My data was a small part of an Australian study into musicians and injuries:-
Strad article on musos in pain
The results don't surprise me one bit - in fact I think they are conservative. One major issue that is not addressed in the article is that many musos will not admit to injuries for loss of a job or work. Take the case of a muso about to finish a trial for a job - they have just practiced their arse off to win the audition, then have been thro a prolonged period of pretty high stress and pressure on a trial, doing more practice than their counterparts who are not on trial.....all of which adds to the strain on the body. Are they going to admit to back twinge? Not on your life - that could well jeopardise them getting thro the trial and getting a job.
Its the same with free lancers - if you have a chronic condition I would like to think orchestras would still book you, and pay you if you had to take sick leave. But in this world of budget cuts I fear there is pressure to overlook injured players for younger, fitter musos who can get thro the work.
Its a tough world out there....but there is some help to hand, again from the Strad:-
The Strad - injury prevention