I was sitting down at the computer and touch my knee, I got type 2 diabetes and in my early 30's. Anyway, I bent down and felt my left knee cap directly above where the front of my calf starts, there is a deep 'depression.' It's like a sunken in part, other kneecap isn't like this. There is no pain. Is this and what cause it? :( ty.

Could just be wear and tear,I have something similar on my left knee but I also have aches with it sometimes,this will be because I tend to kneel down on this one more than the other.
You say you have no pain, so it could be anything,if it worries you then I would pay a visit to my GP who probably will send you for an exray if he thinks it's necessary.

Ty. Glad someone finally answered!

There are apiece of bone call patella cover the front of knee joint.This bone is holding by tendon connect to muscles.The position of this bone is depend on the muscle tone of this holding muscles.Sometime the strength of this muscles or tightness of some tendon change.This bone will be pull down and create the "depression" as you say.If this joint function well don't worry.

There are a piece of bone call patella cover the front of knee joint which is holding by tendon connect to muscles.The position of the bone are depend on the muscles tone and tightness of those muscles and tendon.For some reasons the muscle tone and tightness of those tendon change and result the bone pull down and create the "depression" as you say.As long as this joint function well and no histroy of injury will be OK,When you next visit to your doctor ask he/she for evaluation.