I can't recommend the rubber washers enough. Find them in the plumbing aisle at the hardware store. Buy a few packs cause you'll want to use more than 1 per knob.
Some knurled push-on type knobs can be a bit of a hassle to make hold them, but for the most part I haven't had to unwillingly adjust a knob since I started using them (and they still turn just fine when I want to adjust them).
Some knurled push-on type knobs can be a bit of a hassle to make hold them, but for the most part I haven't had to unwillingly adjust a knob since I started using them (and they still turn just fine when I want to adjust them).