IRCT2016120415932N12 IRCT 2017-01-07 Shiraz University of Medical Sciences The effect of core training using unstable sitting in patients with patrllofemoral pain syndrome The effect of postural control training using unstable sitting on knee joint pain and function in patients with patellofemoral pain syndrome 2017-01-20 anticipated 30 Complete https://irct.ir/trial/15043 interventional Randomization: Randomized, Blinding: Single blinded, Placebo: Not used, Assignment: Parallel, Purpose: Treatment. N/A Patellofemoral pain syndrome. Intervention 1: Intervention group: The same as control group plus postural control training exercise using unstable sitting. Patients will be asked to control their balance on unstable sitting and hold it as long as possible (3 set, 6 minutes). In order to progress the training, 3 unstable sitting with 3 different diameters (24, 30 and 50 cm) are provided. Intervention 2: Control group: Stretching exercises for quadriceps, hamstring, illiotibial band and calf muscles (3 repetition, 30 second hold); quadriceps setting, terminal knee extention, straight leg raise and hip abductor and external rotator strengthening exercise (3 set, 10 second hold).