Of course conformation flaws and improper training can/will break a horse down. My point was simply that NOT all horses getting joint injections or on joint supplements currently have a problem. Many view such treatments/supplements as preventative maintenance. That's how I view my own sports massage, well, except that I'm old and creaky and do have aches and pains, but I digress.
Look very carefully at the performance/work history of the horse in terms of the injections and the colic.
Unpopular as it obviously will be on his thread, I'm with PSJ on hock injections - conformation flaws, training flaws greatly contribute; it is NOT a given that upper level dressage horses will/should have hock issues