Knee OsteoarthritisLDRT-KOANCT07886697
Low-Dose Radiotherapy for Painful Knee Osteoarthritis
A study testing Low-Dose Radiotherapy (LDRT) in people with Knee Osteoarthritis, run by Universidad Rey Juan Carlos at 4 sites in Spain.
Trial summary
Knee osteoarthritis is a common cause of chronic pain and difficulty with everyday activities, particularly in older adults. Some patients continue to experience clinically relevant knee pain despite medication, therapeutic exercise, physiotherapy, or other conservative treatments. Read more about this study
- Who is it for?
- Ages 60 years and older
- Conditions the study is for
- Knee Osteoarthritis
- What is being tested?
- Low-Dose Radiotherapy (LDRT)
- Type of treatment
- Pill or oral medicine, Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 283 participants
- Where
- 4 sitesSpain
- Study dates
- 15 Oct 2026to 30 Jun 2027
- 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 60 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Age 60 years or older.
- Clinical and radiographic diagnosis of primary knee osteoarthritis.
- Kellgren-Lawrence grade II or III osteoarthritis in the index knee.
- Pain in the index knee for at least 6 months.
- Baseline average index-knee pain intensity greater than 4 on a 0-to-10
- Numerical Rating Scale (NRS), referring to the previous 7 days.
Show all 10Show fewer
- Persistent clinically relevant knee pain despite documented prior conservative management. Conservative management must include pharmacological treatment appropriate to the participant's clinical profile and therapeutic exercise and/or physiotherapy. If any of these measures were not undertaken because of contraindication, intolerance, or clinical inability, the reason must be documented.
- Radiograph of the index knee performed within 6 months before inclusion and adequate to confirm the diagnosis and Kellgren-Lawrence grade. A new radiograph will be obtained if no valid recent examination is available.
- Ability to understand the study procedures and reliably complete the required clinical assessments and questionnaires.
- Written informed consent to participate in the study.
Who cannot join
- Kellgren-Lawrence grade 0, I, or IV in the index knee.
- Knee prosthesis in the index knee.
- Previous radiotherapy involving the treatment region.
- Body mass index greater than 39 kg/m².
- Active connective tissue disease with clinically relevant skin or soft-tissue involvement in the treatment region, including active systemic lupus erythematosus or rheumatoid arthritis when considered clinically relevant for radiotherapy.
- Fibromyalgia or a psychiatric disorder that, in the investigator's judgment, would substantially compromise reliable assessment of pain or patient-reported outcomes.
- Inability to provide informed consent or to reliably complete the required study assessments.
- Intra-articular corticosteroid injection, intra-articular hyaluronic acid injection, or radiofrequency procedure involving the index knee within the 2 months before inclusion.
Trial locations and contacts
4 sites in 1 country. Contact the study team or a site near you to ask about taking part.
Spain4 sites
Hospital Universitario de Fuenlabrada
Fuenlabrada, Madrid, 28942
Dolores Bedmar, MD, PhD, +34 916 006 325, mariadolores.bedmar@salud.madrid.org
Enrique Barrós, MD, MSc, +34 626 972 413, e.barros.2023@alumnos.urjc.es
Hospital Universitario Clínico San Cecilio
Granada, Granada, 18016
Vanessa Jerviz, MD, +34 958 840 980, vanessa.jerviz.sspa@juntadeandalucia.es
Hospital Ascires Valencia
Valencia, Valencia, 46014
Jorge Pastor, MD, +34 963 873 050, hospital@ascires.com
Hospital General Universitario de Valencia
Valencia, Valencia, 46014
Dolores López, MD, +34 963 131 800 ext. 437654, udo_hguv@gva.es
About this study
Official title: Low-Dose Radiotherapy for Painful Knee Osteoarthritis: A Multicenter, Interdisciplinary, Prospective Single-Arm Study
Knee osteoarthritis is a common cause of chronic pain and difficulty with everyday activities, particularly in older adults. Some patients continue to experience clinically relevant knee pain despite medication, therapeutic exercise, physiotherapy, or other conservative treatments.
This prospective, multicenter study will evaluate changes in pain, physical function, health-related quality of life, and safety after low-dose radiotherapy (LDRT) in adults aged 60 years or older with painful primary knee osteoarthritis. All participants will receive the same treatment, and there will be no control or sham-treatment group.
Read more
Participants will receive one course of low-dose radiotherapy to the study knee, consisting of six fractions of 0.5 Gy, for a total dose of 3.0 Gy, administered twice weekly on nonconsecutive days over approximately 3 weeks.
Clinical assessments will be performed before treatment and approximately 45 and 90 days after the last radiotherapy fraction. The main outcome is the change from baseline to Day 90 in average knee pain during the previous 7 days, measured on a 0-to-10 Numerical Rating Scale. The study hypothesis is that average knee pain will be lower at Day 90 than before treatment. Other outcomes include physical function, health-related quality of life, the participant's overall assessment of the affected knee, pain response, analgesic use, treatment completion, additional knee treatments, and adverse events.
Read the detailed description
Low-dose radiotherapy (LDRT) has been used in several European countries for painful degenerative musculoskeletal disorders, including knee osteoarthritis. Clinical studies have reported improvements in pain and function after LDRT, although findings from controlled trials have been heterogeneous and uncertainty remains regarding the magnitude of the treatment-specific effect. This study is designed to prospectively characterize clinical changes following a standardized LDRT regimen in patients with painful primary knee osteoarthritis treated across multiple centers.
This is a prospective, multicenter, interdisciplinary, open-label, non-randomized, single-group interventional study. A total of 283 participants aged 60 years or older with symptomatic primary knee osteoarthritis will be enrolled. Each participant will contribute one index knee; in participants with bilateral knee osteoarthritis, the more painful knee will be designated as the index knee.
All participants will receive one continuous course of LDRT consisting of six fractions of 0.5 Gy, for a total dose of 3.0 Gy. Fractions will be administered twice weekly on nonconsecutive days over approximately 3 weeks. Treatment will be planned using computed tomography and delivered using a standardized technique across participating centers. No second protocol-scheduled radiotherapy course will be administered before completion of the Day 90 assessment.
Participants will be evaluated before treatment and at approximately 45 and 90 days after the last radiotherapy fraction. The primary analysis will assess the change from baseline to Day 90 in average pain intensity in the index knee during the previous 7 days, measured using an 11-point Numerical Rating Scale. Additional assessments will evaluate pain, stiffness, physical function, health-related quality of life, global patient assessment, clinically relevant pain response, analgesic treatment, co-interventions, treatment adherence, and adverse events.
Because the study has no concurrent control or sham-treatment group, observed changes after treatment cannot be attributed exclusively to radiotherapy. The study is intended to estimate within-participant longitudinal changes after a standardized LDRT intervention and to describe clinical response and safety in routine multicenter practice. Potential contributions from the natural course of osteoarthritis, regression to the mean, participant expectations, and concomitant treatments will be considered when interpreting the results.
- Conditions
- Knee Osteoarthritis
- Being tested
- Low-Dose Radiotherapy (LDRT)
- Keywords
- Low-Dose Radiotherapy, Painful Knee Osteoarthritis, Knee Pain, LDRT, Radiotherapy for Benign Disease, Degenerative Joint Disease
- Medical subject headings
- Osteoarthritis, Knee, Joint Diseases
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Low-Dose Radiotherapy (LDRT)Radiation
Low-dose radiotherapy will be delivered to the index knee as six fractions of 0.5 Gy each, for a total prescribed dose of 3.0 Gy. Fractions will be administered twice weekly on nonconsecutive days over approximately 3 weeks. Treatment will be planned using computed tomography simulation. The clinical target volume will include the relevant femoral and tibial articular and subchondral surfaces, joint capsule, synovium, and periarticular tissues. A nominal 5-mm planning target volume margin will be applied. Treatment will be delivered using opposed anteroposterior and posteroanterior fields with 6-MV photons.
| Study group | Role | What they receive |
|---|---|---|
| Low-Dose Radiotherapy | Experimental | Participants will receive a single course of low-dose radiotherapy to the index knee consisting of six fractions of 0.5 Gy, for a total dose of 3.0 Gy, administered twice weekly on nonconsecutive days over approximately 3 weeks. Receives: Radiation: Low-Dose Radiotherapy (LDRT) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change From Baseline in Average Index-Knee Pain Intensity at Day 90
Average pain intensity in the index knee during the previous 7 days will be assessed using an 11-point Numerical Rating Scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain). Change will be calculated as baseline NRS minus Day 90 NRS. Positive values indicate improvement, zero indicates no change, and negative values indicate worsening.
Measured: Baseline and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Secondary outcomes (15)
Change From Baseline in Average Index-Knee Pain Intensity at Day 45
Average pain intensity in the index knee during the previous 7 days will be assessed using an 11-point Numerical Rating Scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain). Change will be calculated as baseline NRS minus Day 45 NRS. Positive values indicate improvement, zero indicates no change, and negative values indicate worsening.
Measured: Baseline and Day 45 (45 ± 7 days after the last radiotherapy fraction)
Change From Baseline in WOMAC Pain Subscale Score
The WOMAC pain subscale consists of 5 items, each scored from 0 to 4, yielding a total score from 0 to 20. Higher scores indicate greater pain. Change from baseline will be assessed at Day 45 and Day 90.
Measured: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in WOMAC Stiffness Subscale Score
The WOMAC stiffness subscale consists of 2 items, each scored from 0 to 4, yielding a total score from 0 to 8. Higher scores indicate greater stiffness. Change from baseline will be assessed at Day 45 and Day 90.
Measured: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in WOMAC Physical Function Subscale Score
The WOMAC physical function subscale consists of 17 items, each scored from 0 to 4, yielding a total score from 0 to 68. Higher scores indicate greater functional limitation. Change from baseline will be assessed at Day 45 and Day 90.
Measured: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in KOOS-PS Score
The 7-item Knee injury and Osteoarthritis Outcome Score-Physical Function Shortform (KOOS-PS) will be used to assess physical function. The raw score will be transformed to a 0-to-100 Rasch-based score, where 0 indicates no difficulty and 100 indicates extreme difficulty. Change from baseline will be assessed at Day 45 and Day 90.
Measured: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in EQ-5D-3L Health Utility Index
Health-related quality of life will be assessed using the Spanish EQ-5D-3L. The health utility index will be calculated from the five dimensions using the Spanish value set. Higher index values indicate better health status. Change from baseline will be assessed at Day 45 and Day 90.
Measured: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in EQ VAS Score
Overall health status will be assessed using the EQ Visual Analogue Scale (EQ VAS), ranging from 0 to 100, where 0 represents the worst imaginable health state and 100 represents the best imaginable health state. Change from baseline will be assessed at Day 45 and Day 90.
Measured: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in Patient Global Assessment of the Index Knee
Patient Global Assessment (PGA) will evaluate the overall impact of index-knee osteoarthritis during the previous 7 days using a 0-to-100 scale. Participants will answer: "Considering all the ways in which the osteoarthritis of your index knee affects you, how would you rate your knee during the past 7 days?" A score of 0 indicates very well/no impact and 100 indicates very poorly/maximum impact. Change from baseline will be assessed at Day 45 and Day 90.
Measured: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Proportion of Participants With at Least a 30% Reduction in NRS Pain Intensity
A pain responder will be defined as a participant with at least a 30% reduction from baseline in average index-knee pain intensity measured using the 0-to-10 Numerical Rating Scale (NRS). Percentage reduction will be calculated as [(baseline NRS - follow-up NRS) / baseline NRS] × 100. The proportion of participants meeting this criterion will be assessed at Day 45 and Day 90.
Measured: Day 45 (45 ± 7 days after the last radiotherapy fraction) and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Proportion of Participants With at Least a 50% Reduction in NRS Pain Intensity
A pain responder will be defined as a participant with at least a 50% reduction from baseline in average index-knee pain intensity measured using the 0-to-10 Numerical Rating Scale (NRS). Percentage reduction will be calculated as [(baseline NRS - follow-up NRS) / baseline NRS] × 100. The proportion of participants meeting this criterion will be assessed at Day 45 and Day 90.
Measured: Day 45 (45 ± 7 days after the last radiotherapy fraction) and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Proportion of Participants Meeting OMERACT-OARSI Responder Criteria
Participants will be classified as OMERACT-OARSI responders if they meet either of the following criteria: (1) high improvement in pain or physical function, defined as an improvement of at least 50% and an absolute improvement of at least 20 points on a 0-to-100 scale; or (2) improvement in at least 2 of 3 domains-pain, physical function, and Patient Global Assessment-defined as an improvement of at least 20% and an absolute improvement of at least 10 points on a 0-to-100 scale. The proportion of responders will be assessed at Day 45 and Day 90.
Measured: Day 45 (45 ± 7 days after the last radiotherapy fraction) and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Participants With Changes in Analgesic Treatment or Rescue Medication Use
Changes in analgesic treatment for index-knee osteoarthritis will be recorded throughout follow-up, including initiation, discontinuation, or dose modification of analgesic medication and use of rescue medication. The proportion of participants with at least one change in analgesic treatment or rescue medication use will be summarized through Day 90.
Measured: From baseline through Day 90 (90 ± 14 days after the last radiotherapy fraction)
Participants Receiving an Index-Knee Co-intervention During Follow-up
Index-knee co-interventions during follow-up will be recorded, including intra-articular corticosteroid or hyaluronic acid injections, radiofrequency procedures, other interventional procedures, or surgery. The proportion of participants receiving at least one such co-intervention will be summarized through Day 90.
Measured: From baseline through Day 90 (90 ± 14 days after the last radiotherapy fraction)
Proportion of Participants Completing the Planned Radiotherapy Course
Treatment completion will be defined as receipt of all six planned radiotherapy fractions of 0.5 Gy each, corresponding to a total prescribed dose of 3.0 Gy to the index knee. The proportion of participants completing the planned radiotherapy course will be summarized.
Measured: From the first radiotherapy fraction through completion of the planned course (approximately 3 weeks)
Incidence and Severity of Adverse Events
Adverse events occurring from the first radiotherapy fraction through Day 90 will be recorded and graded according to the Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. For each event, the event term, severity grade, onset and resolution dates, relationship to radiotherapy, actions taken, treatment required, and outcome will be documented. The incidence and severity of adverse events will be summarized.
Measured: From the first radiotherapy fraction through Day 90 (90 ± 14 days after the last radiotherapy fraction)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted21 Oct 2026
- Study start15 Oct 2026 (estimated)
- Primary completion30 Jun 2027 (estimated)
- Study completion30 Jun 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (5)Papers the sponsor has linked to this study.
- 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
- All participants will receive the same standardized low-dose radiotherapy regimen. There is no comparator, control, or sham-treatment arm.
- Masking
- None (open label)
- Enrolment
- 283 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Universidad Rey Juan Carlos
- Sponsor type
- University, hospital or other
- Collaborators
- Hospital Universitario de Fuenlabrada, Hospital General Universitario de Valencia, Hospital Universitario Clínico San Cecilio, Ascires Grupo Biomédico
- Responsible party
- Principal investigator, Enrique Barrós Beracaza, MD, Universidad Rey Juan Carlos
- Investigators
- Enrique Barrós, MD, MSc, Study director, Universidad Rey Juan Carlos
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07886697
- Sponsor's protocol ID
- LDRT-KOA-MC-01
- Other IDs
- 24/63
- Acronym
- LDRT-KOA
- Status last verified
- Oct 2026
- First submitted
- 14 Oct 2026
- Last updated
- 21 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: Pega esta versión: There is no plan for routine public sharing of individual participant data because access is subject to applicable data protection requirements, ethics approvals, and institutional agreements. However, justified requests for access to study data may be evaluated by the study team and the responsible institutions on a case-by-case basis, provided that appropriate ethical, legal, and data protection requirements are met.
Publications
Muller JA, Alsalloum J, Vordermark D, Delank S. KORT - Knee osteoarthrosis radiotherapy trial: Protocol for a multidisciplinary pathway and a planned sham-controlled phase III trial of low-dose radiotherapy in knee osteoarthritis. Osteoarthr Cartil Open. 2026 Feb 27;8(2):100764. doi: 10.1016/j.ocarto.2026.100764. eCollection 2026 Jun.
PubMed 41859527Fazilat-Panah D, Javadinia SA, Shabestani Monfared A, Attarian F, Babaei M, Yousefghahari B, Najafzadeh Sadati S, Ahmadi N, Fallah Tafti H. Effects of low dose rate radiotherapy on pain relief, performance score, and quality of life in patients with knee osteoarthritis; a double-blind sham-controlled randomized clinical trial. Int J Radiat Biol. 2025;101(5):541-548. doi: 10.1080/09553002.2025.2473975. Epub 2025 Mar 5.
PubMed 40043233Kim BH, Shin K, Kim MJ, Kim HJ, Ro DH, Wang JH, Lee DH, Kim DH, Sun J, Lee JH, Kim JY, Hong EH, Cho SJ, Han HS, Park W. Low-dose RaDiation therapy for patients with KNee osteoArthritis (LoRD-KNeA): a protocol for a sham-controlled randomised trial. BMJ Open. 2023 Feb 10;13(2):e069691. doi: 10.1136/bmjopen-2022-069691.
PubMed 36764712Mahler EAM, Minten MJ, Leseman-Hoogenboom MM, Poortmans PMP, Leer JWH, Boks SS, van den Hoogen FHJ, den Broeder AA, van den Ende CHM. Effectiveness of low-dose radiation therapy on symptoms in patients with knee osteoarthritis: a randomised, double-blinded, sham-controlled trial. Ann Rheum Dis. 2019 Jan;78(1):83-90. doi: 10.1136/annrheumdis-2018-214104. Epub 2018 Oct 26.
PubMed 30366945Niewald M, Muller LN, Hautmann MG, Dzierma Y, Melchior P, Graber S, Rube C, Fleckenstein J; working group "Benign diseases" of the DEGRO (German Society for Radiation Oncology). ArthroRad trial: multicentric prospective and randomized single-blinded trial on the effect of low-dose radiotherapy for painful osteoarthritis depending on the dose-results after 3 months' follow-up. Strahlenther Onkol. 2022 Apr;198(4):370-377. doi: 10.1007/s00066-021-01866-2. Epub 2021 Nov 1.
PubMed 34724085
Study at a glance
From the registry record, last updated by the sponsor on 21 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Low-Dose Radiotherapy for Painful Knee Osteoarthritis: A Multicenter, Interdisciplinary, Prospective Single-Arm Study
- ClinicalTrials.gov ID
- NCT07886697
- Acronym / sponsor ID
- LDRT-KOA / LDRT-KOA-MC-01
- Conditions
- Knee Osteoarthritis
- Keywords
- Low-Dose Radiotherapy, Painful Knee Osteoarthritis, Knee Pain, LDRT, Radiotherapy for Benign Disease, Degenerative Joint Disease
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 283 participants (estimated)
- Lead sponsor
- Universidad Rey Juan CarlosUniversity, hospital or other
- Collaborators
- Hospital Universitario de Fuenlabrada, Hospital General Universitario de Valencia, Hospital Universitario Clínico San Cecilio, Ascires Grupo Biomédico
- Study start
- 15 Oct 2026 (estimated)
- Primary completion
- 30 Jun 2027 (estimated)
- Study completion
- 30 Jun 2027 (estimated)
- First posted
- 21 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 is a common cause of chronic pain and difficulty with everyday activities, particularly in older adults. Some patients continue to experience clinically relevant knee pain despite medication, therapeutic exercise, physiotherapy, or other conservative treatments.
This prospective, multicenter study will evaluate changes in pain, physical function, health-related quality of life, and safety after low-dose radiotherapy (LDRT) in adults aged 60 years or older with painful primary knee osteoarthritis. All participants will receive the same treatment, and there will be no control or sham-treatment group.
Participants will receive one course of low-dose radiotherapy to the study knee, consisting of six fractions of 0.5 Gy, for a total dose of 3.0 Gy, administered twice weekly on nonconsecutive days over approximately 3 weeks.
Clinical assessments will be performed before treatment and approximately 45 and 90 days after the last radiotherapy fraction. The main outcome is the change from baseline to Day 90 in average knee pain during the previous 7 days, measured on a 0-to-10 Numerical Rating Scale. The study hypothesis is that average knee pain will be lower at Day 90 than before treatment. Other outcomes include physical function, health-related quality of life, the participant's overall assessment of the affected knee, pain response, analgesic use, treatment completion, additional knee treatments, and adverse events.
Detailed description
Low-dose radiotherapy (LDRT) has been used in several European countries for painful degenerative musculoskeletal disorders, including knee osteoarthritis. Clinical studies have reported improvements in pain and function after LDRT, although findings from controlled trials have been heterogeneous and uncertainty remains regarding the magnitude of the treatment-specific effect. This study is designed to prospectively characterize clinical changes following a standardized LDRT regimen in patients with painful primary knee osteoarthritis treated across multiple centers.
This is a prospective, multicenter, interdisciplinary, open-label, non-randomized, single-group interventional study. A total of 283 participants aged 60 years or older with symptomatic primary knee osteoarthritis will be enrolled. Each participant will contribute one index knee; in participants with bilateral knee osteoarthritis, the more painful knee will be designated as the index knee.
All participants will receive one continuous course of LDRT consisting of six fractions of 0.5 Gy, for a total dose of 3.0 Gy. Fractions will be administered twice weekly on nonconsecutive days over approximately 3 weeks. Treatment will be planned using computed tomography and delivered using a standardized technique across participating centers. No second protocol-scheduled radiotherapy course will be administered before completion of the Day 90 assessment.
Participants will be evaluated before treatment and at approximately 45 and 90 days after the last radiotherapy fraction. The primary analysis will assess the change from baseline to Day 90 in average pain intensity in the index knee during the previous 7 days, measured using an 11-point Numerical Rating Scale. Additional assessments will evaluate pain, stiffness, physical function, health-related quality of life, global patient assessment, clinically relevant pain response, analgesic treatment, co-interventions, treatment adherence, and adverse events.
Because the study has no concurrent control or sham-treatment group, observed changes after treatment cannot be attributed exclusively to radiotherapy. The study is intended to estimate within-participant longitudinal changes after a standardized LDRT intervention and to describe clinical response and safety in routine multicenter practice. Potential contributions from the natural course of osteoarthritis, regression to the mean, participant expectations, and concomitant treatments will be considered when interpreting the results.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- All participants will receive the same standardized low-dose radiotherapy regimen. There is no comparator, control, or sham-treatment arm.
| Arm | Type | Receives |
|---|---|---|
| Low-Dose Radiotherapy | Experimental | Radiation: Low-Dose Radiotherapy (LDRT)Participants will receive a single course of low-dose radiotherapy to the index knee consisting of six fractions of 0.5 Gy, for a total dose of 3.0 Gy, administered twice weekly on nonconsecutive days over approximately 3 weeks. |
Who may qualify
- Ages
- 60 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (10 listed)
- Age 60 years or older.
- Clinical and radiographic diagnosis of primary knee osteoarthritis.
- Kellgren-Lawrence grade II or III osteoarthritis in the index knee.
- Pain in the index knee for at least 6 months.
- Baseline average index-knee pain intensity greater than 4 on a 0-to-10
Key exclusion criteria (8 listed)
- Kellgren-Lawrence grade 0, I, or IV in the index knee.
- Knee prosthesis in the index knee.
- Previous radiotherapy involving the treatment region.
- Body mass index greater than 39 kg/m².
- Active connective tissue disease with clinically relevant skin or soft-tissue involvement in the treatment region, including active systemic lupus erythematosus or rheumatoid arthritis when considered clinically relevant for radiotherapy.
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 |
|---|---|---|
| Low-Dose Radiotherapy (LDRT)Low-dose radiotherapy will be delivered to the index knee as six fractions of 0.5 Gy each, for a total prescribed dose of 3.0 Gy. Fractions will be administered twice weekly on nonconsecutive days over approximately 3 weeks. Treatment will be planned using computed tomography simulation. The clinical target volume will include the relevant femoral and tibial articular and subchondral surfaces, joint capsule, synovium, and periarticular tissues. A nominal 5-mm planning target volume margin will be applied. Treatment will be delivered using opposed anteroposterior and posteroanterior fields with 6-MV photons. | Radiation | Low-Dose Radiotherapy |
Primary outcome
Change From Baseline in Average Index-Knee Pain Intensity at Day 90
Time frame: Baseline and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Average pain intensity in the index knee during the previous 7 days will be assessed using an 11-point Numerical Rating Scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain). Change will be calculated as baseline NRS minus Day 90 NRS. Positive values indicate improvement, zero indicates no change, and negative values indicate worsening.
15 secondary outcomes
Change From Baseline in Average Index-Knee Pain Intensity at Day 45
Time frame: Baseline and Day 45 (45 ± 7 days after the last radiotherapy fraction)
Change From Baseline in WOMAC Pain Subscale Score
Time frame: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in WOMAC Stiffness Subscale Score
Time frame: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in WOMAC Physical Function Subscale Score
Time frame: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in KOOS-PS Score
Time frame: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in EQ-5D-3L Health Utility Index
Time frame: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in EQ VAS Score
Time frame: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Change From Baseline in Patient Global Assessment of the Index Knee
Time frame: Baseline, Day 45 (45 ± 7 days after the last radiotherapy fraction), and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Proportion of Participants With at Least a 30% Reduction in NRS Pain Intensity
Time frame: Day 45 (45 ± 7 days after the last radiotherapy fraction) and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Proportion of Participants With at Least a 50% Reduction in NRS Pain Intensity
Time frame: Day 45 (45 ± 7 days after the last radiotherapy fraction) and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Proportion of Participants Meeting OMERACT-OARSI Responder Criteria
Time frame: Day 45 (45 ± 7 days after the last radiotherapy fraction) and Day 90 (90 ± 14 days after the last radiotherapy fraction)
Participants With Changes in Analgesic Treatment or Rescue Medication Use
Time frame: From baseline through Day 90 (90 ± 14 days after the last radiotherapy fraction)
Participants Receiving an Index-Knee Co-intervention During Follow-up
Time frame: From baseline through Day 90 (90 ± 14 days after the last radiotherapy fraction)
Proportion of Participants Completing the Planned Radiotherapy Course
Time frame: From the first radiotherapy fraction through completion of the planned course (approximately 3 weeks)
Incidence and Severity of Adverse Events
Time frame: From the first radiotherapy fraction through Day 90 (90 ± 14 days after the last radiotherapy fraction)
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 21 Oct 2026.
- Background: PubMed 41859527Muller JA, Alsalloum J, Vordermark D, Delank S. KORT - Knee osteoarthrosis radiotherapy trial: Protocol for a multidisciplinary pathway and a planned sham-controlled phase III trial of low-dose radiotherapy in knee osteoarthritis. Osteoarthr Cartil Open. 2026 Feb 27;8(2):100764. doi: 10.1016/j.ocarto.2026.100764. eCollection 2026 Jun.
- Background: PubMed 40043233Fazilat-Panah D, Javadinia SA, Shabestani Monfared A, Attarian F, Babaei M, Yousefghahari B, Najafzadeh Sadati S, Ahmadi N, Fallah Tafti H. Effects of low dose rate radiotherapy on pain relief, performance score, and quality of life in patients with knee osteoarthritis; a double-blind sham-controlled randomized clinical trial. Int J Radiat Biol. 2025;101(5):541-548. doi: 10.1080/09553002.2025.2473975. Epub 2025 Mar 5.
- Background: PubMed 36764712Kim BH, Shin K, Kim MJ, Kim HJ, Ro DH, Wang JH, Lee DH, Kim DH, Sun J, Lee JH, Kim JY, Hong EH, Cho SJ, Han HS, Park W. Low-dose RaDiation therapy for patients with KNee osteoArthritis (LoRD-KNeA): a protocol for a sham-controlled randomised trial. BMJ Open. 2023 Feb 10;13(2):e069691. doi: 10.1136/bmjopen-2022-069691.
- Background: PubMed 30366945Mahler EAM, Minten MJ, Leseman-Hoogenboom MM, Poortmans PMP, Leer JWH, Boks SS, van den Hoogen FHJ, den Broeder AA, van den Ende CHM. Effectiveness of low-dose radiation therapy on symptoms in patients with knee osteoarthritis: a randomised, double-blinded, sham-controlled trial. Ann Rheum Dis. 2019 Jan;78(1):83-90. doi: 10.1136/annrheumdis-2018-214104. Epub 2018 Oct 26.
- Background: PubMed 34724085Niewald M, Muller LN, Hautmann MG, Dzierma Y, Melchior P, Graber S, Rube C, Fleckenstein J; working group "Benign diseases" of the DEGRO (German Society for Radiation Oncology). ArthroRad trial: multicentric prospective and randomized single-blinded trial on the effect of low-dose radiotherapy for painful osteoarthritis depending on the dose-results after 3 months' follow-up. Strahlenther Onkol. 2022 Apr;198(4):370-377. doi: 10.1007/s00066-021-01866-2. Epub 2021 Nov 1.
- Individual participant dataSharing planned: No. Pega esta versión: There is no plan for routine public sharing of individual participant data because access is subject to applicable data protection requirements, ethics approvals, and institutional agreements. However, justified requests for access to study data may be evaluated by the study team and the responsible institutions on a case-by-case basis, provided that appropriate ethical, legal, and data protection requirements are met.
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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.
Enrique Barrós, MD, MSc study director
Universidad Rey Juan Carlos
4 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Low-Dose Radiotherapy (LDRT) in people with Knee Osteoarthritis, run by Universidad Rey Juan Carlos at 4 sites in Spain.
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 10 inclusion and 8 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 21 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 4 sites in Spain. 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 Dolores Bedmar, MD, PhD (+34 916 006 325, mariadolores.bedmar@salud.madrid.org), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change From Baseline in Average Index-Knee Pain Intensity at Day 90 (time frame: Baseline and Day 90 (90 ± 14 days after the last radiotherapy fraction)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07886697, which also lists 5 linked publications.
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 21 Oct 2026; AzTrials last refreshed its copy on 7 Nov 2026.