, concurrent, multiple-baseline single-case experimental design (SCED). Participants with knee OA will receive a six-week physiotherapy intervention consisting of usual guideline-based care supplemented with a TPB-based behaviour change component. Physical activity and sedentary behaviour will be continuously assessed using ActiGraph accelerometers. In addition, behavioural determinants, pain, and functional limitations will be repeatedly measured to evaluate potential mechanisms of action and clinical effects. Findings from this study may contribute to the development of more effective, theory-informed physiotherapy interventions aimed at promoting sustainable physical activity behaviour in people with knee OA.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 3
- Model description
- A randomized, concurrent, multiple baseline single-case design will be applied. Participants will complete repeated measures during a baseline phase (phase A), an intervention period (phase B), and a follow-up period (phase A') Phase A will act as a control and will therefore be compared with phases B and A'. Baseline phase will last 7, 10 or 14 days. Data collection during baseline will be concurrent between participants. Treatment onset will be based on baseline duration. The intervention period will last 6 weeks. The follow-up period will last 3 months.
| Arm | Type | Receives |
|---|---|---|
| Multiple baseline phase (Phase A) | No intervention | –Multiple baseline phase. Participants will complete repeated measures during this phase. The duration of this phase will be randomized to 7, 10 or 14 days. Participant will not receive treatment during this phase. The measurements from this phase will be used a control to the data that will be collected within the treatment phase (Phase B). |
| Intervention Phase (Phase B): Guideline care complementary behaviour change intervention | Experimental | Behavioral: EXPLOR-3The intervention will consist of the guideline-recommended treatment protocol, supplemented with a behaviour change component designed to enhance treatment effectiveness by targeting key determinants of behaviour change. The behaviour change component is intended to complement, rather than replace, the standard treatment. In accordance with usual clinical practice, the content and delivery of the guideline-based treatment will be tailored to the individual needs, goals, and clinical presentation of each participant. Tailoring of the treatment will be performed by the treating physical therapist. |
| Follow-up (Phase A') | No intervention | –Follow-up period of three months takes place after phase B. Participant will not receive treatment during this period. |
Who may qualify
- Ages
- 45 to 70 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- 45-70 years of age,
- knee osteoarthritis in accordance with the National Institute for Health and Care Excellence (NICE) guideline: people who i) have activity related joint pain and ii) have no or brief (≤ 30 min.) morning stiffness of the affected joint
- there is an indication for guided exercise therapy (treatment indication 2 or 3 from the Osteoarthritis guideline of the Royal Dutch Society for Physical Therapy) and
- are able to read and understand Dutch.
Key exclusion criteria (6 listed)
- already performs ≥150 minutes of moderate physical activity per week,
- rheumatoid arthritis,
- known cardiovascular disease,
- known neurological or psychiatric disorder,
- recent surgery (within the last 3 months) of the affected joint,
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| EXPLOR-3Also: Guideline care complementary behaviour change interventionThe behaviour change component will be developed based on the TPB. Selection of corresponding MoAs and BCTs will be guided by the BCIO, the MoA Ontology, and the TaTT. Within the TPB framework, three MoAs are known to predict intention and actual behavior. Accordingly, the intervention applies a stepwise, phased approach when implementing TPB within a physiotherapy context aimed at increasing physical activity (≥150 minutes of moderate physical activity per week). The intervention first targets individuals' attitudes toward the behavior (treatment phase 1, duration 1-2 weeks), followed by enhancement of perceived behavioral control (treatment phase 2, duration 2-3 weeks), and subsequently aims to strengthen behavioral intention (treatment phase 3, duration 2 weeks). For each phase, specific BCTs will be selected to align with the corresponding MoAs (based on link within TaTT) and will be tailored to individual patient needs, as assessed by the physical therapist. | Behavioural | Intervention Phase (Phase B): Guideline care complementary behaviour change intervention |
Primary outcome
Change in physical activity (ActiGraph GT3x) from Phase A to Phase B to Phase A'.
Time frame: Daily measurements for 7-8 weeks (A+B Phase) and the last 5 days of the follow-up phase (Phase A'). Duration of follow-up phase is 12 weeks.
Physical activity will be assessed using ActiGraph GT3x (ActiGraph, Pensacola, Florida) triaxial accelerometers. Participants will be instructed to wear the accelerometer on their thigh while they are awake during the A and B phase and the last 5 days of the A' phase. Physical activity thresholds will be used to distinguish between sedentary behaviour and light, moderate and vigorous physical activity.
Change in sedentary behaviour (ActiGraph GT3x) from Phase A to Phase B to Phase A'.
Time frame: Daily measurements for 7-8 weeks (A+B Phase) and the last 5 days of the follow-up phase (Phase A'). Duration of follow-up phase is 12 weeks.
Sedentary behaviour will be assessed using ActiGraph GT3x (ActiGraph, Pensacola, Florida) triaxial accelerometers. Participants will be instructed to wear the accelerometer on their thigh while they are awake during the A and B phase and the last 5 days of the A' phase. Physical activity thresholds will be used to distinguish between sedentary behaviour and light, moderate and vigorous physical activity.
3 secondary outcomes
Change on the Knee Injury and Osteoarthritis Outcome Score from phase A to phase B to follow-up.
Time frame: At start of baseline, after 3 weeks and 6 weeks of treatment and at the end of the follow-up phase. Follow-up phase is 12 weeks.
Change on the Patient Specific Functional Scale (PFPS) from phase A to phase B to follow-up.
Time frame: At start of baseline, after 3 weeks and 6 weeks of treatment and the end of the follow-up phase. Follow-up phase is 12 weeks.
Change on the Numeric Pain Rating Scale (NPRS) from phase A to phase B to follow-up.
Time frame: At start of baseline, after 3 weeks and 6 weeks of treatment and at the end of the follow-up phase. Follow-up phase is 12 weeks.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 28 Oct 2026.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing EXPLOR-3 in people with Knee Osteoarthritis, run by Mark van Loo at 1 site in Netherlands.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 6 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 28 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Netherlands. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Mark van Loo, MSc. (+31643280339, m.k.van.loo@hr.nl), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in physical activity (ActiGraph GT3x) from Phase A to Phase B to Phase A'. (time frame: Daily measurements for 7-8 weeks (A+B Phase) and the last 5 days of the follow-up phase (Phase A'). Duration of follow-up phase is 12 weeks.). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 28 Oct 2026.