The most common causes are: Patellofremoral pain-this is mainly an injury felt at the front of the knee but can also cause symtoms on the inside of the knee. Medial meniscus tear-is a tear or degeneration of the semi cicular cartilage discs found in the knee joint.he most common causes are: Referred pain-which can come from an injury or problem in the lower back, front of the knee or other nerve problem in the hip of buttocks. Biceps femoris tendinopathy-which is inflammation or degeneration of the tendon of one of the hamstring muscles as it inserts into the back of the knee.