Onset of quadriceps activation and torque variation during stair ascent in individuals with patellofemoral pain

Introduction: Studies have used surface electromyography (EMG) to understand motor recruitment in individuals with patellofemoral pain syndrome (PFPS); however, there is no consensus in the literature. Objective: To understand if, in addition to neuromuscular disorders, there are changes in rotational patterns in individuals with PFPS. Methods: Twenty-two control pain-free subjects and eleven subjects with PFPS were assessed during stair ascent with respect to the onset of muscle activation and percentage of torque variation (PTV). Result: The PFPS group showed previous activation of vastus lateralis (VL) (21.1 ± 58.1ms), while simultaneous activation was observed in the control group (2.8 ± 30.7ms, p=0.01). The groups also showed differences in relation to the PTV (p=0.02): the control group showed greater variation in torque (26.7 ± 35.3%) compared to the PFPS group (17.5 ± 35.9%). Conclusion: People with PFPS have prior activation of VL and lower tendency towards body rotation, which may suggest patellar lateralization.