Thanks.
All the people I have seen get hurt were us older ( in their 40's) folks and it was usually a culmination of many years of problems with a particular joint. One of my good friends from class tore his shoulder up and had to have rotator cuff surgery, but he had injured the same shoulder years ago playing rugby when he was young.
I have had problems with my left knee since Army basic training when I wrenched it, and one night during a very physical sparring match, my ACL tore. I had seen doctors over the years for random swelling/pain in that knee on occasion, but no diagnostic tools were used on it other than an x-ray(which cannot tell you shit about a ligament injury).
When I injured it 20 something years ago, there were no MRI's or that stuff, so I don't know what damage was done internally to the joint, so it may have been a ticking time bomb.
I've never seen a kid get hurt in a class, they seem to be made of rubber or some other very durable substance.
Almost every injury happened during physical sparring, and some due to incidental contact. It happens.