These studies focused on patellofemoral joint pain and had conflicting results concerning the relationship between vastus muscles activity and the onset of pain on abnormal patellofemoral joint function.PFPS has a multifactorial etiology with factors ranging from unsuitable playing surfaces and overtraining, to skeletal alignment abnormalities, to poor neuromuscular control of the lower extremity. The connection among these factors is that they all assumed to alter the tracking of the patella within the trochlear groove. Proper tracking requires balanced forces acting on the patella.Adequate history taking in patient with patellofemoral pain will provide information that will suggest a likely diagnosis. The patient usually complains of vague pain or discomfort around the kneecap but frequently is unable pinpoint the specific pain. Symptoms are worsened with activities requiring a flexed knee, prolonged sitting, downhill running and stair climbing.Patellofemoral pain usually increases with activity and decreases with rest. The pain is rarely constant and asymptomatic periods are common.