Journal of Rehabilitation Medicine 51-11 | Page 12

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L. Chen et al.
PEMF therapy showed no advantage in the reduction
of WOMAC pain score, VAS pain score or WOMAC
stiffness score.
Joint pain and stiffness are the most common and
prominent symptoms of knee OA, and the guidelines
developed by the OA Research Society International
recommend that improving pain and stiffness should
be the primary goal of treatment (25). However,
previous systematic reviews have shown significant
controversy over whether PEMF therapy has any effect
on improving pain and stiffness in knee OA. Only one
review clearly supports its ability to relieve pain (11).
Furthermore, studies often neglected to analyse the ef-
fect of PEMF therapy on join stiffness. In addition, we
found that previous studies included some low-quality
non-randomized controlled trials and the pooled results
included other physical therapies, such as pulsed short-
wave (9, 11, 12). Unlike previous systematic reviews,
only randomized placebo-controlled trials concerning
classic PEMF therapy, as well as 3 newly published
RCTs with high-quality methodology (15–17), were
included in this analysis, and the results confirmed
that PEMF therapy had no advantage in improving
patients’ joint pain or joint stiffness over a period of
approximately 1 month. A possible explanation for
this is that subchondral bone, periosteum, synovium,
ligament, and joint capsule are rich in innervation, thus
the nerve endings are the origin of pain caused by OA
nociceptive stimulation (26, 37). However, studies
have shown that PEMF therapy has an effect on arti-
cular cartilage regeneration and repair, but since there
are no nerves or blood vessels in cartilage, cartilage
injury does not directly cause pain and, consequently,
there is no significant improvement in pain with PEMF
therapy (28–30).
In the meta-analysis of VAS pain score, significant
heterogeneity was found among the included studies.
This significant heterogeneity remained after sensiti-
vity analysis was conducted by eliminating each study
individually, although this heterogeneity was notably
reduced if the study published by Ay & Evcik (18)
was eliminated. Nevertheless, there was insufficient
evidence to suggest that this study had methodological
deficiencies or was of poor quality, thus it was not ex-
cluded, although this may have resulted in an influence
on the pooled result of VAS pain score. A possible
explanation for this is that there may be differences
in the frequency, intensity, or treatment regimen of
PEMF therapy among these included trials. At present,
due to the limited clinical research data on the appli-
cation of this treatment to OA, there is no consensus
on standardized parameters of PEMF therapy, such as
frequency, intensity, pulse length, or pulse waveform
www.medicaljournals.se/jrm
for the safest and most effective treatment, and more
clinical research data is needed (31, 32).
Previously, there have been 3 systematic reviews that
analysed whether PEMF therapy can improve physical
function for patients with knee OA. Among them,
one review (12) concluded that PEMF therapy had no
significant effect on physical function, while the other
2 (9, 10) showed that PEMF therapy was beneficial in
improving physical function. A possible explanation
for this discrepancy is that 2 clinical studies involved
classical PEMF therapy, while another 2 clinical stu-
dies used typical pulsed short-wave. These were all
included without subgroup analysis in the previous
systematic review, which drew the opposite conclu-
sion (12). In this meta-analysis of physical function,
the observed WMD was –5.28, and reached above
minimal clinically important differences, suggesting
that PEMF therapy may improve physical function
(33). Possible factors for this are that PEMF therapy
can elicit strong effects on the vitality and prolifera-
tion of human chondrocytes and on the synthesis of
chondrocyte extracellular matrix in vitro (34–36).
Despite bone and cartilage metabolism promoted by
short-term PEMF therapy, the treatment may not lead
directly to improvement in local joint symptoms; it
may reduce the clinical global impression of severity
and improve patients’ global impression, which may be
related to the improvement in activities of daily living
measured by the WOMAC physical function subscale.
There are still some limitations to the current study.
Firstly, only 8 RCTs were included, resulting in a
relatively small sample effect. Secondly, only studies
published in English were included. Finally, there was
significant heterogeneity in the meta-analysis of VAS
pain score, possibly due to variations in the frequency,
intensity, treatment regimen, and duration of PEMF
therapy among the included trials. In addition, since the
VAS is a self-report measure assessing pain intensity,
it may result in relatively strict or loose ratings among
included studies. Although the PRISMA guidelines
and Cochrane Handbook for Systematic Reviews of
Interventions were used to assess the included studies
to ensure reliable and verifiable results, more RCTs
are needed to provide further validation.
In conclusion, this meta-analysis showed that, de-
spite having no advantage in the management of pain
and stiffness, PEMF therapy is beneficial for improving
clinical symptoms such as physical function in patients
with knee OA. This means that PEMF therapy may
be a useful and economic adjuvant treatment for non-
surgical management of knee OA. Further research is
needed to determine the optimal frequency, intensity,
treatment regimen and duration of PEMF therapy.