So I've had a couple torn muscles in my right knee, nothing too major. My left knee however has been crashed on several times and put me off the bike for a few weeks in the past. But each time I have had a knee injury, it could usually be tied to something, like a crash, or a sketchy landing. I was riding park a few weeks ago, and towards the end of the 4 hour session, my right knee (the good one), started to become a bit tight and painful when I straightened it. I hadn't crashed all day, the only time I was straightening my knees was when I was trying to keep my front wheel in the air in a manual. It was really sore the rest of that night on through the next day.The pain was coming from directly behind my knee, right above the calf, each time my leg was extended, or when my knee was completely bent. So I stretched a bit and put a heating pad on it. The next day it felt better. After about 5 days it felt fine so I hopped back on the bike for a quick little park session, and boom it started hurting again. I haven't ridden since, (about a week and a half ago), but it is still as sore as it was the day after it started. I did some research and the location of the pain matches up to a hyper-extended knee, but there hasn't been any swelling. The only other symptom besides that is sometimes when my knee is fully straightened, it feels almost locked and for a split second it doesn't want to unlock. Usually when I lean over something and try to bend my knee. I am not totally worried because it's not excruciating pain, more like burning muscle pain. It is just lasting a bit longer than a simple pulled muscle. So any advice would be nice, thanks monkeys.