Context: Patellofemoral pain syndrome (PFPS) is a maltifactorial knee condition. It has been suggested that alteration in hip musculature activation and excessive knee valgus are two of the major contributions to PFPS. However, the influence of hip muscle activation and knee kinematics during dynamic activity has not been explored fully. Objective: The primary purpose of this study was to compare hip and knee muscle activities and frontal plane knee kinematics during the anterior direction of the Star Excursion Balance Test (SEBT) between a PFPS group and a healthy group. The secondary purpose was to determine whether pain level and performance as measured by the reach distance of the dynamic postural control task may be associated with PFPS. Design: Case-controlled cohort study with repeated measures for the VAS. Setting: Athletic training research laboratory. Patients or Other Participants: Twenty eight subjects participated in this study and completed the test (14 PFPS: Age= 21.07±3.27yrs, Ht= 172.09±10.26cm, Mass= 69.96±9.05kg; 14 Control: Age= 20.93±3.00yrs, Ht= 170.18±8.94cm, Mass= 70.25±8.57kg) Subjects with PFPS reported minimal 2 months of anterior or lateral knee pain with walking, running, ascent and descent of stair climbing, kneeling, squatting, and sitting for long periods of time. Interventions: Participants performed 3 maximal voluntary isometric contractions (MVIC) in hip abduction, extension, external rotation, and knee extension and 5 anterior reaches of the SEBT. Main Outcome Measures: Frontal plane knee kinematics, anterior reach distance during the SEBT, and normalized average electromyography (Norm Avg EMG (%MVIC)) of the gluteus maximus (GMax), gluteus medius (GMed), and the vastus medialis (VM) were measured. In addition, knee pain was assessed with the Visual Analog Scale (VAS) before, during and after the task. Results: Comparing to the control group, PFPS group demonstrated increased knee valgus angle at touchdown, the point of the maximum reach (p=0.047), and significantly less varus displacement during the SEBT (p=.011). When observing the anterior-direction SEBT, reach distances were significantly shorter in PFPS group compared to the healthy group (p=.014). For pain on the visual analogue scale (VAS), there was a statistically significant group by time interaction for VAS (F 2,52=4.70, p<.001). PFPS group demonstrated significantly increased pain at pre, during, and post tasks. In addition, subjects with PFPS demonstrated significantly increased pain during and post tests compared to pre test, and increased pain during test compared to post test. There was a statistically increased VM normalized average EMG in the PFPS group compared to the control group while there was no statistically significant difference in the iEMG of the gluteus medius and gluteus maximus between groups. Conclusion: The results derived from our study indicate that PFPS subjects demonstrate increased knee valgus angle in the anterior reach task on the SEBT. In addition, the PFPS group demonstrated shorter reach distance on the SEBT, along with increased pain on the VAS. On the contrary to our hypothesis, subjects with PFPS demonstrated greater VM activities than healthy subjects. In the sagittal plane movement, VM may play an important role to maintain the balance, while GMed and GMax may not be the primary muscle for the postural control during the task. During a common sagittal plane rehabilitation activity, it may be important for clinicians to observe differences in frontal plane positioning at the knee with PFPS.
|Commitee:||Armstrong, Charles, Mcloughlin, Tom|
|School:||The University of Toledo|
|School Location:||United States -- Ohio|
|Source:||MAI 57/05M(E), Masters Abstracts International|
|Keywords:||Electromyography, Emg, Knee valgus, Patellofemoral pain, Pfp, Pfps|
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