I have gone from walking about half an hour a day, to jogging only about 2 km's, with walk stops, so I'm new at this. When I jog, everything feels fine, but when I wake up in the morning, my left knee is killing me (right knee is fine). It's bad to the point of me limping. When I walk for a bit, I can feel it getting better, but if I sit even for a minute, it starts to really hurt again when I get up - it's like when it's not in use, it locks up. It will hurt for days, and it's not even swelled up. I've never had knee/leg problems whatsoever in my 23 years, no surgeries or anything! It this so serious I need to see a doctor, or should I wear a brace? I'm baffled as well why only one leg is giving me so much pain! Please help, thanks a lot!