There is no magic pill. Those injections were what allowed him to play and win slams despite his poor knees. If it weren't for those injections maybe his career or slam titles would've stopped in 2009 after he pulled out of wimbledon.
But there is a limit. Medical treatments can only do so much. nadal has definitley taken advantage of all the state of the art treatments there are out there.
You've got a point here.
The ONLY thing that may/might allow for tendon- and related cartiledge-like problems to heal is REST.
All of other 'treatments' is quackery.
I can only hope Rafa and/or his team has finally acknowledged this by now (though I won't be sure, knowing how much athletes are indeed susceptible to believing in all kinds of 'wonder medicine') and that he indeed allows himself all the rest to find himself a genuine recovery of his knees.