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Introduction: Low-level laser therapy (LLLT) was introduced as an alternative non-invasive treatment for osteoarthritis, but its effectiveness is still controversial. The main objective of this article was to determine the safety and efficacy of LLLT in patients with knee osteoarthritis (KOA).
Methods: In order to gather evidence, main medical databases as well as relevant websites were browsed without time limit. We searched with appropriate keywords and strategies. After quality assessment of studies, study data were extracted by two reviewers. Standard mean difference proposed through inverse variance was used in the meta-analysis using the random-effects model. Twelve values were used for the evaluation of heterogeneity.
Results: A total of 823 studies, 14 randomized controlled trials (RCTs) were selected after final review. There was a significant difference between LLLT and placebo in pain at rest (P=0.02), pain at activity (P=0.01), total pain (P=0.03), WOMAC function (P=0.01), WOMAC stiffness (P=0.02) and WOMAC total (P<0.) in favor of the LLLT. There was no significant difference between LLLT and Placebo in WOMAC pain (P=0.09) and range of motion (P=0.1).
Conclusion: In spite of some positive findings, this meta-analysis lacked data on how LLLT effectiveness is affected with important factors: wavelength, energy density, treatment duration, numbers of sessions the treatment, severity of KOA and site of application
Keywords:
Knee, Osteoarthritis, Low level laser therapy, Effectiveness, Meta-analysis
Osteoarthritis is one of the most common diseases which has affected many people; this disease increases with age. In general, it may be said that approximately 14% of adults in United States and 40% of the population under 65 years old in Britain and Australia suffer from this disease; this disease prevalence is growing.1 Osteoarthritis is an example of physical and motor disability and one of the most important causes of functional disabilities in individuals, and imposes significant costs to individuals and consequently, to society.2 Knee osteoarthritis (KOA) is one of the most common osteoarthritis types and is associated with symptoms such as knee stiffness, pain, and limited movement range of knee joint. These conditions lead to physical function impairment, limited independence in doing daily life activities, decreased quality of life, and other disabilities.3,4
KOA is also known as arthritis or knee joint stiffness; it mainly affects the articular cartilage. The articular cartilage is a soft tissue which is inside the joint and between bones; in the case of its damage, the bones will rub on each other and extended bone will be created around the joint. Ultimately, the ligaments and muscles around the joint will be narrowed and weakened.1-4 There are several different treatments to control this disease (pharmacotherapy, surgery, physiotherapy, exercise therapy). It seems that the use of these methods depends on disease stage and patient's specific condition. In general, however, the logic and philosophy of these methods is relieving patient from pain, make him/her independent in doing daily life activities, and improving his/her life.5 Due to numerous complications which are associated with using non-steroidal drugs, using them to control this disease is limited.5 Recently, other therapies which are based on rehabilitation methods (such as exercise therapy, tensile muscle movement, electrical stimulation, acupuncture, and heat therapy) are more considered by physicians than using non-steroidal drugs.6 Low-level laser therapy (LLLT) is one of the safe and non-invasive methods which has recently attracted the attention of many researchers and specialists for treatment of KOA.7
Low-power laser therapy is a therapeutic approach which uses low intensity light-emitting in range of 540-830 nm light. It seems that the therapeutic effects of this procedure emerge by photochemical reactions which change permeability of cell membrane, increase build-up of mRNA, and lead to cell proliferation. The causes of these effects are not heat; like in surgery laser. The LLLT is used in many different diseases and mainly in pain control. Simply, it may be said that there are two types of lasers: low power and high power. The high-power lasers cut the tissue and release heat. However, the low-power lasers do not release heat and do not damage the tissue; they have the potential to produce photochemical reactions and improve the metabolism of cells. They are named low power lasers because they have a density of less than 5.0 W/cm2; they are also referred to as cold lasers or soft lasers. These lasers react in tissue and without causing heat, stimulate or inhibit the cells.8
After radiation of laser photons into cells, the cellular response begins with the activation of photoacceptors which are in the respiratory chain in mitochondria. Then, the cell redox and cell membrane state change, calcium displaces, pH changes, CAMP is activated, and DNA is dubbed; all of these lead to protein synthesis. In this way, the cellular responses extend from cell surface to tissue and organ surfaces and cause effects such as anti-inflammation, anti-edema and swelling, analgesia, cell proliferation, neovascularization and accelerated recovery, shifting metabolism to aerobic, and balancing immune system. In general, the physiological responses of tissue to low-power lasers include biological stimulation of system, effects on immune system, anti-inflammatory and anti-edema effects, effects on vessels and circulation, effects on lymph, effect on wound healing, analgesic effect, and effects on nerves.8 However, it seems that there are some uncertainties regarding the use of this therapeutic approach in people with KOA and the results of some studies are contradictory.9
Despite the broad clinical application of LLLT and also due to numerous randomized controlled trial (RCT) papers in terms of safety and efficacy of low power laser in people with KOA, the results of these articles are sometimes in contradiction with each other and its effectiveness is still in doubt. On the other hand, there are few systematic and meta-analyses studies that clarify the efficacy and safety of LLLT in these patients. The last systematic study that has been conducted in this area in recent years belongs to Huang et al.10 However, the study does not encompass some related articles, does not consider follow-up period of outcomes in the analysis and does not analyze consequences such as pain at rest, pain during activities and quality of life. Accordingly, we aimed to alleviate some of these limitations, to have a more comprehensive analysis of the safety and effectiveness of low power laser in people with KOA and ultimately contribute to an evidence-based decision making and policy on the use of this technology in this group of patients.
This study conforms to all PRISMA guidelines and reports the required information accordingly. We performed a systematic review of best evidence using Cochrane guidelines. Our structured question for this review was as follows in Box 1.
Population: People with KOA;
Intervention: Low-level(power) laser therapy;
Comparator: Placebo Laser Therapy;
Outcome: Pain relief, activity, range of motion, adverse side effects;
Type of studies: RCTs and observational studies
We searched the most important and appropriate electronic medical databases including MEDLINE, PubMed, Cochrane library, Science Direct, Trip, Google Scholar, Thomson Reuters (formerly ISI) Web of Knowledge, SCOPUS and EMBASE as well as relevant websites were browsed without time constraint up to September . The Me SH system was used, as well as 'AND' and 'OR' between words of the same meaning and concept i.e. Low Level, Low Power, Laser Therapy, LLLT, LPLL, osteoarthritis and knee. The collected papers were organized in Endnote software. After deleting duplicate articles, 2 reviewers independently assessed the titles and abstracts of the search results and selected potentially relevant studies according to our main question (Box 1). The articles that were deemed to be irrelevant to the research objectives were excluded. After collecting the full texts of articles which were related to the objectives of this study, the references of these articles were reviewed. The related references were identified and their full texts were reviewed. All stages of obtaining evidence and selecting studies were independently conducted by 2 authors. The disputes between them were resolved by discussion and by third party, if needed.
The inclusion criteria included (1) clinical trials articles, (2) people with KOA who were identified and approved by American College of Rheumatology indices, (3) the articles which compared low-power and LLLT with placebo laser, (4) articles which examined consequences such as pain, stiffness, performance, activity, and quality of life, and (5) articles which were published in English or Persian. The exclusion criteria included (1) fundamental research or studies on animals, (2) review articles, (3) articles which had not related statistical and clinical data, (4) articles which used LLLT or placebo laser along with another intervention, (5) duplicate articles which had up-to-date versions. Since the full text of all articles was available and we managed to get all of full articles, none of them was excluded.
The Cochrane's Paper Quality Assessment Checklist was used to evaluate the quality of articles; this process was carried out independently by 2 authors and the disputes between them were resolved by discussion and by third party, if needed. Since this tool evaluates 7 aspects of bias risk, therefore, a 10-point scale was considered for article quality: scores above 7 indicate high quality, scores between 5 and 7 indicate medium quality of paper, and scores less than 5 indicate low quality of article. In dimensions 1 to 6, in general, the articles with low bias risk scored 1.5, the obscure bias risk scored 0.75, and the articles with high bias risk scored 0. In seventh dimension, the low bias risk scored 1, the obscure bias risk scored 0.5, and the high bias risk scored 0.
A special form was created in Excel to extract data from final articles. The needed data including general information (including title of article, year of publication, country, corresponding author) and specific information (including population size, sample size, type of study, statistical data related to each outcome, outcome follow-up time, and other useful information) were collected by 2 authors independently. After completing the forms, the disputes between them were resolved by discussion and by third party, if needed. In cases where the article information was incomplete and specific information about article was needed, the corresponding author was called and in the case of cooperation, necessary information was taken.
Since the data of studied outcomes were continuous, the mean difference or standardized mean difference and reverse variance method were used to pollute these data. The Fix model was the statistical model which was used in the first step. However, in cases where there was high heterogeneity between studies, a randomized model was used. The chi-square and I² statistics were used for evaluating heterogeneity. The I2 more than or equal to 40% indicated high heterogeneity and less than this value indicated negligible heterogeneity.12 In all tests, the significant level was considered to be 0.05 (95% CI). The meta-analysis was performed using RevMan software, version 3.1.
According to the World Health Organization's Functioning, Disability, and Health Classification model (ICF), the disability is the result of action-reaction between health conditions, environmental factors, and personal factors. According to this model, the disability results from damage in anatomical structure and physiological function of body, and limitations in activity and participation. The environmental and personal factors may play deterrent or facilitator role to affect the disabilities. KOA damages the structure and the physiological function of the knee joint. This damage may result in pain, functioning difficulties in daily living activities, and limited participation in living levels. On the other hand, environmental and personal barriers may increase the disability. LLLT has been introduced as a non-invasive therapeutic intervention for skeletal muscle disorders especially joint osteoarthritis during the past two decades. In spite of the widespread use of LLLT in KOA patients and also multiple trials in this area, there are inconsistent results regarding this technology efficacy. Stelian and colleagues'23 research in was the first trial of laser effectiveness compared to placebo laser in KOA patients. The results of this trial showed improved function and pain reduction outcomes in patients who received laser treatment. After this trial, the studies conducted in the following years including Bulow et al30 and Tascioglu et al24 did not confirm the efficacy of LLLT compared to placebo laser. There were no significant differences between 2 groups in terms of performance improvement, pain relief and other clinical outcomes in these two studies.24,30 The efficacy of LLLT in KOA patients remains unknown due to these conflicting results. In spite of numerous clinical trials on LLLT efficacy in patients with KOA, there are few systematic and meta-analysis studies that clarify the LLLT efficacy and safety. This systematic and meta-analysis study was conducted based on the Cochrane Institute's guide. After reviewing titles, abstracts and full texts of 823 articles, 14 randomized clinical trials were randomly selected for analysis, of which, 9, 2 and 3 were of high, moderate, and low levels of quality, respectively. Total patients of LLLT group were 350 and total patients of placebo group were 328. All outcomes that were analyzed were continuous. Therefore, data were pooled using random effect model and statistical inverse variance method and the standardized mean difference, which was statistically significant at the 5% level. The results of the meta-analysis on pain at rest, pain during activity, general pain, WOMAC function, WOMAC stiffness and overall WOMAC outcomes showed significant differences in favor of LLLT, but there were no statistically differences between the 2 groups in WOMAC knee pain and range of motion outcomes. There is insufficient evidence to draw any firm conclusions regarding the use of laser for the treatment of KOA. However, no side effects were reported and no evidence of harm was found.
Results of Huang and colleagues'10 meta-analysis did not show significant differences between two groups in overall pain outcomes, but our meta-analysis suggests a significant pain reduction in patients who received LLLT. Huang meta-analysis also showed no significant differences between two groups in WOMAC stiffness and WOMAC functional outcomes, while our meta-analysis indicated a significant improvement in patients who received LLLT. The results of our meta-analysis were similar to Huang and colleagues' study10 concerning WOMAC pain and range of knee motion outcomes in which there were no significant differences between two groups.
Since there was a significant heterogeneity in results of outcome meta-analysis, it cannot be said with certainty that the LLLT impacts in reducing pain and improving function in patients with KOA.
The use of different wavelengths, treatment times, number of sessions, and adjuvant therapy such as physical therapy along with LLLT, attrition during follow-up periods, illness severity, energy density and laser continuous output are the most important factors that affect the efficacy of Low Power Laser in patients with KOA. It seems that differences in these parameters are causing heterogeneity in the meta-analysis results. The wavelengths used in the entered trials was between 830 to 904 nm and the energy density was between 0.76 to 50 J/cm² as well as laser output varied between 4 to 800 mW. It seems that the differences in wavelength, laser output and energy density in the entered trials may result in heterogeneity. The total numbers of treatment sessions in the underlying trials were between 8 to 20 sessions and the length of treatment times varied between 6 and 160 minutes and this probably caused the different results of the LLLT efficacy. On the other hand, if the illness severity is mild, treatment effectiveness will be more evident. So LLLT do not have enough effectiveness for severe cases. It seems that the application of LLLT combined with other methods such as physical exercises leads to better clinical outcomes. Most attrition during follow-up periods were related to studies of Shen et al22 (13 cases), Hinman et al19 (32 cases), Kheshie et al20 (7 cases) and Alfredo et al13 (6 cases). Reduced sample size may lead to biased results in these trials.
The last systematic study in this area in recent years belongs to Huang et al.10 However, the study neither encompasses some related articles, nor considers follow-up period of outcomes in the analysis, it also does not analyze consequences such as pain at rest, pain during activities and quality of life. The most important limitation of this study is, of course, high heterogeneity between studies that is the reason for using random model for meta-analysis. Moreover, another limitation of this study is small sample size in each paper and generally low sample size of outcomes which were analyzed. Three articles in reviewing of pain outcome, 2 articles in reviewing of activity outcome and 3 articles in reviewing of motion range reported just the mean without standard deviation and exact P value. We tried to make contact with the corresponding authors of these trials. Unfortunately, we did not get any response. Incomplete statistical data caused data exclusion from analysis and this may affect the results.
The results of our systematic review and meta-analysis have provided the best current evidence on LLLT in the treatment of KOA. Although the heterogeneity of the results calls for caution in interpretation, LLLT seemed to be effective in reducing pain and improving function in patients with KOA. In spite of some positive findings, this meta-analysis lacked data on how LLLT effectiveness is affected with important factors: wavelength, energy density, continuous laser output, treatment duration, number of treatment sessions, lost to follow-up, severity of KOA and site of application.
Not applicable.
The authors have no conflict of interests relevant to this article to disclose.
The authors would like to thank the following individuals who have contributed at various stages through the development of this project.
Please cite this article as follows: Rayegani SM, Raeissadat SA, Heidari S, Moradi-Joo M. Safety and effectiveness of low-level laser therapy in patients with knee osteoarthritis: a systematic review and meta-analysis. J Lasers Med Sci. ;8(Suppl 1):S12-S19. doi:10./jlms..s3.
Our primary technology are Class IV infrared therapy lasers. Class IV lasers gently warm the problem area while delivering infrared laser energy, decreasing pain and inflammation, and often improving healing times.
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No, treatment with Class IV laser therapy is not painful. You'll experience a gentle warming sensation over the treatment area. Occasionally patients experience other mild sensations of healing, like itching and tingling on the surface of the skin.
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No, you don't need to remove your clothing to receive Class IV laser therapy.
Only the skin over the treatment area needs to be uncovered. In most cases, clothing can be moved or pushed aside from the treatment area. In some cases athletic shorts and sleeveless tops are helpful for reaching the treatment area.
Any treatment directed near sensitive areas will be properly draped to respect privacy.
With competitive price and timely delivery, Easetak sincerely hope to be your supplier and partner.
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The length of your treatment depends on:
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We offer competitive rates for high powered laser therapy. Total costs depends on your particular health concern and treatment needs.
Insurance may offer reimbursement for Class IV laser therapy in cases of personal and auto injury.
Despite decades of use in Europe, and 13+ years of use in the US, most commercial insurances are not reimbursing for laser therapy at this time.
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Cold laser is a different laser technology than Class IV lasers.
We use Class IV infrared therapeutic lasers. These are sometimes called deep tissue or high powered lasers as opposed to cold laser.
There are benefits to both kinds of laser, but we have chosen Class IV lasers because of the advantages this kind of laser offers.
Cold lasers use less power.
Cold lasers use less power than high powered lasers. Cold lasers are Class III lasers, which are rated at a 1/2 watt of energy and below. Since, they use less energy Class III lasers are called 'cold' and sometimes 'low level light therapy.'
(Technically only a certain kind of Class III laser is considered a cold laser, but the name is used for nearly all Class III lasers.)
Class IV lasers use 1 watt to up to 60+ watts of energy. However most pain-relieving lasers are set between 1 and 15 watts.
Class IV lasers and have many different uses depending on the laser aperture or tool. For example, dental and minor cosmetic surgery is possible with the lasers used in our offices. The lasers you'll experience are fitted with a therapeutic head, and not a surgical head.
The power is used to penetrate the tissue to help deliver infrared laser to encourage pain relief and healing.
Most patients are not concerned with the difference between laser types. In fact, most aren't aware there are differences in laser technology and most are still happy with their treatment.
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This is a technical question that doesn't interest all patients. However, every once and someone wants to know the overall differences between Class III and Class IV lasers.
Here are the major differences:
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Yes, lasers are regulated by the FDA. The conditions and source of pain found on this website are cleared by FDA for laser treatment. The first lasers cleared for human use were approved in . Class IV lasers began their clearance in .
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We have those conditions listed on our laser conditions page. If you have a question about a condition, you can always use our contact form or call our number to ask any questions.
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The short and non-technical answer:
Class IV lasers decrease tissue inflammation and reduce pain. In some ways, it is like getting the best of ice and heat at the same time.
But the technology does more than that.
Lasers can also accelerate a healing response in the body by providing light energy to stressed and damaged cells.
Here is the longer, and more technical answer:
Laser is an acronym. It means 'Light Amplification by the Stimulated Emission of Radiation.'
Therapeutic lasers delivers a beam of light from the red or infrared light spectrum. Red lasers are visible to the naked eye, but infrared is outside the spectrum of visible light and cannot be seen.
(Infrared light from Class IV lasers require the use of special safety glasses to protect the retina. All our providers use these glasses.)
The red or infrared light is delivered at a single wavelength and is absorbed by the body. Individual cells absorb the red and infrared light and the energy centers of the cells are activated.
Lasers stimulate cells to heal:
There are several known effects from consistent laser treatment:
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