Movement patterns are different but muscle activations are unchanged in women with patellofemoral pain

Abstract

Patellofemoral pain (PFP) is one of the leading causes of knee pain. Changes in movement patterns and a possible relationship between movement patterns and muscle activation are commonly found in women with PFP [1]. The Movement Deviation Profile (MDP) showed differences in the movement pattern in women with PFP [2], however, to the best of our knowledge, the MDP was not used to differentiate the electromyography of women with and without PFP. This study aimed to verify whether the combined analysis of kinematics and EMG data increases the ability to differentiate between women with and without PFP compared to the independent analysis of kinematics and electromyographic activity. Is there a difference in movement patterns and muscle activation between women with and without PFP? Could the combination of EMG with kinematics data increase the ability to differentiate women with and without PFP? Seventy-one women, 37 with PFP and 34 unimpaired were selected for kinematic and EMG evaluation during the Lateral Step Down (LSD) task. For the 3D kinematics, movements in the sagittal, frontal and transverse planes of the trunk, pelvis and hip were used; sagittal and frontal planes of the knee; ankle sagittal plane; and the transverse plane of the foot in relation to the laboratory. For the EMG, filtered, rectified and smoothed signals from the adductor longus, gluteus medius, vastus lateralis and medialis, rectus femoris, biceps femoris, medial gastrocnemius and tibialis anterior muscles were used, which were normalised in amplitude to the average of the peaks of each cycle of LSD and in time by resampling the EMG envelopes every 1% of the LSD cycle. The MDP, which is a single number measure of movement deviation derived from a multidimensional neural network analysis, was used to analyse kinematics, EMG and kinematics combined with EMG. The Z-score of the MDPmean was calculated to compare the standardised results between women with and without PFP. A multivariate analysis with Bonferroni post-hoc test compared the groups considering p < 0.05. Multivariate analysis showed group interaction (l=0.838; F=4.329; p=0.008). There was a significant difference between groups in the MDPmean Z-Score only for kinematics (0.97). There was no difference between groups for EMG (0.44) and kinematics with EMG (0.39).Download : Download high-res image (117KB)Download : Download full-size image This study corroborates with the literature demonstrating that women with PFP present changes in the movement pattern but not in the amplitude of the electromyography. EMG, even when evaluating with a self-organising neural network (MDP), considering several muscles relevant to PFP, failed to differentiate between women with and without PFP both on its own or combined with kinematics. We conclude that, when using MDP, kinematics is the variable capable of differentiating women with and without PFP during LSD.