Knee Pain

i've just developed (since my last ride 10 hours ago) some knee pain only on my left knee. i can feel the muscle/tendon/medical word mving when i bend my knee. i felt it a little bit earlier in the week but thought nothing of it. anyone else had this? it might be an old skateboarding injury playing up.

Is your natural skidding position right foot forward? or are you ambidexterous?