You're going strong, CS, as the season approaches.  Kind of sad, I suppose, that Clipperblog is just sitting around, not a care in the world, taking his sweet time to make that precision strike right to the heart of the Clipper conundrum.  You're like the bestselling novelist, say John Grisham, and he's J.M. Coetzee.  It's not fair!

But I digress.  I really didn't have a clue about what microfracture surgery was until recently, when I heard the part about making tiny incisions/whatever to stimulate growth.  But you're asking the real question.  I think I'd have to say that you're kind of skipping over how, back in the day, careers would simply end.  We remember the stars who limped back from major surgery (Baylor, Mantle, Sayers), but they were never the same, and a lot of guys probably just disappeared after they got hurt.  It seems as if certain star players were so great and gifted--Mantle, before the dh, not only could barely walk, he was also a major alcoholic, which isn't something you see every day in elite athletes anymore--that they could still compete with severely diminished skills.  But you always heard about how they were not nearly as good as they had been, that you should have seen them pre-injury.  Connie Hawkins comes to mind.

And Hawkins and Baylor are important to the discussion for another reason:  the game is played so differently.  Hawkins is credited with being the first player to play above the rim, although Baylor obviously got most of the way there.  Until Dr. J it was really Jerry West's game, jump shots, hooks and banks, not even 3's.  And so you could be a sky pioneer like Baylor or Hawkins and get grounded and still be effective and keep playing.  

So maybe it breaks down to elite guys who could still play after bad knee injuries, and guys who were on the cusp who just disappeared after they got hurt.

But the current surgeries and the injuries themselves are probably in part a result of how the game is now played.  Playing above the rim, with the athleticism, strength and speed that entails, must put added risk and stress on the knees.  Guys are going where players have never gone before--remember Bill Walton going nuts over Amare, saying he was a revolutionary big man?  Part of the problem seems to be mobility and speed, not just the vertical.  Whatever it is that makes Jason Kidd extraordinary (and it's not a Jerry West jumpshot), makes him end up with no knee I guess.

But all of this just makes your basic question more intriguing and elusive.  Greg Oden?  He just seems to be a very old young man.  What about Baron Davis, who is a lot like JKidd and had his own knee surgery coming out of UCLA--is he just saying no to microfracture and gutting it out, or is there some threshold of cartilege absence that he hasn't passed?  At any rate, I think that part of the answer to what happened in the old days is that the game is so different now, but I still don't get the basic elements of when this surgery is considered and why.

Really enjoyed reading this, ClipperSteve (and zhivclip's response, too).  Will chime in on some of the points you raise.

Yes, it's true that players often (and especially in previous years) turn to cortisone shots to play through the pain, saving the arthroscopic surgery for the off-season.  Especially the fringe guys who feel pressure to keep their spot on a team or are playing for a contract.  

But I'd contend that a lot these guys -did- drop off; the combo of cortisone and minimally invasive surgery might help them feel better, but their knees don't get any better long-term (if anything, they continue to degrade).  That's why a Ralph Sampson or Charles Smith lost their early promise, and a Jonathan Bender or Ed O'Bannon never really got started.  

Anecdotal example: In D.C., I vaguely remember how Lorenzo Williams--a rotation big man for the Wizards, who'd been a starter in Dallas--tried to use cortisone to play through his knee pain, and all he did was aggravate the injury.  As a result, Williams was placed on IR in early 1997 and never really made it back, with his time on the sidelines contributing to stress fractures when he did try to play again.
http://alumniatlas.com/players/nbaplayerpage.htm?ilkid=WILLILO01

So if you're an NBA player with a secure contract--and your body is your livelihood--you'll undergo microfracture because it's increasingly considered (despite fans' conventional wisdom) as the best way to get you practically all the way back.  And, in part, the growing trust in the procedure and advancements in medicine will ease physicians' ability to identify MF candidates and perform the surgery.  

It might seem like players like Greg Oden and Sean May are injuring their knees at younger and younger ages--which they may be, having played basketball year round for AAU, high school, and summer camp teams; as zhivclip notes, the increasing leaping and jumping component of the game places additional stress on the knee.  But small cartilage tears are like ticking time bombs, so more guys will get the procedure done earlier in their careers just to forestall potential damage down the road.  Twenty years ago, Spencer Hawes might just have been that tall guy who blew out his knee in high school; now, he has an NBA contract.

Not insignificantly, players also have increasingly doubted the wisdom of anti-inflammatories. Cortisone is considered relatively safe, but Alonzo Mourning claimed it helped contribute to his kidney disease.
http://query.nytimes.com/gst/fullpage.html?res=9C02E7D7133AF93AA15752C0A9649C8B63

The strides in medicine really are incredible, though.  I remember hearing Elgin Baylor interviewed about his bad knees; while he followed his doctors' rehab regimen in the 1960 to save his knees, in retrospect, he was doing a number of things we now know you're -not- supposed to do (heat versus ice, and so on).  I'm sure orthopedic surgeons will figure out something, in the relatively near future, that's far better than MF, but it really is the best procedure available right now.

That would be interesting.  Maybe you should run that study...

Note that while there are a few more teams today, you'd have to also normalize for the number of players coming into the league from Europe, South America, China, and so on--players may be able to play longer, but the spots might not be available.  I think a blogger (don't remember who) spoke to that point this summer, pointing out that a "full" NBA (as hardly any team had a roster spot available, yet a good 10-20 regular players from last year were still unsigned.)

Re: normalizing for 19 year-olds, it will be interesting to see how long Kobe, KG, and the rest last; they take so much more wear and tear, who knows if they're going to make it to 40, like a Karl Malone or Reggie Miller?