Knee osteoarthritis (KOA) is a degenerative joint disease that leads to functional limitations and pain and requires long-term management [1,2]. Worldwide, the number of patients with KOA increased by 122.42%, from 163,910,000 in 1990 to 36,4580,000 in 2019 [3]. With increasing obesity prevalence and aging of the global population, the incidence and years lived with disability and burden also increase [4].

KOA treatment is mainly indicated for pain management, functional recovery, and prevention of progression [5,6]. KOA recommendations can be divided into pharmacological, surgical, and nonpharmacological interventions [7,8]. Several guidelines have recommended the use of topical nonsteroidal anti-inflammatory drugs (NSAIDs) as first-line treatment, exercise, patient education, self-management, weight reduction as core treatment, and intra-articular injections, and oral NSAID therapy for persistent pain [5,7-10]. Because of the drug-related side effects and limited benefits of conventional pharmacological interventions, new treatments that can provide long-lasting pain reduction and achieve functional recovery must be developed [11,12].

Low-level laser therapy (LLLT) is a therapeutic approach for musculoskeletal diseases using light at wavelengths ranging from 632 to 904 nm, with an output power of < 500 mW [13]. The therapeutic effects of LLLT may be attributed to nonthermal and photochemical reactions (photobiomodulation) [14]. LLLT induces intracellular biochemical changes, such as the release of anti-inflammatory mediators, cellular oxygenation, and release of neurotransmitters involved in pain modulation [14,15]. Laser photobiomodulation with appropriate parameters exerted positive effects on cartilage defects in animal KOA models [16].

According to KOA guidelines, LT is not recommended as a core intervention for the treatment of KOA [1,5,9,10,17]. This may be due to its controversial clinical efficacy in treating KOA [18]. Despite some positive findings, Rayegani et al. [19] reported that significant heterogeneity in the findings of meta-analyses prevented drawing conclusions that LLLT improves function and alleviates pain in individuals with KOA. A systematic review and meta-analysis reported the lack of evidence on the efficacy of LLLT for KOA [20], whereas another meta-analysis suggested that LLLTs with 785–860 nm at 4–8 J per treatment site and 904 nm at 1–3 J per treatment site were effective in reducing pain and improving function in individuals with KOA [21]. Laser acupuncture (LA), which is a noninvasive irradiation of a low-level laser at an acupoint, was reported to effectively alleviate knee pain in individuals with KOA when performed with proper parameters [22].

Invasive LA (ILA) is a new LLLT modality, which involves laser irradiation from the tip of an acupuncture needle inserted into the acupoint using an acupuncture needle with an optic fiber inserted inside and attached to a laser-emitting machine [23]. A study demonstrated that 650-nm ILA inhibited the production of collagenase-induced inflammatory mediators of OA in rat models [24]. Previously, we revealed that 650-nm ILA significantly reduced pain and improved function in individuals with low back pain [25].

Despite the potential efficacy of ILA for KOA, clinical evidence on its usefulness in KOA is insufficient. Therefore, we aim to investigate the safety and efficacy of ILA on KOA through a pilot randomized controlled trial (RCT). The findings will provide a basis for a rigorous RCT designed to validate the effects of ILA on KOA.

This manuscript was written in compliance with the Standard Protocol Items: Recommendations for Interventional Trials Reporting Checklist [26].

1. Aims

1) The primary aim is to explore the efficacy of ILA (830- and 650-nm wavelengths) for treating KOA.

2) The secondary aim is to evaluate the safety of ILA (830- and 650-nm wavelengths) in individuals with KOA.

2. Hypothesis

1) ILA (830- and 650-nm wavelengths) will have a significant effect on individuals with KOA.

2) ILA (830- and 650-nm wavelengths) will be a safe intervention for individuals with KOA.

3. Study design

This parallel-arm, prospective, single-center, and patient-blinded pilot RCT will enroll 45 patients, who will be equally randomized to the 830, 650, and control groups. All patients will be educated on exercise and self-care. They will receive ILA treatment according to their group (control group, sham; 830 group, 830-nm wavelength; 650 group, 650-nm wavelength) for 10 minutes once a day, twice weekly for 6 weeks. Efficacy outcomes will be measured at baseline, visit after six treatments, 1 week after the last treatment, and 6 weeks after the last treatment. The details are shown in Table 1.

Table 1 . Study design in accordance with the Standard Protocol Items: Recommendations for Interventional Trials guideline.

	Study period
	Enrollment	Allocation	Post-allocation					Close-out
Timepoint	Screening		Visit 1	Visit 2–6	Visit 7	Visit 8–12	Visit 13	Visit 14
	Weeks		1	1–3	4	4–6	7	12
Enrollment
Informed consent	×
Sociodemographic profile	×
Medical history	×
Vital signs	×	×	×	×	×	×	×	×
Inclusion/exclusion criteria	×
Allocation		×
Visual analog scale	×
Interventions
Invasive laser acupuncture (sham, 830, or 650 nm)			×	×	×	×
Education on self-management and exercise			×	×	×	×
Assessments
Change in medical history			×	×	×	×	×	×
Safety assessment (incidence of adverse events)			×	×	×	×	×	×
Clinical laboratory test	×						×
Visual analog scale			×		×		×	×
European quality of life five-dimension five-level scale			×		×		×	×
Western Ontario and McMaster Universities Osteoarthritis Index			×		×		×	×
Patient’s global assessment			×		×		×	×
Doses of rescue medications			×		×		×	×

4. Ethical statement

The protocol (version 1.0) was approved by the Ministry of Food and Drug Safety (November 15, 2022; Medical Device Approval No. 1427). Version 1.1 was approved by the Institutional Review Board (IRB) of Dongshin University Gwangju Korean Medicine Hospital (July 18, 2023) and was registered with the Clinical Research Information Service (KCT0008860).

5. Recruitment

Recruitment will conducted at the Dongshin University Gwangju Korean Medicine Hospital Hospital, Republic of Korea, through advertisements on local newspapers, community posters, and Internet. The principal investigator (PI) or a subinvestigator will explain the purpose and harms of the study to interested individuals, who will provide voluntarily written informed consent before participation. Patients will be screened according to the inclusion and exclusion criteria. To ensure compliance with the protocol, the clinical research coordinator (CRC) will communicate and adjust the schedule at each visit.

6. Inclusion criteria

The inclusion criteria are as follows: 1) age 55–85 years, 2) diagnosis of KOA in accordance with the diagnostic criteria of the American College of Rheumatology [27], 3) knee pain persisting > 14 days per month for more than preceding 3 months, 4) presence of moderate knee pain (mean pain visual analog scale [VAS] score ranging from 35 to 74 at rest and during activity a week before screening), 5) stage 2 or 3 KOA in accordance with the Kellgren-Lawrence grade [28], and 6) provision of voluntary consent.

7. Exclusion criteria

The exclusion criteria are as follows: 1) previous total knee replacement, 2) posttraumatic KOA, 3) serious diseases (cancer, diabetic neuropathy, and severe hepatic, renal, cardiovascular, or central nervous system disease), 4) knee pain caused by trauma, tumor, inflammatory diseases, autoimmune diseases, rheumatoid arthritis, severe hip joint diseases, severe bow leg or knock knee, or gout, 5) history of mental illness (schizophrenia, serious anxiety, or depression) or drug or alcohol abuse within 6 months before screening, 6) injection with intra-articular mucus supplements (hylan, sodium hyaluronate, and hyaluronan) as KOA treatment 6 months before screening, 7) steroid injections into the knee joint, knee joint fluid drainage, or prolotherapy in the 3 months before screening, 8) current treatment for KOA, such as physical therapy, Korean medicine, or medications within 4 weeks before screening, 9) other diseases that require treatment for pain control, such as steroids or NSAIDs, 10) conditions in which ILA use is unsuitable, such as severe skin disease in the knee region, presence of metallic devices in the knee, electronic medical devices, or blood clotting abnormalities, 11) knee surgery within 1 year or is scheduled to undergo knee surgery during the study, 12) breastfeeding, pregnancy, or planning for pregnancy, and 13) participation in other studies within 8 weeks before screening or current participation in other trial.

8. Violation and dropout criteria

The violation criteria were as follows: 1) intervention compliance rate of < 75% or 2) serious deviation in implementation or remarkable protocol violation.

The dropout criteria were as follows: 1) incomplete data, 2) withdrawal of consent, 3) incidence of any serious adverse event (SAE), or 4) exclusion from the trial deemed necessary by the IRB or PI.

9. Randomization and allocation

After the initial screening and baseline evaluations, the 45 enrolled patients will be equally randomized to the 830, 650, or control groups in accordance with the randomization sequence generated by SAS^® version 9.4 (SAS Institute). A statistician who will not participate in the study will perform block randomization. A random number will be sealed in an opaque envelope and kept in a cabinet with double lock.

10. Implementation

An independent researcher will perform randomization and allocation. The CRC will carry out the enrolment procedures.

11. Blinding

To ensure that the practitioner administering the intervention would know the group assignment, a patient- and assessor-blinded design would be adopted. Sham and real lasers will have no differences in sound or sensation, and the assessor can only contact the participants at the time of evaluation. Thus, the assessor and participants would not know the group allocation until trial completion. If SAEs occur, unblinding will be allowed with IRB approval. All investigators will be educated on the blinding procedures.

12. Interventions

Trained Korean medical doctors will administer the intervention. To ensure adherence to the intervention protocol, the practitioners who will conduct the intervention will receive training. The intervention will be administered using a medical equipment (Ellise, WONTECH Co. Ltd.) composed of a laser output device, a disposable acupuncture needle with optical fibers inserted inside, and optical fiber-coupled laser diode (830 nm used GaAIAs; 650 nm used InGaAIP).

In the supine position with the participant’s knees bent, the acupuncture needle will be inserted in EX-LE4 (Neixiyan), ST35 (Dubi), ST34 (Liangqiu), SP10 (Xuehai), SP9 (Yinglingquan), GB34 (Yanglingquan), and EX-LE2 (Heding) acupoints on the lesion side (more painful side if bilateral), and the laser output device will be turned on for 10 minutes (830 group, 20 mW power; 650 group, 20 mW power; control group, 0 mW power). Manual stimulations will not be performed. The real laser parameters will be power of 20 mW, pulsed type of wave, energy dose of 12 J/point, frequency of 50 Hz, and power density of 63.69 W/cm². During the procedures, participants will be blindfolded, with no differences in sounds or feelings among the three groups. The detailed method of intervention is shown in Table 2 [29].

Table 2 . Revised STRICTA.

Item	Item criteria	Description
1. Acupuncture rationale	1a) Style of acupuncture	Laser acupuncture
	1b) Reasoning for the treatment provided-based on historical context, literature sources, and/or consensus methods, with references where appropriate	1) Discussion among three doctors who practice Korean medicine (consensus)
		2) Relevant articles [25]
		Selection of treatment regions based on related papers and expert discussions
	1c) Extent to which treatment varied	Standardized treatment
2. Details of needling	2a) Number of needle insertions per subject per session (mean and range where relevant)	One acupuncture will be inserted into one acupoint. Seven acupuncture needle will be used per session
	2b) Names (or location if no standard name) of points used (uni-/bilateral)	EX-LE4 (Neixiyan), ST35 (Dubi), ST34 (Liangqiu), SP10 (Xuehai), SP9 (Yinglingquan), GB34 (Yanglingquan), and EX-LE2 (Heding) on the lesion side (more painful side if bilateral)
	2c) Depth of insertion, based on a specified unit of measurement or on a particular tissue level	The acupuncture needle was inserted vertically or obliquely at a depth of 1–3 cm, depending the location of the needle
	2d) Responses sought	No de qi or muscle twitching–only sensation due to needle insertion
	2e) Needle stimulation	The real laser parameters will be power of 20 mW, pulsed type of wave, energy dose of 12 J/point, frequency of 50 Hz, and power density of 63.69 W/cm2
	2f) Needle retention time	10 minutes per session
	2g) Needle type	Disposable acupuncture needle with optical fibers inserted
3. Treatment regimen	3a) Number of treatment sessions	Twelve treatment sessions
	3b) Frequency and duration of treatment sessions	Twice/week for 6 weeks, 10 minutes per session
4. Other treatment components	4a) Details of other interventions administered to the acupuncture group	Education on exercise and self-care during their treatment visits
	4b) Setting and context of treatment–including instructions to practitioners–as well as information and explanations given to patients	To ensure adherence to the intervention protocol, practitioners who will conduct the intervention will receive training. All patients will be educated on exercise and self-care during treatment visits
5. Practitioner background	5a) Description of participating acupuncturists	Korean medicine doctor with the following qualifications: 6 years of formal university training in Korean medicine, a license
6. Control or comparator interventions	6a) Rationale for the control or comparator in the context of the research question, with sources that justify the choice	Relevant articles [25]
	6b) Precise description of the control or comparator; details for items 1–3 above with the use of sham acupuncture or any other type of acupuncture-like control	In the supine position with the participant’s knees bent, the acupuncture needle will be inserted in EX-LE4 (Neixiyan), ST35 (Dubi), ST34 (Liangqiu), SP10 (Xuehai), SP9 (Yinglingquan), GB34 (Yanglingquan), and EX-LE2 (Heding) acupoints on the lesion side (more painful side if bilateral), and the laser output device will be turned on for 10 minutes (830 group, 20 mW power; 650 group, 20 mW power; control group, 0 mW power). During the procedures, participants will be blindfolded, with no differences in sounds or feelings among the three groups

The STRICTA reporting guidelines, were designed to improve the completeness and transparency of reporting of interventions in controlled trials of acupuncture, in order that such trials may be more accurately interpreted and readily replicated [29]. STRICTA, Standards for Reporting Interventions in Clinical Trials of Acupuncture. Adapted from the article of MacPherson et al. (PLoS Med 2010;7:e1000261) [29]..

During treatment visits, all patients will be educated on exercise and self-care. Acetaminophen (500 mg) will be provided as rescue medication. At each visit, the medical conditions of the patients will be monitored to ensure compliance with the treatment and evaluation. The treatment and assessment schedule will be modified at the patient’s request or as deemed necessary by the researcher.

During the study, patients may take existing medications and receive treatments for other symptoms that do not influence the findings of the trial. However, they cannot receive other treatments to ameliorate KOA symptoms.

13. Outcome measures

1) Efficacy outcomes

The primary endpoint will be changes in VAS scores at rest and during activity (walking on a flat surface) 1 week after the last treatment (week 7). The secondary outcomes will include the Outcome Measures in Rheumatology Clinical Trials (OMERACT)-Osteoarthritis Research Society International (OARSI) sets of responder rates 1 week after the last treatment (week 7), patient global assessment (PGA), and doses of rescue medication at visit after six treatments (week 4), 1 week after the last treatment (week 7), and 6 weeks after the last treatment (week 12). Secondary outcomes will include changes in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total, WOMAC function subscale, WOMAC pain subscale, and European quality of life five-dimension five-level scale (EQ-5D-5L) at visit after six treatments (week 4), 1 week after the last treatment (week 7), and 6 weeks after the last treatment (week 12), and VAS at rest and during activity at visit after six treatments (week 4) and 6 weeks after the last treatment (week 12).

The VAS is a patient rating scale in which a 10 cm-long straight line is marked 100 for the worst pain imaginable and 0 for the absence of pain [30]. It is commonly used as a primary efficacy endpoint to assess pain intensity in clinical trials of KOA [19-22].

The OMERACT-OARSI set of responder criteria indicate high improvement in function or pain ≥ 50% and absolute change ≥ 20, or improvement in at least two of the following: 1) PGA ≥ 20% and absolute change ≥ 10, 2) function ≥ 20% and absolute change ≥ 10, and 3) pain ≥ 20% and absolute change ≥ 10 [31].

The WOMAC, a self-reported questionnaire, is commonly used in KOA and assesses pain, stiffness, and physical function. Each item is scored 0–4. Higher scores indicate increased stiffness, pain, and impaired physical function [32]. The PGA is a five-step measurement tool and is used to quantify disease improvement [33]. The EQ-5D-5L is used to assess health-related quality of life [34], and the quality weights of the EQ-5D-5L will be based on a previous study [35].

2) Safety outcome

Safety outcomes will be the incidence of AEs and changes in hematological test items (i.e., white blood cells, red blood cells, hemoglobin, hematocrit, platelets, and erythrocyte sedimentation rate), hematochemical test (i.e., alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, total protein, albumin, blood urea nitrogen, creatinine, glucose, gamma-glutamyl transferase, total bilirubin, sodium, chloride, potassium, and C-reactive protein), and urinalysis (i.e., specific gravity, pH, proteins, ketones, glucose, bilirubin, urobilinogen, nitrites, occult blood, leukocytes, and microscopic red blood cells and white blood cells), pulse rate, and blood pressure.

14. Adverse events

No AEs related to laser irradiation occurred in previous RCTs on KOA with LA [19,21] and in our pilot RCT on low back pain with ILA [25]. Possible AEs include pallor, dizziness, fainting, skin irritation, bleeding, and local hematoma. The CRC will record all SAEs and AEs, including the relationship between the intervention and AE, time of incidence, severity, and treatment procedures. All SAEs and AEs will be reported to the IRB and PI and monitored until stabilized. If intervention-related AEs and SAEs will occur, patients will be compensated in accordance with the applicable regulations.

15. Quality control

Experts in LA, statistics, methodology, and KOA have developed and reviewed the protocol. Investigators will receive training to understand the protocols and standard operating procedures (SOPs). To ensure that the trial complies with the protocol and SOPs, an independent clinical research associate will check all relevant documents. Any revisions to the protocol will be reviewed and approved by the IRB.

16. Sample size

We have not known previous or pilot studies from which the sample size could be calculated. Therefore, a pilot study design that considered the limited funds and study periods is adopted. The appropriate sample size for a three-arm pilot study is > 12 [36,37]. Assuming a maximum dropout rate of 20%, 45 participants (15 per group) will be included.

The findings of this study will provide preliminary data for the efficacy of ILA on KOA and will be used to calculate the sample size for rigorously designed RCT.

17. Statistical analysis

An independent statistician will analyze the final data using SAS^® version 9.4. A full analysis set will be used to assess efficacy, and missing values will be filled using the last observation carried forward method. The significance level is set to 5% (two-tailed). No sub- and interim analyses will be conducted.

To analyze changes in efficacy outcomes, the analysis of covariance, with the baseline score as a covariate, will be used for intergroup comparisons and the Friedman test or one-way repeated-measures analysis of variance for intragroup comparisons. The Bonferroni method will be utilized for significance-level correction in the post-hoc tests. The responder rate and incidence of AEs among the groups will be compared using Fisher’s exact test or chi-square test. To analyze changes in blood pressure, pulse rate, and blood chemistry parameters, the one-way analysis of variance or Kruskal-Wallis test will be used for intergroup comparisons.

18. Data management and confidentiality

All documents will be recorded and labeled using identification codes to conceal the names of the participants. All data will be securely kept in the myTrial data management system (NIKOM). Electronic data will be managed by a data management team, which has no conflicts of interest and is not affiliated with the sponsor. All data and identification records will be only accessible with IRB approval. Written informed consent for the dissemination of personal information will be obtained from all participants.

For LT to be effective in musculoskeletal disorders, sufficient energy must be delivered to the lesion [38]. Both high-intensity LT (HILT) and LLLT are effective in treating individuals with KOA. Compared with LLLT, HILT may be more effective in improving function and reducing pain in individuals with KOA because it penetrates deeper and works better on the deep structures of the knee joint as the power increases [39,40]. However, as LLLT is less expensive than HILT, it may be more suitable for both therapists and patients [39]. The absorption, reflection, and scattering of energy by the skin affect the transmission of LLLT energy. The transmittance rates of laser energy at 904 and 810 nm wavelengths in rat skin were 38–58% and 20%, respectively [41]. As the acupoints are located under the skin, low-energy penetration of the LA may not be effective enough to stimulate them [42]. Despite the low output power (20 mW), the ILA used in this trial could compensate for the scattering, absorption, and reflection of laser by the skin and deliver sufficient energy to the acupoints as light is emitted at the tip of the acupuncture needle inserted under the skin.

Clinical studies on LA for KOA with appropriate acupoint and laser parameters or methodologically high quality tend to show more significant and favorable effects on short- and long-term pain outcomes [22]. Wavelength, energy dose, number of sessions, and irradiation acupoints mainly affect the efficacy of LA for KOA [19,22]. The World Association of LASER Therapy (WALT) guideline recommends 904 or 780–860 nm for LLLT in patients with KOA [18]. In our previous pilot study, 650-nm ILA showed significant changes in the Oswestry Disability Index and VAS scores compared with sham lasers in individuals with chronic nonspecific low back pain [25]. Therefore, this study aims to explore the effects of 830- and 650-nm ILA on KOA. The WALT guideline recommends that 780–860-nm wavelength lasers (5–500 mW mean output, pulsed or continuous) for KOA should be irradiated with a 12 J/point energy dose (minimum 4 J/point) and daily treatment for 2 weeks (10 sessions in total) or every other day treatment for 3–4 weeks (9–12 sessions in total) [18]. In this study, the laser parameters will be a 12 J/point energy dose, 20 mW power, and pulsed type of wave. Moreover, the number of treatment sessions will be 12 (twice weekly for 6 weeks). The WALT guideline recommends that most of the pathological tissue in the synovia/tendon should be irradiated [18]. This study will choose EX-LE4 (Neixiyan), ST35 (Dubi), ST34 (Liangqiu), SP10 (Xuehai), SP9 (Yinglingquan), GB34 (Yanglingquan), and EX-LE2 (Heding) as the treatment sites, which are commonly used in clinical trials of acupuncture for KOA and are located around the knee joint [43].

In clinical studies of chronic pain, the recommended core outcomes include emotional functioning, physical functioning, pain, patient ratings of global improvement, participant disposition, symptoms, satisfaction with interventions, and AEs [44]. In this study, pain will be evaluated using the VAS, functional status will be measured using the WOMAC, satisfaction with intervention and patient ratings of global improvement will be assessed using the PGA, and symptoms and AEs will be assessed by the incidence of AEs.

This study has certain limitations. First, because of the limited recruitment opportunities and lack of appropriate previous research, a pilot study design is adopted. Second, various LA treatment methods for KOA could not be adopted. The treatment site and laser parameters are the main factors that affect the efficacy of LA for KOA [19,22]. Although various treatment acupoints and laser parameters have been used in clinical trials, this study will only compare the effects of two ILA wavelengths. Therefore, further studies are warranted to explore optimal treatment acupoints and laser parameters. Third, a double-blind study design will not be used. As the therapists will operate the medical device in accordance with the intervention protocol (830 and 650 groups, 20 mW; control group, 0 mW), and they know the group assignment.

Nevertheless, the findings of this study will provide clinical data regarding the optimal wavelength of ILA and its usefulness in KOA management, which will be adopted as the wavelength for ILA, and will provide the basis for the calculation of the appropriate sample size for future rigorously designed RCT.

We are grateful for the support of the investigators, participants, assessors, and statisticians involved in the study.

Conceptualization: JHK, CY. Data curation: CY, ARK, KMS. Formal analysis: BKK. Funding acquisition: JHK, CY. Investigation: JHK, JCS, RJ, GCP. Methodology: ARK, KMS. Project administration: JHK, CY. Resources: GCP, KMS. Software: ARK, KMS. Supervision: JHK, CY. Validation: JHK, CY. Visualization: CY, KMS. Writing – original draft: JHK, CY. Writing – review & editing: All authors.

The authors have no conflicts of interest to declare.

This research is supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health and Welfare, Republic of Korea (grant number: RS-2023-KH139215). The sponsor has no role in the study design and will have no role in data collection, analysis, interpretation, writing of the report, or the decision to submit the report for publication.

The study is conducted in accordance with the Declaration of Helsinki (revised in 2013). Protocol version 1.0 was approved by the Ministry of Food and Drug Safety (November 15, 2022; Medical Device Approval No. 1427). Version 1.1 was approved by the IRB of Dongshin University Gwangju Korean Medicine Hospital (July 18, 2023; Approval No. DSGOH-2023-002) and is registered with the Clinical Research Information Service (Registration No. KCT0008860). The principal investigator or a subinvestigator will explain the purpose and risk of this trial to the participants and their companions. All participants will provide written informed consent before participation.