I'm not a doctor, and I don't play one on the internet, but I do have more than my fair share of experience with orthopedic and sports injuries (8 orthopedic surgeries so far...). Keeping aside the fact that Clemens hasn't exactly "acted" like an innocent person (given how long it took him to make a REAL statement, how he has been dancing around things, etc....), and that if McNamee's testimony/information to the Mitchell investigation was really under duress, it's certainly suspect, these are my thoughts...
I didn't watch Clemens on "60 Minutes" last night, for fear that I'd get so annoyed I'd throw things at the TV and get my blood pressure needlessly elevated. What I have seen of it, through clips on ESPN and such, don't really add up to me.
First, about the injections of vitamin B-12. We've heard it before, athletes claiming that they've been injected with vitamin B-12, in part (at least) to combat fatigue (it helps maintain healthy nerve and red blood cells). Last time we heard it, with Raphael Palmeiro, at least some of that "B-12" was probably steroids. Vitamin B-12 is commonly found in meats, particularly seafood and beef, so people with a normal diet should naturally get enough to cover the recommended daily allowance without supplements. For those who don't, my bottle of Centrum says that one pill has 100% the RDA of B12. Though it can be hard to get from foods, because it requires a few steps to be proceceed correctly, in supplement form, what you see is what you get. Why would somebody bother to inject it, even if they were trying to get more than the "normal" amount?
On another point, in the NY Times, it says that having the vitamin injected by a trainer is illegal in some states. I'm not sure if that means that it's illegal to have a trainer do it, or if it's illegal to have in the injectible form, or even what states it IS illegal (or legal) in. It's also stated that as an injectible, B-12 is given intravenously, but if it's been injected into the buttocks, that's hitting mostly muscle, not veins... It just strikes me as odd to get a vitamin which can easily be taken in pill form as an injection. But maybe he has a needle fetish?
As for the lidocaine, I'm much more skeptical, and this comes from a lot of personal experience with docs trying to keep me playing and keep me from going under the knife. Unless Clemens had a sore butt, there really would be no reason to inject lidocaine there. It's not a drug that acts systemically--it works only where you inject it. I've had it injected for "joint pain" only in the small joint in my hand. Though I've read that it helps if you have point pain in a joint, most of the other joints are too large to be treated by lidocaine injected into the joint (without multiple injections over the area), again, we heard from McNamee that he injected Clemens in the butt. Not in a joint.
The other way that lidocaine can be used for pain, in a more systemic matter, is to have it injected into a nerve. They do this before some surgeries (both of my shoulder surgeries were done with this method), and during/after some surgeries (in all of my ankle surgeries, I had it done to help with post-op pain management), and I believe it's sort of what pain management specialists do (based on my one visit to one). However, for a lot of the nerves in question, to find the nerve and ensure they're in the right place, the DOCTOR doing the injecting will first stick you with an electric needle. I know of at least one nerve where this isn't the case, but I also know of a few (from personal experience) where it definitely is the case. So it strikes me as highly unlikely that McNamee did THAT.
That all said, for longer-term joint pain management, most docs would I'm guessing recommend cortisone injections, and those are relatively easy to get from the team doc, it seems, so I think it's fairly unlikely that McNamee was injecting Clemens with those, especially given that injecting those incorrectly can cause other problems (I once had one go into a nerve...that was excruciating).
I'm highly suspicious of Clemens, and what he said on 60 Minutes only makes me more convinced that he's lying, or at least not telling the whole truth. In the end, it's going to turn into a he-said/he-said situation, and we may never have proof, but so far, color me skeptical...