I've been doing yoga for the past couple weeks. And on the whole, it's making me feel better and improving my terrible posture.

But I get a really sharp pain in my left knee during a couple of poses. Knees/Chest/Chin is mostly okay, but I have to ease into it, and maybe adjust. But if I land/set up wrong, it hurts.

But low lunge will hurt 90% of the time. And it's a really sharp, intense pain. Localized, but makes me feel like I can't support myself.

Randomly poking around before or after doesn't seem to trigger anything. When I'm not in the poses, the pain goes away very quickly. For a short period of time, the center of the kneecap, and the bottom are tender immediately afterwards-but only when poking&prodding&sliding.

This happened the first time I did yoga a couple weeks ago. I've mostly been avoiding those two poses, but tried it again tonight and it's just as bad as ever. It's only one knee(left), and no trauma that I can remember. Certainly nothing recent. Maybe a couple falls hiking in the early spring this year or last year.

My activity level has been streaky this year, but no issues when I was running every day for 3 months, or cycling ~100 miles a week for the past 5 weeks. No issues when I was lifting weights either.

What gives?