The main one is pain behind your kneecap. That really is the giveaway that something is wrong. You might have some pain from sitting, walking, or running for a long time. The pain is sometimes worse...
Your doctor will probably be able to tell you if you have it or not. That's how I found out about mine. I went in for a checkup and mentioned my knees had been hurting me latley. She measured my legs...
Many things can cause it to occur. They are:
overuse of the knee in sports and activities such as running and jumping
the way your hips, legs, knees, or feet are aligned
underdeveloped thigh...
It is basically a long name for the back of your kneecap hurts. Many people have heard of this even if they don't realize it. It goes by many different names. A few are chondromalacia, patellofemoral...