Background and Aim: Patellofemoral pain syndrome (PFPS) is among the most common musculoskeletal disorders in the athletes and active individuals. Observation of muscular responses to unexpected perturbations is one of the most common methods to evaluate the neural strategies. The aim of this study was to evaluate the EMG response of vastus muscles to dynamic postural perturbations in the athletes with PFPS.

Material and Method: This study included 10 male athletes with PFPS and 10 healthy male athletes. NPRS scale was used to assess pain. EMG activity of VMO and VL muscles measured during dynamic postural perturbation. The EMG signals were collected using a 16- channel BTS-FREEEMG 300 system, manufactured in Italy. Independent-t test was used for data analysis.

Results: RMS values for VMO and VL muscles in PFPS group, were higher than the corresponding values of the control group by 33.59% and 33.35% respectively, in the forward postural perturbation. There was a significant difference in VL muscle RMS values between the two groups (P=0.04). RMS values for VMO and VL muscles in PFPS group were higher than those of the control group by 38% and 49.52% respectively, in the backward postural perturbation and there was a significant difference in VL muscle RMS values between the two groups (P=0.04).

Conclusion: The results showed that valtus muscles were more active in response to dynamic postural perturbation in the athletes with PFPS in comparison to the healthy athletes. Patellofemoral pain syndrome and in general joint disorders can lead to dysfunction in the whole sensory-motor system. Therefore, instead of focusing on local symptoms we should examine the whole body in sensory-motor system dysfunction.

Key words: Electromyography response, Postural dynamic perturbations, Patellofemoral pain syndrome, Vastus muscles.

Received: Apr 11, 2016      Accepted: May 17, 2016