I’m 20 years old..pretty active and I’ve had problems in my left knee about 3 years ago…and physical therapy fixed it. It was never a lot of pain, only a little discomfort. Now my right knee is hurting so badly its brought me to tears a couple of times this morning. It hurts when i walk, definitely when i go up and down stairs, if i keep it bent too long or straight too long it gets very achy. It’s a very sharp deep pain all through my knee cap, mainly at the top towards the left side of the cap. I dont think i’ve injured it…but my mom wants me to try working out my quad to strengthen my knee, but its hurts so bad that i cant. Is it time to go back to the doctor..what could it be?