west_side:
You can always find testimonials from people who will say "Yes. I pointed the crystal at my knee and it felt better." However, testimonials alone are never enough to prove that a treatment is effective. The placebo effect is an important one - people who are told they are being treated in some way tend to feel better, even when the "treatment" has no active effect. You can give somebody with a headache a sugar pill instead of an aspirin and they may feel better. And some illnesses just get better with time, regardless of treatment.
People often reason like this: "I took treatment X, then I got better. Therefore, treatment X made me better." But there might well be many good reasons why they got better which had nothing at all to do with treatment X.
My first reply to you is the important one here. There is NO scientific evidence that magnetic therapy of any kind actually has positive effects on health. No rigorous test has ever shown such effects.
Be very wary of people who have a vested interest in selling you a product. They are much more likely to exagerate the benefits, or even lie about them.