Effectiveness and Potential Benefits of the Use of Laser Light Therapy in Musculoskeletal Rehabilitation Programs for Knee Osteoarthritis: A Narrative Review

1. Introduction

Osteoarthritis (OA) is a chronic disease with increasing prevalence as people get older and is common among the elderly population aged over 65 years [1]. It is associated with reduced functional activity and disability, the pathophysiology of which is based on primary damage of the cartilage and all structures functionally related with joint movement: bones, muscles, joint capsule, including peripheral nerves and altered proprioception [2,3,4].

In recent years, the prevalence of OA has been increasing worldwide. This trend has become a significant burden both for the healthcare system as a whole and for the affected individuals, who live with the symptoms of the disease for many years [5,6]. OA is a degenerative joint disease closely associated with increased mechanical stress on the joints, obesity, gender, hormonal imbalance, age, and a history of trauma. Chronic pain and reduced functional activity require long-term treatment, which is accompanied by increased healthcare costs [7].

OA is a long-term condition; it may start without symptoms, but the disease can subsequently progress into a chronic joint disorder. Patients often report pain that ultimately leads to difficulty performing daily activities and permanent damage [8,9,10]. Most commonly, OA affects the large weight-bearing joints of the lower extremities: knees, hips, as well as the hands, spine, and others; and in fact, it can affect any joint in the body. In some patients, OA may remain clinically silent for a long time and present as an asymptomatic form of OA. Nevertheless, the process of joint damage leads to advanced changes in the cartilage, subchondral bone, and surrounding muscles. Symptomatic OA manifests clinically with symptoms such as pain, stiffness, swelling, limited range of motion, crepitus, and muscle weakness. The prolonged persistence of these symptoms leads to reduced physical activity, and this, in turn, exacerbates the symptoms of OA [11] and lowers patients’ quality of life [12]. There are many factors that play a significant role in the pathogenesis of OA, and the aging of the body’s structures and tissues must also be included among them. This also applies to cartilage cells, the chondrocytes. Furthermore, OA is characterized by low-grade inflammation, which is due to the production of cytokines (interleukin-1β (IL-1β), tumor necrosis factor (TNF), and interleukin-6 (IL-6)) [13,14]. Pathological changes in lipid metabolism may also contribute to the development of a chronic inflammatory process that accelerates the progression of OA [15]. The progression of the degenerative process may also be a result of impaired regenerative capacity of cartilage, synovial, and subchondral bone cells following injury [6,16].

The OA management strategy and the associated pharmacological therapy have made undeniable progress; however, the prevalence of OA has been increasing in recent years. Very often, long-term medical treatment is associated with increased risk of adverse reactions [17].

Incorporating non-pharmacological treatments is of great importance for reducing patient suffering. Physical medicine factors may be a suitable alternative for slowing the progression and managing the symptoms of OA, as more and more evidence accumulates in this regard. The American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR) recommend incorporating appropriate physical activity. Therapeutic exercises performed regularly can reduce pain and, as a result, have a beneficial effect on the symptoms of OA. Other suitable therapies with varying degrees of evidence include: manual therapy, assistive devices, orthoses, thermotherapy and cryotherapy, TENS, magnetic fields, ultrasound, and laser therapy, which has also been discussed recently [18].

Currently, laser therapy is a frequently used therapeutic method for alleviating symptoms of musculoskeletal disorders in clinical practice [19]. A number of benefits from the use of low-intensity lasers (Class III) have been reported in recent years [20]. At the same time, this method, which uses a low-energy laser, is subject to a number of factors that limit its effectiveness, such as penetration depth and the amount of energy delivered to the deeper layers of tissue structures. These limitations can be overcome by using more advanced Class IV lasers, which are considered high-energy lasers.

The therapeutic effect of low-energy lasers is based on the ability of cells to absorb light through so-called chromophores. This process is known as photobiomodulation. The most commonly used light is from the red and near-infrared spectrum (typically between 600 nm and 1100 nm). This light spectrum leads to increased production of mitochondrial ATP, improved cellular signaling and synthesis of growth factors, as well as reduced levels of oxidative stress [21].

Unlike low-level lasers (LLLT), the biological effects of high-intensity lasers (HILT) are based less on the absorption of chromophores and more on photochemical interactions and the photobiostimulation effects on tissues. Photochemical reactions are associated with the acceleration of oxidative processes in the mitochondria, the production of energy substrates in the form of adenosine triphosphate, and the synthesis of DNA and RNA. The advantage of high-energy lasers over low-energy ones is that they can reach deeper structures within larger joints. Through their deep thermal effect, high-intensity lasers cause an increase in local blood circulation and improve tissue regeneration, while at the same time reducing pain and swelling [22].

The aim of this review is to provide an overview of the literature and the current possibilities for using laser light (low-intensity and high-intensity laser therapy) in musculoskeletal rehabilitation programs for knee osteoarthritis.

2. Materials and Methods

A narrative review of the scientific literature published in accessible databases (PubMed, ScienceDirect, Google Scholar, ResearchGate) was conducted. A search was conducted in these databases for scientific articles containing information on the use, efficacy, and benefits of laser light (low-intensity laser therapy (LLLT) and high-intensity laser therapy (HILT)) in musculoskeletal rehabilitation programs for knee osteoarthritis. The following terms were used for the search: “laser therapy” OR “low-intensity laser therapy” AND “LLLT,” OR “high-intensity laser therapy” AND “HILT” AND “knee osteoarthritis,” OR “photobiomodulation” AND osteoarthritis, “musculoskeletal rehabilitation” AND “pain” AND “functional activity” OR “activities of daily living.” This narrative review includes articles published from January 2000 to June 2026. The inclusion criteria covered full-text publications in English and Bulgarian containing data in which the primary therapeutic factor was laser light (LLLT and/or HILT). In accordance with these criteria, the following were included: observational scientific studies, randomized controlled clinical trials, systematic reviews, and meta-analyses. The following were excluded: letters to the editor, case reports, abstracts from articles or conferences, duplicate articles, or those for which full-text access was not available or that did not meet the inclusion criteria.

3. Results

This section may be divided by subheadings. It should provide a concise and precise description of the experimental results, their interpretation, and the experimental conclusions that can be drawn.

Data were found indicating a high rate of permanent disability due to musculoskeletal disorders, particularly osteoarthritis, in elderly patients. This calls for optimizing existing strategies for managing osteoarthritis and seeking non-pharmacological alternatives that can be safely and reliably incorporated into treatment plans. The rehabilitation process needs to cover all stages of osteoarthritis progression. Furthermore, it should incorporate various therapeutic approaches depending on the disease stage and activity level and its impact on pain, functional activity, and independence in performing daily living activities. At the same time, evidence of varying levels of significance has been found regarding the positive effects of LLLT and/or HILT (alone or in combination with other physical modalities) on the sustained reduction of osteoarthritis symptoms.

3.1. Low-Level Lasers (LLLT)

With regard to the use of LLLT in rehabilitation programs for osteoarthritis, there is a number of studies showing a reduction in pain and an improvement in joint function compared to placebo-LLLT [23]. Positive results have also been reported regarding gait (increased walking speed and improved parameters such as stride length and stability) [24]. Improvements in functional activity and stiffness (most commonly assessed using the WOMAC scale) have also been reported [23,24,25,26,27,28,29,30].

According to some studies, better results with long-lasting effects are achieved when LLLT is used in combination with physical exercise. LLLT is applied as a preparatory or adjunctive procedure prior to kinesiotherapy, strength training [26,27], or stretching exercises [29]. Laser therapy reduces inflammation and pain, allowing patients to perform exercises more actively and effectively. Some studies report that the therapeutic effects of rehabilitation with LLLT combined with exercise last for as long as 6–12 months after the completion of the treatment course. Long-term or repeated application of the therapy helps maintain the functional capacity achieved [25,26]. On the contrary, however, another randomized trial reports that LLLT photobiomodulation does not provide an additive effect when patients are already following an exercise program to strengthen their muscles [31]. Some review reports point out that clinical success depends on compliance with the internationally recognized recommendations issued by the World Association for Photobiomodulation Therapy (WALT). The use of an optimal wavelength (most commonly in the infrared spectrum: 808–904 nm) and the therapeutic energy dose of the laser spot are crucial for achieving a therapeutic effect [23,30].

It is noteworthy that there is conflicting evidence and discrepancies in the findings of some of the meta-analyses. Positive results are reported in a meta-analysis conducted by Stausholm et al. (2019) and in individual randomized controlled trials (RCTs), which report clinically significant reductions in pain and disability when the doses recommended by WALT (particularly 808–904 nm) are administered in combination with exercise. On the other hand, some meta-analyses (Huang et al. (2015) and Brosseau et al., 2004) [32,33], as well as the clinical trials by Tascioglu et al. (2004), Jorge et al. (2023), and Rastgar Koutenaei et al. (2017) [31,34,35]. Rastgar Koutenaei F. et al. (2017) found that LLLT does not provide any additional benefit over a placebo or a standard exercise program [35]. In other studies, not directly related to OA, Tomazoni et al. (2020) investigated photobiomodulation for nonspecific low back pain and reported no reduction in pain or disability compared to placebo, suggesting that the effects of the therapy cannot be easily extrapolated across different musculoskeletal conditions [36]. The results regarding the potential therapeutic benefits of LLLT are summarized in Table 1.

3.2. High-Intensity Laser Therapy (HILT)

High-Intensity Laser Therapy (HILT) has recently been increasingly incorporated into rehabilitation protocols for osteoarthritis (OA) and a number of associated musculoskeletal conditions, as one of the most promising modern noninvasive physical therapy modalities. Unlike low-intensity laser therapy (LLLT), HILT is characterized by high peak power (reaching 1–12 W or more) and a specific wavelength (most commonly 1064 nm [Nd:YAG laser]), as well as high-power diode systems (810/980/1064 nm).

Evidence of a statistically and clinically significant reduction in pain compared to placebo treatments has been found for HILT, LLLT, and physical therapy alone in a number of studies [37,38,39,40,41] as well as in systematic reviews and meta-analyses (Ahmad et al., 2022; Cai et al., 2023; Wu et al., 2022) [42,43,44]. The analgesic effect manifests early, as early as after the first 3–5 sessions, with improvement observed [37,45]. In addition, improvements in joint function and stiffness, as measured by the WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) and the Lequesne Index, have been reported. There is evidence that HILT has a positive effect on morning stiffness and functional capacity [37,38,39,41,44].

Recent evidence suggests that HILT may affect cartilage thickness, muscle strength, and range of motion. In a pilot study, Ekici B, Ordahan B. (2023) using ultrasonography to assess femoral cartilage thickness, found that HILT treatment led not only to a significant increase in quadriceps femoris muscle strength and range of motion (ROM), but also to a statistically significant increase in femoral cartilage thickness [41]. This suggests the need for future studies to investigate the potential of HILT to have a chondroprotective and anabolic effect on articular cartilage.

Evidence has been found that HILT is more effective than LLLT in treating osteoarthritis. This is likely due to the fact that HILT penetrates deeper into the tissues, resulting in faster and longer-lasting pain relief compared to LLLT [42,46]. According to the results of other studies, HILT has been found to be more effective in rehabilitation programs than low-intensity pulsed ultrasound (LIPUS) and TENS in terms of duration of the analgesic effect and improvement in functional indexes [39,47]. A number of studies report better results achieved by combining HILT with therapeutic exercise programs [39,40,42].

When searching for scientific evidence regarding the potential benefits of HILT therapy, it was found that this therapeutic modality may also be effective for other degenerative and inflammatory conditions such as chronic low back pain and/or cervical discopathy [47,48,49], carpal tunnel syndrome [50,51], tendinopathies, and temporomandibular disorders [52,53]

Although scientific studies on potential therapeutic effects of HILT in osteoarthritis (particularly in the knee joint) show predominantly positive results, there are nevertheless clinical studies that report a lack of effect and/or a lack of a statistically significant difference compared to the placebo group or other conservative therapies. These clinical trials generally note that, although HILT may lead to short-term pain relief in individual sessions, it does not outperform placebo therapy or standard exercises in terms of functional improvement (WOMAC scale), stiffness, muscle strength, or proprioception [54,55,56]. The findings regarding the potential therapeutic benefits of LLLT are summarized in Table 2.

Studies give preference to high-intensity laser therapy, but there are also some that highlight the therapeutic potential of low-intensity laser therapy. However, at this stage, no strict recommendations have been adopted regarding the inclusion of LLLT and/or HILT in musculoskeletal rehabilitation programs for osteoarthritis. These findings highlight the need for further research, and development of standardized protocols for laser therapy application (LLLT and HILT).

4. Discussion

Osteoarthritis is one of the most common forms of musculoskeletal disorders, associated with permanent disability and a reduced quality of life in elderly people [59]. The reduced daily activity and psycho-emotional stress observed in osteoarthritis (OA) patients are a result of chronic pain, increased muscle imbalance, reduced joint mobility, and gait problems [60]. According to current recommendations, these symptoms can be managed through preventive measures such as proper nutrition, regular physical activity, maintaining and increasing muscle mass and strength, and maintaining a normal weight without obesity [18]. The next step in the treatment plan for patients with OA is the use of pharmacological agents, although a number of pain-relieving medications and nonsteroidal anti-inflammatory drugs (NSAIDs) may cause various adverse side effects. Once all other options for managing OA symptoms have been exhausted, patients are offered surgical treatment involving replacement of the joint damaged by degeneration. This type of definitive treatment makes it possible to overcome pain and improve patients’ mobility [62]. However, this treatment is associated with significant financial expenses resulting from the surgical procedure and the need for postoperative rehabilitation and recovery [7].

On the other hand, OA develops slowly over the course of years. This requires preventive care, prophylaxis, and both pharmacological and non-pharmacological treatment. Recently, increasing attention has been paid to non-pharmacological treatment options due to their low incidence of side effects and ease of application. Physical medicine offers a suitable alternative to drug therapy, particularly for patients with subacute and chronic pain associated with OA.

4.1. Low-Energy Laser Therapy

Along with exercise programs, lifestyle changes, and increased physical activity, low-energy laser treatment can be an effective pain-relieving tool. In rehabilitation programs, low-energy laser therapy with a wavelength of 785–904 nm is often combined with therapeutic exercises. As a result of this combined therapy, a reduction in pain, an improvement in the range of motion of the affected joint, and an improvement in functional status—as measured by the WOMAC Index [30]—are observed. In a systematic review and meta-analysis, Stausholm MB. et al. (2019) found that low-intensity laser therapy with wavelengths of 785–860 nm and 904 nm can significantly reduce pain and disability in patients with knee OA [23]. According to some studies, low-energy laser therapy (wavelength 904 nm) combined with a program of strengthening exercises administered for 8 weeks can significantly reduce daily paracetamol use [25]. Another randomized study examining the effect of low-intensity laser therapy (808 nm), combined with physical exercise, showed good results as measured by the WOMAC Index, as well as improved unilateral balance when standing on one leg in patients with bilateral knee osteoarthritis [24]. Stausholm MB. et al. (2022), in a controlled, randomized clinical trial of the use of a low-energy laser (904 nm) in combination with strength training, found a positive effect on pain and reduced use of analgesics in patients with knee osteoarthritis [27]. In another randomized controlled clinical trial using a low-energy laser with a wavelength of 850 nm, the authors reported a reduction in pain, as well as improvements in range of motion and function in patients with knee osteoarthritis [28]. In a recent study, Robbins et al. (2022) reported that a rehabilitation program incorporating low-intensity laser therapy (904 nm) and therapeutic stretching exercises significantly reduced pain at rest and stiffness, and improved range of motion and daily activity in patients with hip osteoarthritis [29]. In another recent study, it was reported that a 3-week course of low-intensity laser therapy as monotherapy led to a reduction in knee pain and disability, as assessed by the Lequesne scale in the first phase of the study. In the second phase of the clinical trial, combined low-intensity laser therapy and therapeutic exercises were administered for 8 weeks, resulting in reduced pain medication intake, improved mobility, range of motion, muscle strength, and daily functional activity, as assessed by the WOMAC (Western Ontario and McMaster Universities Osteoarthritis Questionnaire) over a 6-month period [26].

On the other hand, there are clinical trials that do not find a significant effect of low-intensity laser therapy in patients with OA. In reported study data from Jorge et al. (2023), no significant difference was found in pain, physical function, and quality of life between the group receiving combined therapy with strengthening exercises and low-intensity laser therapy and the group receiving placebo laser therapy and exercises [31]. Tomazoni SS. et al. (2020) found no reduction in pain or disability in patients with low back pain [36]. Huang Z et al. (2015) reported a lack of evidence regarding pain reduction (measured on a visual analog scale (VAS)), both immediately after therapy and twelve weeks later. They also found no difference in the WOMAC subscales for stiffness and function between low-intensity laser therapy and placebo in patients with knee osteoarthritis [32]. In another, earlier review, Brosseau L. et al. (2004) reported conflicting data on the effect of low-energy laser therapy compared to placebo therapy. However, the authors point out that the results may have been influenced by a number of methodological shortcomings in the studies, the dosage of laser therapy, and other factors [33]. The differences in the conclusions between the meta-analysis by Stausholm MB. et al. (2019) [23] and those by Huang et al. (2015) [32] are likely attributable to the methodology of study selection and dosimetric criteria used. This possible cause likely led to the conflicting conclusions regarding the therapeutic effects resulting from applying the same treatment. While Stausholm MB. et al. (2019) (22 studies (1,063 patients)) assessed the laser’s efficacy on the basis of compliance with internationally established WALT dosage recommendations, Huang et al. (2015) (9 studies, 518 patients) pooled all studies, regardless of whether the administered doses were therapeutic or too low. The World Association for Photobiomodulation Therapy (WALT) has currently developed and approved official guidelines and standards for LLLT dosing in the treatment of osteoarthritis (for example, for knee OA, which is considered a deep-seated joint; WALT recommends that the dose be calculated for each individual anatomical application point (J/point) on the joint space, rather than as a total amount applied to the entire knee).

Due to the lack of sufficiently convincing evidence regarding its therapeutic effects and advantages over other physical modalities, low-intensity laser therapy is not currently included in the recommendations of the OARSI (Osteoarthritis Research Society International), the ACR (American College of Rheumatology), and EULAR as a primary or mandatory treatment for osteoarthritis. High-quality studies must continue to be conducted in order to reliably demonstrate the therapeutic efficacy of low-intensity laser therapy.

4.2. High-Intensity Laser Therapy

In recent years, high-intensity laser therapy has become increasingly widespread in clinical practice as a treatment for managing symptoms of degenerative musculoskeletal disorders [42]. It has the advantage of being a non-invasive method capable of penetrating up to 100 mm into the target tissues [43]. The effectiveness of this therapy derives from the fact that the high-energy laser enhances reparative processes in connective tissue. This process is based on the ability to improve fibroblast function, influence the secretion of anti-inflammatory substances and endogenous mediators by suppressing pro-inflammatory cytokines (IL-1β, IL-6, TNF) and by increasing the secretion of serotonin and β-endorphins, which leads to the normalization of neuronal excitability and, consequently, to effective pain relief [26], as well as to improved tissue metabolism [46]. On the other hand, according to some researchers, high-intensity laser has the ability to activate the regeneration processes of peripheral nerve fibers, which may provide another possible explanation for the mechanism of pain reduction through its effect on the “pain-gate control” system [57]. Pain relief is also achieved by reducing the effects of inflammation by suppressing the activity of cyclooxygenase and lipoxygenase. As a result of the effect on these enzymes, the production of prostaglandins and prostacyclins is reduced, leading to decreased inflammatory response and associated exudation and proliferation [37,43].

A placebo-controlled randomized trial reported favorable outcomes from high-intensity laser therapy compared to the placebo group in terms of pain (measured using the VAS and dolorimetry) in patients with knee OA. The authors suggest that the effect of the therapy is cumulative following a series of seven sessions [37]. In another double-blind, randomized, placebo-controlled study, Akaltun MS. et al. compared the effects of high-intensity laser therapy and therapeutic exercises in the experimental group with those of placebo laser and therapeutic exercises in the control group. Patients received a total of ten sessions over two weeks. Upon completion of therapy, a statistically significant improvement was observed in pain (VAS), functional activity (WOMAC Index), and range of flexion. Ultrasonography revealed a positive change in femoral cartilage thickness in both groups. Six weeks after therapy, better results were observed in terms of reductions in VAS and WOMAC scores, as well as increased mobility and cartilage thickness, in the group receiving therapeutic laser and exercises compared to the group receiving placebo laser and therapeutic exercises [38].

A statistically significant reduction in pain with high-intensity laser therapy compared to the control group for lower back pain, as well as a positive effect on disability indexes (the Oswestry Disability Index and the Roland Disability Index), is reported in a systematic review and meta-analysis by Abdildin Y. et al. (2023) [48]. Another meta-analysis also found evidence that high-intensity laser therapy in patients with back and neck pain leads to a significant improvement in pain and disability scores compared to control groups [58].

Some of the studies analyze the results of trials comparing the effects of high-intensity laser therapy with other electrotherapeutic modalities. In a randomized controlled trial, Gocevska M. et al. (2019) found that high-intensity laser therapy combined with exercise yielded better results compared to the control group (ultrasound therapy and exercise) in patients with lower back pain. The results were evaluated using the Numeric Rating Scale for Pain (NRSP), the Oswestry Disability Index, and Schober’s test. The researchers reported a significant reduction in lower back pain and disability, as well improved range of motion. The positive effect persisted for three months [49].

Samaan SS. et al. (2022) conducted a randomized controlled trial to study high-intensity laser therapy impact combined with therapeutic exercises (focused on range of motion, muscle strengthening, and flexibility), compared to therapeutic ultrasound combined with exercises and therapeutic exercises alone. They found that high-intensity laser therapy combined with therapeutic exercises is significantly more effective in reducing pain, improving knee range of motion, and may result in reduced functional impairment and improved proprioceptive accuracy compared to low-intensity therapeutic ultrasound combined with exercises. However, on the other hand, both high-intensity laser therapy and therapeutic ultrasound combined with exercises achieve better results than a complex of therapeutic exercises alone [39]. In another study, Nazari A. et al. (2019) compared the effects of high-intensity laser therapy with routine therapy using TENS and therapeutic ultrasound. They reported that high-intensity laser therapy, administered over four weeks at a rate of three sessions per week, outperformed routine treatment and achieved better results in terms of pain reduction and improvement in functional activity (range of motion, Timed Up and Go (TUG) test, 6-Minute Walk Test (6MWT), and WOMAC Index). These improved results persisted 12 weeks after treatment and demonstrated the better therapeutic effects of high-intensity laser therapy [40].

Ekici Ö. et al. (2022) report better treatment outcomes with high-intensity laser therapy compared to TENS therapy in temporomandibular disorders. They observed a 48% reduction in pain on the VAS and an improvement in range of motion with high-intensity laser therapy, compared to 25% with TENS therapy [53]. Another study analyzed the effect of high-intensity laser therapy in combination with exercises, TENS, heat therapy, and exercises for knee osteoarthritis compared to placebo laser and standard conventional therapy (TENS, heat therapy, and exercises). The authors reported a significant improvement in pain intensity and functional improvement in both groups, but high-intensity laser therapy had a greater positive effect on muscle strength and femoral cartilage thickness [41].

High-intensity laser therapy could also be a suitable non-pharmacological alternative for treating conditions not directly related to OA. Yilmaz M. et al. (2020) report that both the high-intensity laser program and conventional physical therapy (TENS or therapeutic ultrasound), when administered in conjunction with upcoming kinesitherapy, can be effective in reducing pain, improving range of motion in the cervical spine, and enhancing patients’ quality of life. The researchers conclude that the two treatment programs have similar therapeutic effects when applied to patients with cervical pain associated with herniated intervertebral discs and can be used as alternatives to one another. This necessitates further studies in the future to determine whether any of the rehabilitation programs used may prove to be more effective [47]. Zaralieva A. et al. (2020) report that laser therapy may be an effective method in the rehabilitation process for carpal tunnel syndrome [50]. In a recent meta-analysis, de la Barra Ortiz HA et al. (2025) found that high-intensity laser therapy, administered as monotherapy or in combination (exercises, orthotics, TENS, vitamin B supplements, etc.) can significantly reduce pain and disability and improve electrophysiological parameters (distal motor latency and sensory conduction velocity) in carpal tunnel syndrome. However, the evidence is not of a high standard, which necessitates further research and refinement of laser therapy protocols [51].

In addition, clinical trials have been found that report that HILT may provide short-term pain relief; however, this therapy does not outperform placebo-HILT or standard exercises in terms of functional improvement as measured by the WOMAC scale, stiffness, muscle strength, or proprioception [54,55,56].

Despite the growing body of evidence supporting the therapeutic effects of high-intensity laser therapy for OA [44,45], it is still not recommended by the ACR (American College of Rheumatology), OARSI (Osteoarthritis Research Society International), NICE (the UK’s National Institute for Health and Care Excellence), and others. The reason often lies in the lack of standardized protocols regarding wavelength, frequency, duration, and number of procedures; reported short-term therapeutic effects; as well as a moderate to low level of evidence for therapeutic efficacy. All this requires the studies to be of increasingly higher quality and reliability.

Key findings relevant to clinical practice:

This literature review shows that incorporating low- or high-intensity laser therapy into musculoskeletal rehabilitation programs can have a positive effect on knee osteoarthritis. The rehabilitation process should cover all stages of osteoarthritis progression. Furthermore, it should incorporate various therapeutic approaches depending on the stage and activity of the disease and its impact on pain, functional activity, and independence in performing everyday activities, which can improve the clinical outcomes of the application of laser therapy:

Clinical benefits of incorporating LLLT into musculoskeletal rehabilitation programs for knee osteoarthritis:

• When incorporated into rehabilitation programs for osteoarthritis of the knee (OA), LLLT can significantly reduce pain and improve joint function and mobility;
• The use of LLLT can improve functional activity and daily functioning, most commonly assessed using the WOMAC scale;
• LLLT shows the best and most long-lasting results (up to 6–12 months) when used as a preparatory or adjunctive procedure prior to kinesiotherapy, strength training, or stretching exercises;
• LLLT reduces inflammation and pain, allowing patients to perform exercises more actively and effectively;
• Prolonged or repeated application of the therapy helps maintain the achieved functional capacity;
• Clinical success depends on adherence to the internationally recognized recommendations provided by the World Association for Photobiomodulation Therapy (WALT). The application of the optimal wavelength (most commonly in the infrared spectrum: 808–904 nm) and the therapeutic energy dose are crucial for achieving a therapeutic effect.

Clinical benefits of incorporating HILT into musculoskeletal rehabilitation programs for knee osteoarthritis:

• HILT uses significantly higher peak power than LLLT, which allows it to reach deep-seated joints;
• When incorporated into rehabilitation programs, HILT leads to a reduction in pain intensity (VAS) in patients with knee osteoarthritis;
• HILT provides a rapid onset of analgesic effect after just the first few sessions, with continued improvement after the completion of the treatment course;
• HILT provides deeper energy penetration and achieves faster and longer-lasting pain relief compared to LLLT;
• HILT has a marked positive effect on morning stiffness and functional capacity, as measured by the WOMAC and Lequesne indices;
• HILT may improve tissue perfusion and likely affect femoral cartilage thickness in osteoarthritis of the knee (OA);
• HILT may be more effective than TENS and therapeutic ultrasound in terms of the duration of the analgesic effect and improvement in functional activity;
• The highest clinical efficacy can be achieved when HILT is administered as part of a combined program with therapeutic exercises and active physical therapy.

Limitations

This review has several limitations. Given that it is a narrative review, no systematic search or quantitative meta-analysis was conducted. The search was limited to full-text articles in English and Bulgarian; therefore, studies published in other languages and/or those to which full-text access was not available were not included. On the other hand, the possibility of bias in the selection and interpretation of the articles included in this review cannot be excluded. Identifying more high-quality scientific studies could likely minimize the risk of inaccuracy in the interpretation of the findings

5. Conclusions

The use of LLLT and/or HILT (low-level and high-intensity laser therapy) in musculoskeletal rehabilitation programs may have a positive effect on knee osteoarthritis by improving tissue trophism and reducing complaints: pain reduction, improved range of motion, and enhanced functional activities in the patients, whilst potentially contributing to a reduction in the use of pharmacological agents.

However, there is no convincing evidence of the therapeutic effects of laser therapy, and at the same time, various devices and treatment protocols are in use. For all these reasons, at this stage there are no strong recommendations for incorporating LLLT and/or HILT into osteoarthritis management programs. Therefore, it is necessary to standardize laser therapy protocols and to conduct higher-quality scientific studies in the future.