Magnetic therapy uses ceramic ferrite magnets in dog or cat collars to treat pain from osteoarthritis or joint injuries.
A 2000 analysis of 31 clinical studies found, "The action on bone healing and pain alleviation of electromagnetic fields was confirmed in most of the trials. In the treatment of other disorders the results are contradictory."
A 2011 German study concluded, "The evaluation of 17 studies with static magnetic fields showed on average no significant difference in pain relief between the group treated with magnetic fields and the placebo group."
There are a number of magnetic therapy pet collars that are designed to help relieve painful joints due to arthritis or injury.