Scientists find a protein block regrows knee cartilage in mice and human tissue

but there will be unintended side-effects with other muscle and organ growth that will be unacceptable

that protein sounds like nature evolved some kind of rate-limiter

but it's fascinating they found it

maybe it can be safely used for short spurts like a couple weeks at a time

(and I also bet it will become a performance-enhancing drug WADA has to test for)