Even though it's not my specialty, I'm like 99.9% sure it's patellofemoral pain or patellar tendonitis. It's a specific spot on the inside and lower part of my kneecap. There's a spot I can push on that hurts. It's right where the tendon inserts.
When I'm sitting here now, no pain. When I stopped running and walked, no pain. Most everything else, no pain. But with each running step, it grows from a feeling to an ache to worsening pain until I stop. I also feel it climbing up stairs or if I'm sitting and try to lift and straighten my leg at the knee. And that's only right now. Last week, as it got better, none of those things hurt at all except for running on it after a certain time. I otherwise had no idea anything was wrong.
It's an inflamed area for sure. It doesn't feel "damaged" and it's not a sharp or worrisome pain. But, both of those I listed above can be due to overuse and the best (and really main way) to fix it is rest. I'll do some ice, some stretching, some NSAIDs, but in the end, I just need to stop reaggravating it.
I'm an idiot because I took it easy last week and only ran 8 miles total but I would have been better off doing 0 and just eating the fitness loss. Now I've lost that bit of fitness and I'm no better off than I was when it started. I'm frustrated with myself for not being smarter about it even though I knew what I should have done. It's just that it would feel great for 3 days and I'd try and see if it was gone. At least I would stop each time I started feeling something which is probably why it gradually improved.
It was definitely getting better, though, and it really was great yesterday with no pain at all. But that workout flared it up because I felt it right away today despite running slowly. It didn't matter if I ran slow or fast today.
It'll get better.