The use of Pulsed Electromagnetic Field (PEMF) Therapy has become increasingly popular because it is simple, non-invasive, safe… and, of course, appears effective in many therapeutic purposes. It is promoted for having anti-inflammatory effects, and possibly inducing a diverse range of changes within tissues (eg: improved cell differentiation and migration, cell reprogramming, brain glucose metabolism and therefore local brain activity). Here we look a bit deeper at the evidence behind marketing folks’ promises This week we’ll focus on its potential in musculoskeletal conditions such as arthritis and back pain. Stay tuned next week for its effect on the brain and other dimensions of health.
- Magnetic coils induce pulsed electric fields in the body, which are thought to elicit responses within cells by acting on cell membrane receptors, ion channels and/or synapses between neural cells.
- There are select musculoskeletal uses of PEMF: it seems to promote bone growth/healing, provide some benefits to arthritis of the knee (and possibly other joints), low back pain and other analgesic needs.
- In most of these applications, there are limits to our knowledge of the mechanisms by which PEMF works. We also do not understand what the ideal protocols for stimulation may be. If the research can rectify these, PEMF may become an easy, viable and valuable means to optimise health in the future.
How PEMF works
Magnetic coils are placed on the body to induce pulsed electric fields in the body’s conductive tissue. PEMF energies/frequencies are typically extremely low- between 5-300 Hz (or cycles/second). Occasionally, higher short wave frequencies (eg: 27 MHz) feature.
Common views are that the magnetic stimuli influence receptors or ion channels on the membrane of cells, which then elicits responses within the cell. Or it can influence activity at synapses (the points of connection between neurons). However, the interactions between tissues and PEMF’s low‐energy signals are still incompletely understood.
PEMF for osteoarthritis
PEMF is popular as a treatment for osteoarthritis- despite a lack of definitive evidence for it.
For example, it’s often used for knee arthritis- one of the most common types of joint problems around, aggravated by common factors such as age, wear and tear, and obesity. Recent systematic reviews and meta-analyses have found that PEMF can increase the knee’s physical function and capacity for activities of daily living, but doesn’t seem to reduce stiffness or pain. Other studies have made conflicting suggestions regarding the impact on pain and stiffness.
It seems- from cell and animal models only- that PEMF may enhance cartilage regeneration and repair. It has increased the synthesis of growth factor, leading to enhanced proliferation of cartilage cells.
Image credit: Background photo created by freepik – www.freepik.com
However, as there are no nerves in cartilage, this repair would have no effect on the experience of pain. On the other hand, areas around the cartilage (eg: bone, ligament, joint capsule) do have nerve supplies. So IF these areas are also subject do damage, and positively impacted by PEMF, there may be alangesic effects.
Even less evidence is available for other body parts subjected to osteoarthritis. A couple of studies have suggested that hand arthritis may be improved (in terms of function and possibly pain), but the neck doesn’t respond so well. The strength of these trials is insufficient however, so we need to err on the side of caution with such conclusions.
Meta-analysis suggests PEMF sessions of 30 minutes or less may be more effective against osteoarthritis than sessions lasting up to 60 minutes. It seems that 5-20 minutes produces the greatest increase in markers of cartilage cell development. Another two studies have shown that PEMF could activate healing signal pathways within cells within 5–10min, and the signaling might be largely dulled after 30min.
A 2018 review of literature identified three trials reporting side effects from PEMF. These included increased knee pain, hip pain, spine pain, vomiting, a warming sensation, increased blood pressure, numbness of feet, and even disease to the heart muscle.
As in many areas, it’s difficult to identify the specific parameters of PEMF (frequency, pulse intensity etc) which are most useful.
PEMF and bone health
A variety of evidence, including from animal and human cell cultures, plus clinical trials, indicate that PEMF can assist bone healing. Thus it has potential in the treatment of issues such as osteoporosis and cases where ends of bones don’t fuse (eg: following fracture). It is thought that the electrical signaling cascades elicited by PEMF ultimately promote bone formation.
However, large differences between existing studies and limited randomised controlled trials are slowing us down in understanding the precise mechanisms of this effect.
Proposed mechanisms include an increased production of growth factors, which leads to bone formation, increased collagen expression and opening of ion channels in cell membranes, which allows increased calcium levels within cells.
Formation of new blood vessels may also play a role (as it enhances the delivery of materials to the bone).
There may also be effective protocols that haven’t even been studied due to limitations in equipment availability. This also stops standards for clinical PEMF use to be developed, as we can’t determine what the optimal settings (in regards to frequencies, intensities, duration of exposure, pulse & waveforms of stimulation) are.
Just as an indication of the confusion regarding PEMF settings- it has been seen that square waves helped osteoblasts (i.e. cells that produce new bone) proliferate. Meanwhile sinusoidal waves were seen to have the opposite effect on osteoblast proliferation, but other benefits to bone.
While there’s a lot we don’t know about how to best apply PEMF, it seems that repeated sessions may be required. Single sessions may produce effects on the molecular effect but don’t seem to produce effects of clinical relevance.
Analgesic effects of PEMF
PEMF is thought to act on the Central Nervous System to reduce the sensation of both acute and chronic pain. It is possible that it could help alleviate the effects of DOMS, however there is but minimal research on this.
It is also possible that PEMF may dull the more subjective elements of pain (eg: someone’s perception of something being unpleasant) as opposed to the basic perception of painful stimuli. It may do this by increasing levels of the feel-good neurotransmitter, dopamine. There have also been studies showing reduced activity in parts of the brain associated with this subjective pain perception (the insula, anterior cingulate, and hippocampus/caudate) with PEMF applied over the skull.
The required dose for optimal effect is not clear. It may also vary according to what is the cause of pain. For example:
- Some studies have suggested that a single 30-minute PEMF session can offer relief to rheumatoid arthritis and fibromyalgia pain
- On the other hand, a small study has suggested that a single 30 minute use of transcranial PEMF is not enough to reduce pain in people with severe neuropathic pain. In these cases, damage within the nervous system causes neurons to fire inappropriately, resulting in perceived pain with both painful and normally non-painful stimuli. It can stem from various problems, such as injuries, diabetes, multiple sclerosis, and tumours
- Also, chronic localized musculoskeletal or inflammatory pain has remained steady after a trial of 7 days of treatment
PEMF for low back pain
We’re looking at this separately because of its commonality: 60-70% of people in industrialised countries will experience low back pain over their lifetime.
Studies suggest that PEMF can reduce pain, but is less effective than standard treatments. Furthermore, using it in addition to other standard treatment does not seem to increase the benefit.
Another approach to back pain management is to focus less on the pain, and more on the ability to carry out various tasks unimpeded. Some studies suggest that PEMF could reduce disability and the impact on the activities of living- while others call this into question.
Image credit: Woman photo created by freepik – www.freepik.com
An additional issue which may alter the effect of PEMF is that low back pain can be caused by a wide range of problems. Effects may indeed be different based on pathophysiology, but there are not enough studies to determine the effect of PEMF on each one. For example, the scoliosis gracing my back may cause pain that is more or less responsive to PEMF than arthritic pain. This could limit the strength of the evidence for low back pain in general.
It is also important to note that some of the studies on this topic were run by researchers with potential conflicts of interest. This, plus poor randomisation and/or blinding protocols could bias results. Small sample sizes and comparison of widely varying protocols also limits the general application of results.
In addition to its use for bone, joint and pain complaints discussed above Pulsed Electromagnetic Field (PEMF) Therapy could potentially benefit the brain and various other tissues
The popularity of PEMF for various health needs has slightly outpaced the evidence for it. However, as far as we know it is safe to use and can promote bone health. It may also help people with knee arthritis (and possibly arthritis elsewhere), low back pain and other sources of pain. To unlock the full potential of PEMF, we need research to give us a greater understanding of how PEMF works, and what are the optimal protocols for maximum benefit.
Have you used PEMF? Let us know how you found the experience!
Andrade, R., Duarte, H., Pereira, R. et al. (2016). Pulsed electromagnetic field therapy effectiveness in low back pain: A systematic review of randomized controlled trials. Porto Biomedical Journal, 1 (5): 156-163. https://doi.org/10.1016/j.pbj.2016.09.001.
Chen, L.; Duan, X., Xing, F. et al (2019). Effects of Pulsed Electromagnetic Field Therapy on Pain, Stiffness and Physical Function in Patients with Knee Osteoarthritis: a Systematic Review and Meta-analysis of Randomized Controlled Trials. Journal of Rehabilitation Medicine, 51(11): 821-827. https://doi.org/10.2340/16501977-2613
Galli, C., Pedrazzi, G. and Guizzardi, S. (2019), The cellular effects of Pulsed Electromagnetic Fields on osteoblasts: A review. Bioelectromagnetics, 40: 211-233. doi:10.1002/bem.22187
Geraets, C., van Beilen, M., van Dijk, M., et al. (2019). Lack of analgesic effects of transcranial pulsed electromagnetic field stimulation in neuropathic pain patients: A randomized double-blind crossover trial. Neuroscience letters, 699, 212–216. https://doi.org/10.1016/j.neulet.2019.01.051
Jeon, H-S., Kang, S-Y., Park, J-H., and Lee, H-S. (2015). Effects of pulsed electromagnetic field therapy on delayed-onset muscle soreness in biceps brachii. Physical Therapy in Sport, 16(1): 34-39. https://doi.org/10.1016/j.ptsp.2014.02.006.
Wu, Z., Ding, X., Lei, G. et al. (2018) Efficacy and safety of the pulsed electromagnetic field in osteoarthritis: a meta-analysis. BMJ Open; 8:e022879. doi: 10.1136/bmjopen-2018-022879
Yuan, J., Xin, F., and Jiang, W. (2018) Underlying Signaling Pathways and Therapeutic Applications of Pulsed Electromagnetic Fields in Bone Repair. Cell Physiol Biochem; 46:1581-1594. doi: 10.1159/000489206