When you twist your leg around your opponent’s leg and just collapse your body on your opponent, you will hurt his knee joint sideway badly.
I never had any injuries from simply practicing movements/postures like low stances, kicks, strikes, falls, etc. I’ve been training regularly for 34 years now. That said, I have been dealing with challenges from some non-MA related injuries from a few years ago.
The worst injuries I’ve had in MA training was one to my thumb joint, when somebody blocked my right hook to the body with his elbow; an over-cranked neck; a few concussions; jammed fingers and toes; and one time I somehow managed to rip my thumbnail completely off while practicing with a spear, practicing a thrusting movement carelessly. That’s about it.