Dynamic quadriceps muscle stimulation for treatment of patellofemoral pain

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Sadeh, Soroosh

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Introduction: Patellofemoral pain syndrome (PFPS) is one of the most common types of chronic knee pain. In order to treat PFPS, electrical stimulation (ES) is widely used. The primary goal of the present study was to investigate whether electrical stimulation of the vastus medialis oblique (VMO) and vastus lateralis (VL) to establish coactivation of these muscles during terminal swing phase of normal walking impacts factors associated with PFPS such as abnormal quadriceps muscle activation. Methods: Twelve persons diagnosed with PFPS participated in this study. Each participant completed four trials of normal walking. Each trial lasted for 6 minutes. VICON motion capture system was utilized to record the kinematic pattern of movement. VMO and VL muscles’ activity were recorded using mechanomyographic (MMG) technique. In order to electrically stimulate VMO and VL muscles, a wearable stimulator, “KneeStim (Articulate Labs, Inc.)”, was utilized. During trial one, participants walked without wearing the stimulator. During trial two, participants wore the KneeStim but the stimulator was off. During trial three, the stimulator was on at the beginning of each stride for the entire swing phase and electrically stimulated VMO and VL muscles of the symptomatic leg of the participant. Trial four was performed identical to trial two in order to observe the effects of stimulation on the muscles’ onset times. Muscle onset times as a measure of muscular activity pattern, stride length and stride period were compared over the entire experiment. Results: The onset times of the VMO and VL muscles showed significant change between trial one and trial two, and between trial two and four, but no change when trial one was compared to trial four. The difference of muscles’ onset times (VL-VMO) did not change after ES intervention. Stride period did not change, stride length (mm) values slightly decreased for symptomatic leg after participants were exposed to ES. However, this change was significant when non-symptomatic leg was taken into account. Conclusion: A single session ES intervention starting at the beginning of each stride showed earlier activation of quadriceps muscles during normal walking in individuals with PFPS. However, the delay onset timing of VL compared to VMO did not change after treatment.


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