During the clinch or just prior to the clinch the opponent very often throws knees to the torso area. I am not considering whether the opponent has managed to pull the head down for knees to head.
Putting an arm down to block is a bad idea for various reasons eg. lose balance and get thrown down. not having a guard against elbows etc.
What techniques/defense measures exist to block those knees from impacting on the torso (stomach/rib cage/ thighs/ hips)?