I didn't see any leg workouts in the last three weeks of your training log, only some comment about knee pain.
What did your leg workout look like? The exercises, sets, and reps. Did you hit muscular failure on any sets?
Like the guys have said, of course you're going to have major DOMS when you start training a bodypart that isn't used to being trained. But as long as your training isn't dumb, the body will adapt and it'll soon be no big deal. Make sure you're eating enough, including workout nutrition (protein-carbs during training), to provide nutrients to recover with.