<prompt> All are features of patellofemoral stress syndrome are all exceptGiving way and then fallingChronic anterior knee painWorsening of pain with prolonged standingWorsening of pain on going upstairs.  <response>: Answer: a Giving way and then fallingPatellofemoral syndromeChondromalacia Patellae Patellofemoral pain syndromeDisorder of the patellofemoral joint presenting with anterior knee pain.Insidious in onsetExacerbated by activity involving strenuous or continuous flexionMore common in females than in malesSeen especially in the adolescent athleteMost common cause of knee pain in runners Associated ConditionsQuadriceps dysplasiaweaknessExtensor mechanism mal-alignmentPatellar instabilityRisk FactorsTraining errors e.g., rapidly increased mileageFemale genderPoor quadriceps strengthDysplastic vastus medialis obliquusGeneralized ligamentous laxityHeel cord and hamstring tightnessPatella altaExtensor mechanism malalignment increased femoral anteversion, increased Q angle, genu varumvalgus, external tibial torsion, pronated feetClinical features:Pain in the anterior knee, worse after strenuous and bent-knee activitiesPain with stair climbing, worse with going downPain after prolonged knee flexion, such as at theatres movie-goers knee or during long car ridesPain with squatting and rising from squatted positionPseudo giving-way of the knee 