Knee Pain Help

So I've been having a lot of knee pain for the past few weeks, especially in my left knee. Doesn't hurt if I'm just sitting or standing but anything where I bend the knee (like going up stairs) was quite painful. The pain was mostly below the kneecap and only on the front of my leg. I thought I was just building up muscles there or something and didn't think I could do anything about it. But then last week I went to get a massage with my favorite masseuse and he said that my quad muscles were just super tight and they were pulling my knee muscles up and making them hurt. And the solution is as simple as stretching out those quad muscles more. Of course, I have been stretching my quad muscles during warm-ups, but apparently not enough, because once I started concentrating on those quad muscles, the pain totally went away. Yay!