What do you mean by non Olympic weights? Are the weights you're using actually any smaller than standard weights?
I'd consider deadlifts a very safe movement for the knees. That being said if you're actually pulling from a severe deficit people commonly try and turn that into more of a squat motion. Which could have an effect. Not sure.
Do you deadlift with a heeled shoe? Or do you find your weight shifting onto your toes while you lift?