He mentioned that it had to do with "rich plasma therapy," which when he was originally talking about it, I thought it might be draining the knee, as some NBA players have had.
In researching "rich plasma therapy," I came upon
this article. DL said Mitchell was responding well to it, and that Mitchell told him he felt better after the procedure.
This is good news, and we'll see where it goes from here. It sounds similar to what Andrew Bynum had for the Lakers either last season or the season before, but he was playing at the time and he had the procedure between games.
Will post a link to this post from the Mitchell thread.