The Comparison of Hip Abductors with Hip External Rotator Muscles Fatigue on Static Standing Balance in Subjects with and without Patellofemoral Pain Syndrome

purpose: the patellofemoral pain syndrome (pfps) is one of the most common musculoskeletaldisorders of the knee joint. hip muscles’ weakness is one of the reasons for pfps occurrence.the aim of this study was to recognize the effective muscle group in prevention and treatmentof patients with pfps. methods: this is a prospective and quasi-experimental study in which 30 participants (15healthy/15 patients) who were aged between 18 and 38 years were recruited through nonprobabilitysimple sampling. exhaustion process of hip abductors and hip external rotatormuscles was performed using delorme method in separate sessions with a rest interval of atleast 48 hours. then, the parameters of pressure center were measured on the anterior, internalexternalplates using force plate system. results: before the exhaustion process, parameters of the displacement length of the pressurecenter on the internal-external plate (p = 0.002) and the sum of the pressure center displacementlength on the internal-external plate (p=0.052) were higher in the patients group. after theoccurrence of fatigue in the abductor muscles of the control group, the sum of the pressure centerdisplacement length on the internal-external plate (p = 00.1) and the velocity of the pressurecenter displacement length on the anterior plate (p = 0.001) and the internal-external plate (p= 0.016) were significantly increased. but in the patients group, all of the above mentionedparameters were decreased after fatigue in both the rotator muscles (p = 0.005, p = 0.054, p =0.038) and the abductor muscles (p = 0.045, p = 0.005, p = 0.004). conclusion: before the induction of fatigue, patients had more postural swing than thecontrol group. as the fatigue increased in the abductor and the external rotator muscles, thepostural swing increased in the control group but decreased in the patients group. in healthysubjects, the fatigue of abductor muscles has a greater role in postural disturbance but therewas no significant difference between the fatigue in abductor and rotator muscles in patientswith pfps.