Pain/discomfort in the knee?! ?

I always get pain in my knee whenever I'm sitting for a long period of times (like in the car or on a jet ski.) it's not intense pain it's more like a discomfort. I play soccer and It never hurts when I run or kick. It's my right knee which Is my dominant knee. My knee looks normal but I don't know what the pain can be cause by. I'm not sure if it's a small tear in a muscle or something. Any suggestions would be appericated. Thankyou!