Comparative Evaluation of Core Muscle Recruitment Pattern in Response to Sudden External Perturbations in Patients With Patellofemoral Pain Syndrome and Healthy Subjects

ObjectiveTo evaluate the core muscles' electromyographic activity in response to unexpected perturbations to the pelvis in patients with patellofemoral pain syndrome (PFPS) and healthy subjects.DesignCase-control study.SettingCenter for human motion science research.ParticipantsWomen (N=54) aged 18 to 40 years, including 27 subjects with diagnosed PFPS and 27 healthy controls.InterventionAn unexpected perturbation was applied to the lateral side of the pelvis by pulling a 1kg medicine ball back to an angle in which releasing the pendulum applied the energy of 20% of the subject's body mass index. This intervention was repeated 3 times with a minimum of 30 seconds of rest between the trials.Main Outcome MeasuresElectromyographic onsets and durations of the transversus abdominis/internal oblique, erector spinae (ES), and gluteus medius (GM) muscles were recorded in response to the unexpected lateral perturbation to the pelvis.ResultsThe recruitment pattern of the core muscles was different between the 2 groups. In the subjects with PFPS, the abdominal muscles and the ES activated significantly earlier and longer, whereas the GM responded significantly later than in the controls. The duration of GM activity was not significantly different between the groups.ConclusionsThe results of this investigation suggest that the core muscles are recruited differently in subjects with PFPS to provide core stability. It appears that core neuromuscular improvement could be an effective strategy in rehabilitation of patients with PFPS.