There is no system that provide credentials that anyone can use and trust as meaningful.
But the buyer can use simple ways to see what happens. Talk to students, for exmple if they're all limping that might point to the knee hyper-extension you mention. Sure that's simplistic but there is little else. Find knowlegable individuals and solicit their opinion, compare schools, and then keep a commitment if when you get into the program if it is bad, leave immediately. Document your reason and when they come after you for money, counter sue!!!!!!!!!!
Pleasant world isn't it.
The rule Crevat Emptor, let the buyer beware, is the true credential.
bushi no te isshinryu
offering free instruction for 30 years