Pulsed electromagnetic fields in knee osteoarthritis: a double blind, placebo-controlled, randomized clinical trial.

Bagnato GN et al Rheumatology (Oxford). 2016 Apr;55(4)

This was a scientifically rigorous test of wearable pulsed electromagnetic fields (PEMF) for older patients with osteoarthritis of the knee: moderate to severe cases with X-ray evidence and pain of at least 4/10 for more than six months, despite maximum tolerated medication. PEMF is particularly easy to test properly, because it causes no sensation, making it much easier to compare to an active placebo. The placebo devices do not emit a radiofrequency electromagnetic and the active device cannot be distinguished in any way from the placebo device.

Their pain and knee function were compared. PEMF won decisively: the real-PEMF patients enjoyed a 25.5% reduction in pain, compared to a 3.6% reduction for the fake-PEMF patients. Knee function improved as well, though not as much.
The authors explain that “some of the effects of this therapeutic approach might be derived from neuromodulation of the pain mechanism”: that is, it might be “just” a pain-killer, as opposed to actually helping to heal arthritic cartilage.