Knee OsteoarthritisP4ACENCT05623683
P4ACE Trial for Persons With Chronic Knee Pain
A study testing Intermittent Walking and Continuous Walking in people with Knee Osteoarthritis, run by Northwestern University at 1 site in Denmark.
Trial summary
The goal of this single-blind, cross-over clinical trial is to compare the immediate effect of intermittent vs. continuous walking on clinical and mechanistic pain profiles in persons with knee osteoarthritis (OA). In this cross-over trial, participants will perform two types of walking on a treadmill. Read more about this study
- Who is it for?
- Ages 45 to 75 years
- Conditions the study is for
- Knee Osteoarthritis
- What is being tested?
- Intermittent Walking and Continuous Walking
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 23 participants
- Where
- 1 siteDenmark
- Study dates
- 20 Apr 2023to 31 Jul 2024
- Phase
- Interventional
- Are there results?
- None posted in the registry
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 75 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- men or women aged 45-75 years
- BMI ≤ 35 kg/m2
- frequent movement-related knee pain (knee pain on more than half the days of the past month)
- no morning stiffness or morning stiffness lasting < 30-min
- self-reported unilateral or bilateral knee pain of ≥ 3 and ≤ 7 on a 0-10 numeric pain rating scale (NPRS)
- knee pain duration ≥ 12 months
Show all 9Show fewer
- physically able to walk unassisted on a treadmill at ≥ 4 km/hour for 30 minutes
- own a smart phone
- willing and able to wear an activity monitor and answer electronic survey questions delivered via a smart phone over a 10-day period.
Who cannot join
- intra-articular steroid injections in the previous 3 months
- intra-articular hyaluronic acid injection in the previous 6 months
- any arthroscopic or surgical knee procedures (e.g., partial meniscectomy) in the past 12 months
- lumbar radiculopathy
- neurological, vestibular, or visual dysfunction affecting walking balance and mobility
- plan for total knee arthroplasty in the next 12 months
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Pain Profiles and Patterns of Physical Activity in Persons With Chronic Knee Pain
The goal of this single-blind, cross-over clinical trial is to compare the immediate effect of intermittent vs. continuous walking on clinical and mechanistic pain profiles in persons with knee osteoarthritis (OA). In this cross-over trial, participants will perform two types of walking on a treadmill. Intermittent walking will involve 3 blocks of 10 minutes with 2 blocks of 5-minute rest (sitting on a chair) in-between. Continuous walking will involve resting for 10 minutes (sitting in a chair) before walking on the treadmill for 1 continuous block of 30 minutes.
Read the detailed description
The study objectives are to compare the immediate effect of intermittent vs. continuous walking on clinical and mechanistic pain profiles in persons with knee osteoarthritis (OA). The investigators hypothesize that continuous walking will result in greater increases in clinical pain and mechanistic pain sensitivity than intermittent walking. Physical activity (PA) has been recommended as the first-line management strategy for people with chronic knee pain. Walking is an accessible, low-cost, joint-friendly form of PA and is widely advocated for older adults with knee complaints. However, movement-evoked pain is a commonly cited barrier for PA engagement. On one hand, a bout of PA may produce short-term analgesia and reduce pain. On the other hand, excessive or prolonged PA may exacerbate symptoms and lead to avoidance/fear of subsequent PA. Besides the total PA volume, how it is accumulated could also impact joint health. It is biomechanically plausible that shorter and frequent activities are more beneficial to articular tissues than longer and infrequent activities. Compared to intermittent loading, prolonged continuous loading had a detrimental effect on the biomechanical functions of articular cartilage in a bovine model. Findings of this study will provide insight on the relations between patterns of PA and pain profiles.
- Conditions
- Knee Osteoarthritis
- Being tested
- Intermittent Walking, Continuous Walking
- Medical subject headings
- Osteoarthritis, Knee
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Intermittent WalkingOther
Wearing comfortable clothes and their usual walking shoes, participants will walk on a treadmill to accrue 30 minutes of walking. Participants will be instructed not to use the treadmill side rails for balance or support during walking. Participants will walk on the treadmill for 3 blocks of 10 minutes with 2 blocks of 5-minute rest (sitting on a chair) in-between. A safety button to stop the treadmill will be available to the participants, so they can stop walking anytime. If participants feel that they are about to lose balance, they are allowed to hold on to the side rails to regain balance and terminate the trial.
Continuous WalkingOther
Wearing comfortable clothes and their usual walking shoes, participants will walk on a treadmill to accrue 30 minutes of walking. Participants will be instructed not to use the treadmill side rails for balance or support during walking. Participants will rest for 10 minutes (sitting in a chair) before walking on the treadmill for 1 continuous block of 30 minutes. A safety button to stop the treadmill will be available to the participants, so they can stop walking anytime. If participants feel that they are about to lose balance, they are allowed to hold on to the side rails to regain balance and terminate the trial.
| Study group | Role | What they receive |
|---|---|---|
| Intermittent Walking | Active comparator | Intermittent walking on the treadmill Receives: Other: Intermittent Walking |
| Continuous Walking | Active comparator | Continuous walking on the treadmill Receives: Other: Continuous Walking |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change from pre-walking to immediately post-walking in Numeric Pain Rating Scale (NPRS) for current knee pain
The primary outcome is the self-reported clinical pain. The pre- and post-walking knee pain will be rated right before the commencement of the walking program and at the termination of the walking program respectively. Participants verbally select a value that corresponds with the intensity of pain that they experience. "0" means "no pain" and "10" means "pain as bad as you can imagine" or "worst pain imaginable". The NPRS, an 11-point (i.e., 0-10) measure of pain intensity, is recommended as a core outcome measure in clinical trials of chronic pain treatments and has excellent reliability and validity for adults with chronic musculoskeletal pain. On average, a change of 2 points or a change of approximately 30% in NPRS represented a clinically important difference in adults with chronic pain.
Measured: pre-walking, immediately post-walking
Secondary outcomes (4)
Change from pre-walking to immediately post-walking in Cuff Pain Detection Threshold (cPDT)
A computer-controlled cuff algometer will measure cPDT. Participants will be fitted with 13-cm-wide silicone tourniquet cuffs (VBM, Düsseldorf, Germany) on bilateral lower limbs. The cuff inflation will be controlled by a cuff algometry system (Cortex Technology, Hadsund, Denmark). The cuff will be inflated at a rate of 1kPa/s to a maximum of 100 kPa. Using a hand-held electronic device with a release button for deflating the cuff, participants will be instructed to rate the pressure pain continuously on a 10-cm visual analogue scale (VAS), until the pain becomes intolerable, at which point they will press the release button to terminate the test. The cPDT will be the cuff pressure reading at the time of VAS rating of 1cm. The cuff-system is user independent and has been shown to be reliable for the outcomes assessed.
Measured: pre-walking, immediately post-walking
Change from pre-walking to immediately post-walking in Cuff Pain Tolerance Threshold (cPTT)
A computer-controlled cuff algometer will measure cPDT. Participants will be fitted with 13-cm-wide silicone tourniquet cuffs (VBM, Düsseldorf, Germany) on bilateral lower limbs. The cuff inflation will be controlled by a cuff algometry system (Cortex Technology, Hadsund, Denmark). The cuff will be inflated at a rate of 1kPa/s to a maximum of 100 kPa. Using a hand-held electronic device with a release button for deflating the cuff, participants will be instructed to rate the pressure pain continuously on a 10-cm visual analogue scale (VAS), until the pain becomes intolerable, at which point they will press the release button to terminate the test. The cPTT will be the cuff pressure reading at the time of test termination (i.e., when the pain becomes intolerable). If the tolerance threshold is not achieved before the 100 kPa limit, cPTT will be 100 kPa. The cuff-system is user independent and has been shown to be reliable for the outcomes assessed.
Measured: pre-walking, immediately post-walking
Change from pre-walking to immediately post-walking in Temporal Summation of Pain (TSP)
Using the same cuff algometry system, the TSP will be assessed by delivering 10 rapid cuff pressure stimuli at a pressure magnitude of the cPTT lasting for one second. Each stimulus will be followed by 1-second break before the next stimulus. Participants will be instructed to rate the pain intensity on the electronic VAS for each stimulus without returning the VAS to zero between inflations. The VAS score will be recorded for each stimulus. This procedure has been shown to be reliable with Intraclass Correlation Coefficients of 0.70-0.77.
Measured: pre-walking, immediately post-walking
Change from pre-walking to immediately post-walking in Conditioned Pain Modulation (CPM)
The CPM will be assessed by re-measuring the cPDT of the index limb during a simultaneously painful conditioning stimulus on the non-index limb. An increase in cPDT from baseline would indicate a CPM response.
Measured: pre-walking, immediately post-walking
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted21 Nov 2022
- Study start20 Apr 2023
- Primary completion31 Jul 2024
- Study completion31 Jul 2024
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.
- More trials run by Northwestern UniversityThe sponsor's other registered studies.
- 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
- Crossover
- Model description
- This is a randomized, controlled, single-blinded trial, with a 2-arm crossover design.
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 23 participants (actual)
Sponsor and investigators
- Lead sponsor
- Northwestern University
- Sponsor type
- University, hospital or other
- Collaborators
- Aalborg University
- Responsible party
- Sponsor
- Investigators
- Alison H Chang, Principal investigator, Aalborg UniversityMichael Rathleff, Study director, Aalborg University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05623683
- Sponsor's protocol ID
- N-20220047
- Acronym
- P4ACE
- Status last verified
- Jul 2025
- First submitted
- 12 Nov 2022
- Last updated
- 28 Jul 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 28 Jul 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Pain Profiles and Patterns of Physical Activity in Persons With Chronic Knee Pain
- ClinicalTrials.gov ID
- NCT05623683
- Acronym / sponsor ID
- P4ACE / N-20220047
- Conditions
- Knee Osteoarthritis
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 23 participants (actual)
- Lead sponsor
- Northwestern UniversityUniversity, hospital or other
- Collaborators
- Aalborg University
- Study start
- 20 Apr 2023 (actual)
- Primary completion
- 31 Jul 2024 (actual)
- Study completion
- 31 Jul 2024 (actual)
- First posted
- 21 Nov 2022 (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.
The goal of this single-blind, cross-over clinical trial is to compare the immediate effect of intermittent vs. continuous walking on clinical and mechanistic pain profiles in persons with knee osteoarthritis (OA). In this cross-over trial, participants will perform two types of walking on a treadmill. Intermittent walking will involve 3 blocks of 10 minutes with 2 blocks of 5-minute rest (sitting on a chair) in-between. Continuous walking will involve resting for 10 minutes (sitting in a chair) before walking on the treadmill for 1 continuous block of 30 minutes.
Detailed description
The study objectives are to compare the immediate effect of intermittent vs. continuous walking on clinical and mechanistic pain profiles in persons with knee osteoarthritis (OA). The investigators hypothesize that continuous walking will result in greater increases in clinical pain and mechanistic pain sensitivity than intermittent walking. Physical activity (PA) has been recommended as the first-line management strategy for people with chronic knee pain. Walking is an accessible, low-cost, joint-friendly form of PA and is widely advocated for older adults with knee complaints. However, movement-evoked pain is a commonly cited barrier for PA engagement. On one hand, a bout of PA may produce short-term analgesia and reduce pain. On the other hand, excessive or prolonged PA may exacerbate symptoms and lead to avoidance/fear of subsequent PA. Besides the total PA volume, how it is accumulated could also impact joint health. It is biomechanically plausible that shorter and frequent activities are more beneficial to articular tissues than longer and infrequent activities. Compared to intermittent loading, prolonged continuous loading had a detrimental effect on the biomechanical functions of articular cartilage in a bovine model. Findings of this study will provide insight on the relations between patterns of PA and pain profiles.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Crossover
- Masking
- Single blind (participant)
- Number of arms
- 2
- Model description
- This is a randomized, controlled, single-blinded trial, with a 2-arm crossover design.
| Arm | Type | Receives |
|---|---|---|
| Intermittent Walking | Active comparator | Other: Intermittent WalkingIntermittent walking on the treadmill |
| Continuous Walking | Active comparator | Other: Continuous WalkingContinuous walking on the treadmill |
Who may qualify
- Ages
- 45 to 75 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (9 listed)
- men or women aged 45-75 years
- BMI ≤ 35 kg/m2
- frequent movement-related knee pain (knee pain on more than half the days of the past month)
- no morning stiffness or morning stiffness lasting < 30-min
- self-reported unilateral or bilateral knee pain of ≥ 3 and ≤ 7 on a 0-10 numeric pain rating scale (NPRS)
Key exclusion criteria (6 listed)
- intra-articular steroid injections in the previous 3 months
- intra-articular hyaluronic acid injection in the previous 6 months
- any arthroscopic or surgical knee procedures (e.g., partial meniscectomy) in the past 12 months
- lumbar radiculopathy
- neurological, vestibular, or visual dysfunction affecting walking balance and mobility
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 |
|---|---|---|
| Intermittent WalkingWearing comfortable clothes and their usual walking shoes, participants will walk on a treadmill to accrue 30 minutes of walking. Participants will be instructed not to use the treadmill side rails for balance or support during walking. Participants will walk on the treadmill for 3 blocks of 10 minutes with 2 blocks of 5-minute rest (sitting on a chair) in-between. A safety button to stop the treadmill will be available to the participants, so they can stop walking anytime. If participants feel that they are about to lose balance, they are allowed to hold on to the side rails to regain balance and terminate the trial. | Other | Intermittent Walking |
| Continuous WalkingWearing comfortable clothes and their usual walking shoes, participants will walk on a treadmill to accrue 30 minutes of walking. Participants will be instructed not to use the treadmill side rails for balance or support during walking. Participants will rest for 10 minutes (sitting in a chair) before walking on the treadmill for 1 continuous block of 30 minutes. A safety button to stop the treadmill will be available to the participants, so they can stop walking anytime. If participants feel that they are about to lose balance, they are allowed to hold on to the side rails to regain balance and terminate the trial. | Other | Continuous Walking |
Primary outcome
Change from pre-walking to immediately post-walking in Numeric Pain Rating Scale (NPRS) for current knee pain
Time frame: pre-walking, immediately post-walking
The primary outcome is the self-reported clinical pain. The pre- and post-walking knee pain will be rated right before the commencement of the walking program and at the termination of the walking program respectively. Participants verbally select a value that corresponds with the intensity of pain that they experience. "0" means "no pain" and "10" means "pain as bad as you can imagine" or "worst pain imaginable". The NPRS, an 11-point (i.e., 0-10) measure of pain intensity, is recommended as a core outcome measure in clinical trials of chronic pain treatments and has excellent reliability and validity for adults with chronic musculoskeletal pain. On average, a change of 2 points or a change of approximately 30% in NPRS represented a clinically important difference in adults with chronic pain.
4 secondary outcomes
Change from pre-walking to immediately post-walking in Cuff Pain Detection Threshold (cPDT)
Time frame: pre-walking, immediately post-walking
Change from pre-walking to immediately post-walking in Cuff Pain Tolerance Threshold (cPTT)
Time frame: pre-walking, immediately post-walking
Change from pre-walking to immediately post-walking in Temporal Summation of Pain (TSP)
Time frame: pre-walking, immediately post-walking
Change from pre-walking to immediately post-walking in Conditioned Pain Modulation (CPM)
Time frame: pre-walking, immediately post-walking
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 28 Jul 2025.
- Individual participant dataSharing planned: No
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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. This study is not recruiting at the moment.
Alison H Chang principal investigator
Aalborg University
Michael Rathleff study director
Aalborg University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Intermittent Walking and Continuous Walking in people with Knee Osteoarthritis, run by Northwestern University at 1 site in Denmark.
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 9 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: finished, as of the sponsor's last update on 28 Jul 2025. 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 Denmark. 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?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change from pre-walking to immediately post-walking in Numeric Pain Rating Scale (NPRS) for current knee pain (time frame: pre-walking, immediately post-walking). 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 Jul 2025.