Re: Former Athlete considering crossfit
If your shoulder flexibility/mobility is poor to average, be wary of the excessive kipping pullups/muscleups.
Back injuries? Umm, besides something like mixed grip 1rm DL just be mindful of some WOD's that go crazy on the backs. 50-40-30-20-10 Back Squats can be rough or stuff with with lots of GHD situps/raises.
Be mindful of Rhabdo or excessive DOMS to the point you can't bend your elbows enough to where you lose ROM.
Watch out for yourself because that's your first line of defense. Be mindful if something starts to feel wrong. Don't be a candyass, but don't **** yourself up for no good reason.
A lot of this really depends on whether you go to a CF gym "Box" to do CF or do it on your own.