you have to provide more detail info such as your age, when did pain start and which area of the knee? did you have prior injury to this knee? how long have you had this pain. does your knee lockup or buckle? when does this, occur?only when playing soccor or w/other times as well?
You might have a slight tear in your meniscus. It's the "shock absorber" part of the knee and sometimes they tend to start small and get wider. It's a routine surgery and only an MRI will tell how to diagnose and treat properly.