Here's another article from nadalnews.com.
This one sounds encouraging, I think.
http://www.nadalnews.com/2013/12/30/its-a-good-knee-new/#more-49794(Doha, December 30 DPA.) – For the first time in more than two years, Rafael Nadal feels no pain in his knees. A stem cell treatment completed a few weeks ago allows him to face the season with renewed optimism, after he got to regain the number one in the previous season playing with antiinflammatories for a big part of it.
“It’s too early to know how definitive is the treatment, because I’ve only been working for three weeks. But it’s the first time in more than two years that I have no pain in the everyday life”, Nadal said in Doha.
The Spanish tennis player revealed his renewed confidence in his punished knees in the press conference prior to his participation in the tennis tournament in the capital of Qatar, which began today and where tomorrow he will make the debut against the Czech Lukas Rosol.
In previous years, Nadal had platelet rich plasma injected, which the player considered as “potentially crucial” to save his career.
The use of stem cells now facilitating the recovery of his cartilages is a novelty that his team decided to incorporate at the end of the last season, in November, and so far the result is excellent, although Nadal was unable to give precise details of the nature of the procedure.