J Acupunct Meridian Stud. 2015 (Feb); 8 (1): 2–16 ~ FULL TEXT
Dina Law, Suzanne McDonough, Chris Bleakley, George David Baxter, Steve Tumilty
Centre for Health, Activity and Rehabilitation Research,
School of Physiotherapy,
University of Otago,
Dunedin, New Zealand
Laser acupuncture has been studied extensively over several decades to establish evidence-based clinical practice. This systematic review aims to evaluate the effects of laser acupuncture on pain and functional outcomes when it is used to treat musculoskeletal disorders and to update existing evidence with data from recent randomized controlled trials (RCTs). A computer-based literature search of the databases MEDLINE, AMED, EMBASE, CINAHL, SPORTSDiscus, Cochrane Library, PubMed, Current Contents Connect, Web of Science, and SCOPUS was used to identify RCTs comparing between laser acupuncture and control interventions. A meta-analysis was performed by calculating the standardized mean differences and 95% confidence intervals, to evaluate the effect of laser acupuncture on pain and functional outcomes. Included studies were assessed in terms of their methodological quality and appropriateness of laser parameters. Forty-nine RCTs met the inclusion criteria. Two-thirds (31/49) of these studies reported positive effects, were of high methodological quality, and reported the dosage adequately. Negative or inconclusive studies commonly failed to demonstrate these features. For all diagnostic subgroups, positive effects for both pain and functional outcomes were more consistently seen at long-term follow-up rather than immediately after treatment. Moderate-quality evidence supports the effectiveness of laser acupuncture in managing musculoskeletal pain when applied in an appropriate treatment dosage; however, the positive effects are seen only at long-term follow-up and not immediately after the cessation of treatment.
Keywords: acupuncture therapy; low-level laser therapy; pain; review
From the FULL TEXT Article:
Musculoskeletal disorders represent a significant cost to the
health care system.  A recent report estimated that 1.7
billion individuals globally are affected by various kinds of
musculoskeletal problems, and highlighted the considerable
impact of chronic pain and disabilities upon individuals.  Coupled with the increasing risk factors such as obesity,
sedentary lifestyles, and aging populations in the modern
world [3, 4], increasing prevalence of musculoskeletal disorders
is foreseeable, exacerbating the health care burden.
Recent research confirms that treatments such as physical
therapy, acupuncture, and massage remain popular
with pain sufferers. A survey conducted in 16 European
countries showed that 70% of participants who suffered
from musculoskeletal pain sought other forms of treatment
apart from medication.  Acupuncture is one of the most
common types of alternative treatments for patients looking
for long-term pain management , which is a relatively
safe procedure with minimal side effects. Growing demand
for, and provision of, acupuncture services have been seen
in different countries [5, 7, 8], resulting an interest in, and
rapid development of, acupuncture research in order to
establish a more solid evidence-based practice. 
Such research development extends to other forms of
acupuncture apart from the traditional needling method.
The use of low-level laser to stimulate acupuncture points
is suggested to be a safer technique due to its noninvasive
nature and its acceptability to people with needle phobia.  Laser acupuncture is considered to be an effective
alternative to traditional needling, is useful in patients who
are needle phobic, or can be used at acupuncture points
that require complicated application of the needle. [10, 11]
Ever since laser acupuncture studies were conducted in
the 1970s [12, 13], researchers have focused on the underlying
mechanism of laser acupuncture to build the scientific
basis for clinical practice. Controversy remains concerning
the mechanisms of laser acupuncture, which, being free
from any mechanical stimulation, do not share similar pain
modulation pathways to those of traditional needling
acupuncture.  Rather than producing a “needling
sensation,” the acupuncture point irradiated by the laser
needs to receive sufficient energy to elicit the physiological
effect at the cellular level, based upon the wider principle
of “photobiomodulation”. [14–16] A key point to determine
the effectiveness of laser acupuncture is the dosage
applied: this issue has been stressed in several recent papers. [16, 17] The development of dosage guidelines for
laser acupuncture is confounded by the lack of a clear
understanding of the mechanisms underpinning such
treatment, as dosage dependency is normally explored
during the stage of in vitro and animal studies.  At
present, the World Association for Laser Therapy guidelines
for low-level laser therapy published in 2010 provide
recommendations for general laser treatment for different
conditions only; no specific guidelines have been developed
for laser acupuncture. [18, 19] Hence, selection of laser
parameters and dosage is often subjective or based on
clinical experience. Studies may involve the use of an
inappropriate dosage or report the parameters inadequately;
hence, the results of these studies would be
difficult to replicate or provide data to formulate the most
efficacious dose. [20–22]
More recent evidence supports the physiological effects
of laser acupuncture, including anti-inflammatory  and
antinociceptive effects.  Such studies highlight the
potential effect of laser acupuncture under well-controlled
conditions; however, whether or not these results can be
extrapolated to the clinical setting remains unclear. It is
critically important to understand the relevance of laser
irradiation parameters, together with the appropriate selection
of acupoints, to the effectiveness of laser
acupuncture for musculoskeletal conditions.
Despite the growth of evidence in the field of laser
acupuncture, its effectiveness for musculoskeletal condition
remains unclear because of inconclusive results from
different studies. [14, 20, 22] This expansion may suggest a
shift in the evidence base; therefore, it is timely to review
the results from recent studies to confirm the current evidence
base for laser acupuncture. A systematic review with
meta-analysis was, therefore, conducted to update the
previous review in this area , with the following aims:
(a) to assess the clinical effectiveness of laser acupuncture for relieving pain and improving functional outcomes when used for treating musculoskeletal conditions;
(b) to explore the relationship between parameter choice and outcomes; and
(c) to establish the level of evidence of the effectiveness of laser acupuncture with an update of the current literature.
Protocol and registration
This systematic review was conducted and reported based
on the Preferred Reporting Items for Systematic Reviews
and Meta-Analyses guideline ; a pre-registered protocol
was not used.
Studies included for this review had to meet the following criteria.
Types of studies
Randomized controlled trials (RCTs) and controlled clinical
trials published in peer-reviewed journals were included. In
addition, studies published in databases since their inception
to March 1, 2013 were included, in order not to miss
any records and to update the findings of our previous
systematic review  by the inclusion of more current
publications. Due to resource limitations, this review
excluded non-English-language publications.
Types of participants
Human participants with musculoskeletal diseases or injuries,
and presenting with pain were included. Those with
systemic illness and headache were not included. There
were no restrictions based on age, gender, or physical activity
Types of intervention
Studies evaluating laser acupuncture as the primary intervention
were included. Such intervention needed to include
application of active low-level laser therapy to traditional
Chinese medicine acupuncture points, trigger points, or
tender points. Studies involving a primary intervention
using needling or other forms of stimulation on acupuncture
points, or those involving application of laser therapy to
nonacupuncture points were not considered. In addition,
those studies were included that compared laser acupuncture
with one of the following as a control intervention:
placebo or sham laser, no treatment, or other treatments,
such as medication, exercise therapy, or other electrotherapy
Types of outcome measures
These studies included those that assessed pain or function
using at least one of the following as primary outcomes: pain
level (visual analog scale), global assessment of participants’
improvement (subjective improvement, proportion
of objective measures improvement, overall improvement),
or a functional outcome measure (validated questionnaire or
functional scale specific to the presenting condition).
Length of follow-up
No restriction was applied to the length of follow-up.
Studies were identified by an electronic search of the
following databases: MEDLINE (from 1946 to March 1, 2013),
AMED (from 1985 to March 1, 2013), EMBASE (from 1947 to
March 1, 2013), CINAHL (from 1981 to March 1, 2013),
SPORTSDiscus (from 1960 to March 1, 2013), Cochrane Library,
PubMed (from 1950 to March 1, 2013), Current Contents
Connect (from 1998 to March 1, 2013), Web of Science
(from 1900 to March 1, 2013), and SCOPUS (from 1960 to
March 1, 2013). The same search strategy was used in
subject-based databases, as shown in Appendix 1. In addition,
Google Scholar (from January 1, 2013 to March 1,
2013), Physiotherapy Evidence Database (PEDro; from 1966
to March 1, 2013), and two key journals (Lasers in Surgery
and Medicine, from 2005 to March 1, 2013; and Photomedicine
and Laser Surgery, from 2005 to March 1, 2013)
were searched manually to cover recent studies, which may
have not been included in other databases. Two independent
reviewers ran the search independently on March 1,
Selection of studies
Two independent reviewers assessed the eligibility of all
studies independently by screening the titles and abstracts
with the above selection criteria. Full-text articles were
retrieved if there was any uncertainty. When there was a
disagreement between the two reviewers, the study was
reassessed using the selection criteria as a basis for consideration
of its eligibility until consensus was achieved. Relevant
studies were retrieved as full-text articles, either from
the databases or from the study authors, for final assessment
of inclusion or exclusion. Reference lists of retrieved articles
were checked for any missing relevant articles.
Assessment of methodological quality
All included studies were assessed for methodological
quality using the PEDro scale.  Two reviewers performed
the assessment independently in a standardized
manner; they were not blinded to the details of the studies.
Disagreements between reviewers were resolved by
consensus, and a third reviewer was consulted if disagreements
persisted. Methodological qualities of the included
studies were rated from 1 to 10 on a 10–item PEDro scale.
All included studies were also assessed for their level of risk
of bias by two independent reviewers. The risk of bias
assessment helps identify any major methodological flaws
from different domains of the included studies.  Further
subgroup analyses related to bias assessment were planned
Two independent reviewers extracted data from included
studies. Disagreements were resolved by discussion; if no
agreement could be reached, a third reviewer was available
Data were extracted from each included trial on: study
population; details of interventions; types of outcome
measures; and laser acupuncture dosage (including parameters
recommended by the World Association for Laser
Therapy  or calculation of missing data if possible).
Data from included studies were pooled for further metaanalysis
where appropriate. If available, means and standard
deviations for outcome measures were extracted or
calculated using published relevant data with Review
Manager (RevMan) software, version 5.2. Copenhagen: The
Nordic Cochrane Centre, The Cochrane Collaboration, 2012.  Unpublished data were not sought from authors
because of time limitations. Data were categorized and
analyzed based on the following parameters,
(1) Pain score using a visual analogue scale and expressing the raw score on a 0–10 scale. Change in scores (difference between various time points in a study) were also considered but grouped separately.
(2) Pressure pain thresholddalgometric measurement expressed in kg/cm2.
(3) Functional scoredusing validated functional scales, measuring grip strength, or comparing the difference in functional scores prior to and after the intervention.
Dichotomous outcomes were expressed as relative risks,
and continuous outcomes were expressed as the standardized
mean difference (SMD); both were presented with 95%
confident intervals.  A negative SMD was defined to
indicate favorable effects of laser acupuncture to the
control intervention and vice versa. Magnitudes of the
overall effect size were classified as small (0.2–0.5),
moderate (0.5–0.8), and large (>0.8) according the value
of SMD using the Cohen’s categories.  Qualitative
analysis was performed if studies failed to provide data to
be pooled for analysis. Studies were assessed for heterogeneity
using the Chi-square test to decide whether a
random or fixed effect model was used; Chi-square test
with a p ≥ 0.05 indicates a significant heterogeneity.  I2
value quantifies the degree of heterogeneity: moderate
(I2 > 30%), substantial (I2 > 50%), and considerable
(I2 > 75%). 
Subgroup and sensitivity analyses
Subgroup analyses were conducted to evaluate the
following overall effects: (1) diagnosis; (2) control intervention;
(3) follow-up perioddmeasures taken immediately
at the end of the intervention (short-term effect) or
from 6 weeks to 26 weeks postrandomization (long-term
effect); and (4) site of laser acupuncture, application acupuncture
point, trigger point, or tender point.
Sensitivity analyses were conducted for testing the
robustness of the pooled effect size. Effects were examined
according to risk of bias, to ensure that the analysis
was not biased by any study with a large number of methodological
Risk of bias across studies
The risk of publication bias was assessed by analyzing the
symmetry of the funnel plots generated by RevMan (The
Cochrane Collaboration). Symmetrical funnel plots represented
lower risk of bias, whereas higher risk of bias was
demonstrated by increased asymmetry. 
Quality of evidence
The Grading of Recommendations Assessment, Development,
and Evaluation approach was used to judge and
categorize the quality of evidence for the primary outcomes.  This reflects the extent of confidence of the
estimated effects by considering the study design and other
confounding factors that may affect the judgment.
following quality grades used were used.
(1) High quality:
“We are very confident that the true effect lies close to
that of the estimate of the effect”.
(2) Moderate quality:
“We are moderately confident in the effect estimate: the
true effect is likely to be close to the estimate of the effect,
but there is a possibility that it is substantially
(3) Low quality: “Our confidence in the effect
estimate is limited: the true effect may be substantially
different from the estimate of the effect”.
(4) Very low
quality: “We have very little confidence in the effect estimate:
the true effect is likely to be substantially different
from the estimate of the effect”.
Figure 1 depicts the process of study selection with the
Preferred Reporting Items for Systematic Reviews and
Meta-Analyses flow diagram. The search was conducted on
March 1, 2013, and a total of 2,093 potential relevant records
were retrieved. After adjusting for duplicates, 1,432
records remained. One additional study was retrieved from
Google Scholar. A total of 49 studies met the inclusion
criteria and were included in the current review.
Table 1 [33–81] summarizes the characteristics of all 49
included studies. All studies were RCTs published in English.
A total of 2,360 participants, aged ≥ 18 years, were
involved. All trials were conducted in either a primary or a
secondary health care setting. Participants received from
three to 15 treatment sessions over a period of 1–12 weeks.
Laser acupuncture was performed by physiotherapists or
other trained health care professionals in most of the trials;
however, half of the studies failed to report this clearly.
Quality assessment of included studies
Appendix 3 shows the methodological assessment of the
included studies using the PEDro scale.  Thirty studies
(61%) were considered to be of high methodological quality
with a moderate cut-off score of 6.  The most common
flaws were inadequate allocation concealment (78%), lack
of blinded therapists (63%), and lack of intention-to-treat
analysis (71%). Despite the possible bias related to these
flaws, other criteria were adequately addressed to minimize
the risk of bias. Almost all the studies (94%) performed
adequate randomization, thereby reducing possible selection
bias. In most of the studies, patients (81%) and assessors
(63%) were blinded successfully. Almost three-quarters
(73%) of the studies provided adequate follow-up data with
< 15% dropout rate; therefore, attrition bias was lowered.
Inter-rater agreement was at an acceptable level, and
disagreements were resolved by consensus.
Evaluation of the included studies using the risk of
bias assessment tool provided by the Cochrane collaboration  showed similar results to that using the PEDro
score (see Figure 2). Risks of selection bias and performance
bias were mixed, as risks of some of the studies were unclear
due to insufficient description. Other domains
remained at low risk in all the included studies, except
for 20% of the studies that exhibited high risk in attrition
due to high dropout rates or nondescription of reasons for
Effects of laser acupuncture
Thirty-three studies provided sufficient data to calculate
effect sizes for key outcome measures using RevMan (The
Cochrane Collaboration) and were included in the metaanalysis.
These studies showed mixed results, as reported
by the authors, with two-thirds reporting positive effects
favoring laser acupuncture, and one-third inconclusive or
All 33 studies assessed pain as one of the primary outcome
measures. However, due to the heterogeneous characteristics
of studies, results for pain scores were subcategorized
into laser acupuncture versus placebo or laser acupuncture
versus other interventions. To account for possible variation
among different studies, the random effects model was
used and the pooled effects were expressed as the SMD.
When compared with the placebo intervention, the overall
effect for pain favored laser acupuncture, both at the end
of intervention (SMD –0.43; –0.74 to –0.12) and at the
follow-up period (SMD–0.61;–1.12 to–0.10). The pooled
effect sizes of laser acupuncture for pain were considered
to be small at short-term follow-up, but showed a moderate
effect at long-term follow-up (see Appendix 4). Other
[40, 41, 44, 47, 48, 50, 54, 57, 61, 62, 74, 80] expressed
the pain change scores from baseline, and showed a similar
effect on pain relief at both short-term(SMD–0.53;–0.95
to –0.10) and long-term follow-ups (SMD –0.77; –1.25
to –0.29). When compared with other interventions,
results of pain scores were mixed. Laser acupuncture
failed to show significant favorable effects on pain scores
at any time point compared to the control treatment
(SMD –0.23; –1.00–0.54; SMD –1.43; –3.84–0.98).
Nine studies investigated pain by measuring the pressure
pain threshold. [36, 38, 39, 43, 51, 58, 59, 64, 69] A positive effect
indicates the beneficial effects of laser acupuncture as
compared to control interventions. Similarly, compared
with a placebo group, results showed a strong positive effect
in favor of the experimental group at the end of
intervention (SMD 1.02; 0.72–1.33) and during the follow-up
period (SMD 0.91; 0.30–1.53). Comparing laser acupuncture
to other interventions, no short- (SMD 0.35; –0.01–0.71) or
long-term effects (SMD 0.20; –0.26–0.66) were found on
the pressure pain threshold (see Appendix 4).
In the studies measuring pain with a visual analogue
scale, subgroup analysis of pain scores was performed for
the three most common diagnoses: myofascial pain or
musculoskeletal trigger point syndrome, lateral epicondylitis,
and temporomandibular joint pain (Figure 3). The
subgroup differences were not significant at the end of
intervention and during the follow-up period (p > 0.05). The
overall effect on pain in the short term moderately favored
laser acupuncture (SMD –0.49; –0.79 to –0.18). Effects
calculated from long-term follow-up almost doubled, which
suggested that laser acupuncture has a strong beneficial
effect on pain (SMD –0.95; –1.55 to –0.35).
Myofascial pain/musculoskeletal trigger points
Among 13 studies investigating the effectiveness of laser
acupuncture for myofascial pain or musculoskeletal trigger
points, only six showed favorable effects at the end of
intervention. [61, 63, 64, 66, 67, 77] During the follow-up
period, four out of six studies demonstrated a positive effect
in favor of laser acupuncture. [39, 59, 63, 77] In most of
the studies showing no significant effect of laser acupuncture,
laser parameters were reported inadequately. [34, 45, 50, 52, 58, 69] The overall effect of laser acupuncture
on pain was positive, with a moderate effect at short
term (SMD –0.49; –0.83 to –0.16) and a strong effect at
long term (SMD –0.95; –1.68 to –0.23).
Two studies examined the effect of laser acupuncture on
lateral epicondylitis and showed conflicting results. [40, 51]
The overall effects did not suggest any favorable result of
laser acupuncture at any time point. The study by Emanet
et al  reported a positive conclusion during the followup
period; yet the effect was not significant (SMD –0.42;
–1.00–0.16). Again, the laser parameters employed in this
study were unclear and incomplete; thus, it is not possible
to estimate whether or not the dosage was appropriate.
Temporomandibular joint pain
Two studies [33, 36] compared laser acupuncture with placebo
in treating temporomandibular joint pain at the end of
intervention. Mixed results were obtained: one was positive  and the other one was inconclusive.  The latter
study involved two laser acupuncture groups receiving
different dosages. The group that received a higher dosage
showed a better effect of laser acupuncture compared with
the group receiving a lower dosage; however, neither of
them have a significant effect on pain. During the follow-up
period, only one study  provided data; hence, outcome
effect was not estimated.
Most of the studies assessed functional improvement using
a wide range of scales. Each study could involve multiple
results from different functional scales; hence, an estimated
overall effect size across the studies was not
possible. Studies were more likely to report positive effects
during the follow-up period rather than at the end of the
intervention. Only two out of 11 studies [51, 63] reported a
positive short-term effect on functional outcomes, while
six out of eight studies [39, 40, 51, 57, 62, 63] showed positive
effects at long term (see Appendix 4).
Two studies [40, 51] investigated lateral epicondylitis;
the pooled effect sizes of handgrip strength strongly
favored laser acupuncture at both time points, but were
significant only during the long-term follow-up period
(MD5.16; 1.14–9.19). In regard to the small number of
studies analyzed, it is important not to overlook this significant
pooled effect (see Appendix 4).
Sensitivity analyses were conducted to explore whether
or not the above mentioned main findings were affected by
any studies with high risk of bias in certain domains. We
exclude studies with any of the following: high risk of
attrition bias, selection bias, and performance bias. No
significant difference was found after excluding high-risk
Appropriateness of laser acupuncture treatment
All included studies were analyzed for the appropriateness of
laser parameters used. They were grouped separately into
those reporting positive effects and those reporting inconclusive
or no effects, and are displayed, along with the parameters
used, in Tables 2 and 3 [33–81], respectively. It is
notable that four studies [52, 59, 74, 80] reportedno significant
difference between groups; by contrast, their calculated
effect sizes from RevMan (The Cochrane Collaboration)
analysis favored laser acupuncture.
Almost 70% of studies reporting positive results used the
clinically appropriate dosage suggested by Baxter et al. 
Their systematic review stated that laser acupuncture
would be effective when irradiation is applied at a minimum
average output power of 10 mW and an energy dose of
at least 0.5 J per point.
By contrast, studies reporting inconclusive or no effect
of laser acupuncture either failed to describe the parameters
comprehensively or applied an inappropriate dosage.
Half of these negative studies are deemed of low
methodological quality, with PEDro scores of < 6.
The most common sites for the application of laser
acupuncture were trigger points (39%). Subgrouping to
perform another analysis to examine any difference of the
effects on pain with different application sites was performed.
No significant difference was observed between
the subgroups at the end of intervention and during the
follow-up period (p > 0.05). However, only the application
at trigger points showed a positive effect in favor of laser
acupuncture; this was not seen in case of application at
acupuncture points or tender points. (see Appendix 5).
Risk of bias across studies
Considering the heterogeneity of the studies, funnel plots
were drawn according to different outcome measures. Visual
assessment of funnel plots did not show any considerable
asymmetry, indicating a comprehensive coverage of
publications. Hence, publication-related bias was low in
This systematic review investigated the clinical effectiveness
of laser acupuncture, focusing on its effects on pain
and functional outcomes while treating musculoskeletal
disorders. The current findings strengthen the evidence
from a previous systematic review.  The key findings in
the current review support the continued use of laser
acupuncture for treating musculoskeletal pain. Results
from the meta-analysis suggest that the effect of laser
acupuncture on pain and functional outcomes tended to be
more significant during long-term follow-up periods rather
than at the end of intervention. These results indicate that
laser acupuncture may be effective in treating musculoskeletal
pain and improving function if an adequate dosage
is used, and that the effects are long lasting, as evidenced
by the increase in effect sizes demonstrated in the metaanalysis
at 6–26 weeks postrandomization. It is important
to stress that results from the included studies were
dependent upon the appropriateness of laser parameters
used. Studies with higher methodological quality, which
also reported dosages properly, showed a more consistent
result, with a favorable effect of laser acupuncture on both
pain and functional outcomes.
To the best of our knowledge, there has been no further
evaluation of the latest literature on laser acupuncture
since a previous systematic review.  It concluded that
laser acupuncture was an effective treatment for myofascial
pain, based on a moderate level of evidence from 18
RCTs that were published prior to 2005. A massive growth in
publications in recent years has provided further evidence
on the effectiveness of laser acupuncture. Not surprisingly,
a large number of clinical trials were identified from the
current literature, most of which were published during the
past decade. The total number of eligible studies included
in this systematic review was more than twofold that of the
past review. 
The majority of studies reported positive findings on the
effects of laser acupuncture on both pain and functional
outcomes; by contrast, one-third of reviewed studies reported
no benefit. Given the heterogeneity of included
studies, meta-analyses were performed using subgroups of
studies according to their study populations and follow-up
time point. The three most common diagnoses were
analyzed separately in order to have a minimum of two
studies for each analysis. Sensitivity analyses excluded
studies comparing laser acupuncture with other active
treatments, as the primary scope of this review was to
evaluate whether or not laser acupuncture is effective,
rather than comparing its effectiveness with other active
Myofascial pain/musculoskeletal trigger points
Ten studies showed positive effects of laser acupuncture on
myofascial pain or pain at trigger points: four studies [34, 50, 52, 58] had an individual effect size that did not
favor the laser group. Coincidently, all these studies did not
include follow-up assessments to investigate possible longterm
effects. Given the increased effect sizes at follow-up,
as highlighted here, it is possible that these researchers
might have overlooked a potential effect in the longer
term; another study  found positive effects only during
the follow-up period, but not at the end of intervention.
Emanet et al  showed more favorable effects in the
short term than in the long term. However, the individual
effect size (for pain) from the forest plot crossed zero at
the long-term time point, indicating a lack of statistical
significance. Although the pooled effects from another
study  did not suggest any favorable outcome for
treatment with laser acupuncture to reduce pain in lateral
epicondylitis, results for handgrip assessment yielded some
interesting findings. Both studies investigated the effectiveness
of laser acupuncture by evaluating pain and
functional outcomes, and appeared to be more homogeneous,
so the mean difference was used as the pooled effect
result. Again, the estimated effect size for functional
outcome (handgrip) favored laser acupuncture, especially
during the follow-up period. However, it should be stressed
that this analysis is based on two studies examining laser
acupuncture, and the result may not be generalized to
Temporomandibular joint pain
The three studies reviewed showed mixed results, and only
one of these reported outcomes at long term. At short
term, the effect was inconclusive. No further analysis was
carried out to compare the effects at different time points.
Increased long-term follow-up effects
Findings related to the three different diagnoses showed a
consistent trend of better pain-relieving effects during the
follow-up period. Pooled effect sizes were doubled during
the follow-up period compared to those at the end of
intervention. This phenomenon may account for the conflicting
results from some of the negative studies. Without
taking into consideration the possibility of delayed or longlasting
effects, their conclusions of lack of effectiveness
may be flawed. Results from our analyses included both
short- and long-term follow-up data; these data were
separated into similar time points to allow more comparable
Weaknesses of negative studies
The five studies [38, 42, 46, 50, 74] that found no significant
benefit of laser acupuncture had a number of shortcomings.
In one study , a mismatch was found between the
calculated individual effect and the authors’ conclusion.
Although the effect size (expressed in the SMD) for pain
favored laser acupuncture, Vecchio et al  reported no
benefit. This apparent error was also highlighted by another
systematic review , which suggested a flaw in their
analysis. In another study on back pain, Glazov and colleagues  performed a post hoc analysis on their data,
which challenged the results of their original study. 
They suggested that the randomization failed to create
comparable groups and resulted in an imbalanced baseline
characteristic that responded differently to the intervention.
The PEDro quality rating of the study by Katsoulis et al  was exceptionally low (2 out of a PEDro score of 10),
representing a major performance bias. The remaining two
studies [38, 50] applied laser acupuncture around the neck
and upper trapezius muscles area. The parameters selected
in both studies were similar to the other two positive
studies [57, 66] targeting the neck region, but the authors’
conclusions were based on results measured only at short
term. Consequences of these apparent methodological
flaws may be an underestimation of the true effect of laser
acupuncture from these studies.
Clinical relevance of the laser parameter
Variation in application of the laser acupuncture intervention
can very likely account for a certain degree of difference
in outcomes. Such clinical heterogeneity should
be considered when evaluating the effectiveness of a
therapy. Laser acupuncture has been suggested to be a
dosage-dependent modality [16, 21]; these sources suggest
that the energy delivered to the target point by laser
acupuncture has to reach a threshold in order to produce a
desired effect. Thus, the dosages reported in the included
studies may explain the observed difference in outcomes.
Characteristics of the laser beam and the application site of
the laser would directly affect the actual energy received
by the target point. [10, 14] Although detailed discussion of
the potential mechanisms of laser acupuncture is beyond
the scope of this review, the importance of selecting
and reporting parameters accurately is paramount to understand
and interpret the results of individual studies.
Unfortunately, the quality of reporting of parameters
and dosages varied among the studies included in this review;
five studies stated neither the power density nor the
irradiated area. [40, 58, 59, 64, 75]. This brings into question
whether or not an appropriate dosage was applied.
Reporting of these parameters is essential, as recommended
by the World Association for Laser Therapy guidelines , to determine the appropriateness of the dosage.
In addition, unclear reporting of parameters was more
commonly seen among studies with negative or inconclusive
results (Tables 2 and 3).
It is challenging to draw meaningful conclusions
regarding an effective dosage window from these studies
due to the variation in the application of laser acupuncture
and the wide dosage range employed. This systematic review
covered different musculoskeletal conditions, and
each condition may have required a distinct parameter and
dosage regime for clinical effectiveness. Site of application
is a key factor in the selection of parameters, given that
there may be a specific acupuncture point for a particular
diagnosis. In this review, the point of application was not
limited to acupuncture points only, but included trigger and
tender point applications as well, because a wide range of
evidence suggests overlapping of acupuncture points. [84-83]
It seems unwise to exclude those studies using
trigger points or tender points even though the existence of
these specific points is still controversial. [85, 87, 88]. A
subgroup analysis based on different application sites was
performed; however, no obvious difference could be seen
between groups. Application on acupuncture, trigger, and
tender points appeared equally effective.
Quality of included studies in our review
The number and proportion of trials rated to be of high
methodological quality doubled in this review, compared to
a previous review.  Over two-thirds of the 49 RCTs
included in this review were high-quality studies, whereas in
the previous review less than one-third of the studies
were of high quality. Considering this growth in the number
of higher-quality studies in this body of literature, the
findings of this systematic review were expected to be more
There was an apparent relationship between levels of
methodological quality and reported results. Two-thirds of
high-quality (PEDro score ≥ 6) studies reported beneficial
effects of laser acupuncture, which is similar to the proportion
for all included studies. Lower-quality studies
appeared to show more conflicting results, with equal
numbers of studies reporting benefits (n = 9) or no benefits
(n = 9). This methodological heterogeneity should be
considered when assessing the overall pooled effect in the
meta-analysis. However, it should be stressed that the
sensitivity analyses, excluding studies with high risk of bias
in various domains, failed to show any differences in overall
findings that conflicted with the effects estimated.
The limitations of this review include potential bias related
to heterogeneity and methodological quality of the
included studies. These problems were anticipated while
designing the methodology of this review, and so different
subgroup analyses were initiated to address this limitation.
Another limitation of this review is that some of the studies
have a high risk of bias in some of the domains; however,
the sensitivity analyses suggested no major effects upon
the outcomes. Lastly, even though non-English publications
were excluded, the funnel plot assessment did not detect
any potential publication bias. Although this kind of visual
assessment is considered to be prone to error , it is one
of the most common methods adopted for detecting publication
bias owing to its simplicity.  Given the large
number of studies included in this meta-analysis, funnel
plot should be able to detect possible bias.
Using the Grading of Recommendations Assessment,
Development, and Evaluation system , the strength of
recommendation is based on not only the quality of the
evidence, but also other factors that should not outweigh
the benefit of the treatment. Using pain and functional
outcomes to assess the clinical effectiveness of laser
acupuncture, most of the included studies were found to be
high-quality RCTs, providing high-quality evidence. Yet the
quality of evidence was downgraded (–2) due to inconsistency
and imprecision of the results for both pain and
functional outcome measures.  Owing to the possible
dose response for pain-relieving effects, and a large effect
from functional outcome, the quality of evidence was
upgraded (+1). As a result, there is a moderate quality of
evidence supporting the effectiveness of laser acupuncture
for treating pain and improving functional outcomes in
musculoskeletal disorders. It suggests with moderate confidence
that the estimated effect from the meta-analysis is
likely to be close to the true effect. Serious adverse events
have seldom been reported for laser acupuncture, given its
noninvasive nature; this is in keeping with the results of all
the included studies. Based upon this systematic review, a
strong recommendation can be made that laser acupuncture
is effective for improving musculoskeletal pain and
functional outcomes at 6–26 weeks.
Overall, the evidence is sufficiently robust to determine the
effectiveness of laser acupuncture at long term for treating
musculoskeletal conditions. In trials reporting negative or
inconclusive results, neither enough evaluation was carried
out nor were the participants followed up to a sufficient
time point. These trials did not allow complete evaluation
of pain and functional outcomes, and their conclusions
were made based upon results measured at short term only.
Hence, this review highlights the importance of providing a
sufficient course of treatment to allow laser acupuncture to
work effectively in the clinical situation.
Although the evidence does not allow us to determine an
effective dosage window for laser acupuncture, the
possible range of applications was largely adjusted and
designed to fit specific musculoskeletal conditions. To foster
the development of clinical guidelines, future research
should carefully define the study population and provide
rationale for the parameters chosen. This would facilitate
not only pooling of data for meta-analysis, but also more
precise analysis for a specific condition or application site.
With the improvement in quality of evidence over time,
more robust recommendations for clinical application of
laser acupuncture can be anticipated in the future.
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The authors declare that they have no conflicts of interest
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