Originally Posted by 5kgLifter
Consider that it's not always a heavier weightload that causes knee pain/discomfort, it can also be high repetitions; though you are using lightweight for the DB squats, you still have to raise over 75% of your bodyweight in each squat as well (in the form of everything above your calf) and it looks like you're doing between 50-75 reps on squats each time.
Your cardio, depending on what it is, will also affect the knees, put those two together (high reps and cardio) and your knees are going to feel it, eventually.
It may be wise to drop from the 30 reps in your first set and have two more reps in a lesser set but with more load etc. You need to make the routine work for you and doing lots of reps with a light weight may just end up burning your knees out before you get to doing the heavier loads.
Just my opinion, certainly no expert though.
Thanks 5kglifter, I will incorporate this today itself. And actually, even I felt it after so many reps.