Can magnets cure knee pain?

Almost every sporting goods store, pro-shop or web page has an advertisement for therapeutic magnets with claims of pain relief and a better golf game. There are magnetic bracelets, necklaces, shoes inserts, mattress covers, head bands and, yes, dog collars. It certainly isn’t new. But, is there any scientific evidence to support all of these claims?

We can go back to 16th century Switzerland and find Greta who is beyond worried about her teenage son. She works the fields every day, keeping a watchful eye on her son as he digs at the stubborn ground just two rows to her right. Will he have another one of his “fits” today: falling to the ground, muscles tightened and mouth clenched shut? She had heard a rumor that the alchemist, Paracelsus, was taking the “magical” lodestone, a type of ore that could attract iron, and grinding it into a powder, placing it into a salve and applying it to the bodies of sick people with miraculous results. Would the lodestone pull out the poisons that possess her son? She was willing to try anything.

If magnets work, they must have some physiological effect on the human body. They must, in some way, influence the tissue, cells, fluid or blood over which they are applied. Advocates for magnetic therapy have proposed a number of ways in which the magnets work on our bodies.

Blood Flow: Many ads and brochures claim that blood contains iron and that magnets increase blood flow under the area where they are applied and promote healing. Although blood does contain electrically charged ions, it is diamagnetic and strong magnets actually repel blood. Another problem is that the effect of surface magnets is too small to affect blood flow and overcome the pressure-driven turbulent flow of normal blood. As a simple experiment, place one of these therapeutic magnets in the palm of your hand. If blood flow actually increased, you would expect the skin around the magnet to pink up and become warm. It doesn’t. 

Fluid and Swelling: Others claim that the magnets line up the water molecules in our bodies and, in this way, decrease swelling and promote healing. However, even large magnets like those used in an MRI scanner do not line up water molecules. A typical surface magnet is 800 Gauss; a Gauss unit representing one unit of magnetic field density. An MRI scan magnet generates 30,000-40,000 Gauss and yet has not been shown to have any biological effect on humans. If they did, they would have serious restrictions on their use.

Nerve Conduction: Some manufacturers claim alterations in the way that our nerves and nerve cells conduct electricity. But, it takes a large 24 tesla magnet to decrease nerve conduction velocities by only 10 percent. The typical MRI scanner uses a 1-1.5 tesla magnet, where one tesla equals 10,000 Gauss.