Over the last 10 years, an average of 19.6 MLB players have gone down to TJ (ESPN has a list I averaged it). If we base numbers on approx. 345 MLB pitchers (11.5/team x 30), we get a 5.6% of pitchers falling to TJ @ the MLB level. Though if you have a 10 year career it doesn't mean you have a 56% chance of needing TJ surgery at some point afterall it's a 5% chance year after year but I'm sure how one looks after themselves, including their pitch counts, etc must highly relate to that outcome on a per pitcher basis.