North
Molybdenum may chelate copper (or, may remove copper from the body in some way). I've seen hints/arguements that it does and that it doesn't.
And, copper is needed for healthy cartilage in the body. Most people (but not all) have too much copper and would want to lose some of it, but maybe you don't have enough copper.
Or to open a bigger subject, google biounavailable copper. Then it gets really complex.