I've had knee pain on my left knee for the past 3 to 4 years. I got hurt while performing squats without warm-up and ever since my knee hurts. The pain isn't constant. Sometimes it goes away for weeks at stretch but then lingers back, stays for about a week and goes away again. Movements like squatting down makes it worse. Intensity of the pain is between moderate to severe when it lasts. What could be the possible cause and cure? Any help would be appreciated. Thanks