A NOVEL EXPERIMENTAL APPROACH FOR IDENTIFYING BIOMECHANICAL PARAMETERS ASSOCIATED WITH PATELLOFEMORAL PAIN: A CASE REPORT

PURPOSE: Individuals with patellofemoral pain may demonstrate asymmetries in muscle strength, influencing quadriceps strength and electromyographic (EMG) activity. These imbalances disrupt movement patterns and joint mechanics during weight-bearing activities, potentially compromising knee control and increasing patellofemoral stress. Observing these neuromuscular and kinematic alterations using biomechanical measurement methods might lead to a better understanding of effective management by objective evaluations. This study investigates the change of ground reaction force (GRF), knee valgus angle and muscle activation patterns of the quadriceps muscle group on the affected and unaffected sides in individuals with patellofemoral pain.METHODS: A 38-year-old right-dominant woman with right-sided patellofemoral pain participated in the study. Marker-based motion capture, a force plate and surface EMG were used to measure physiological, kinematic and kinetic parameters during a maximal isometric contraction at half-squat position. RESULTS: The muscle activation patterns at the affected and non-affected sides showed strong positive linear correlations (R > 0.84) with GRF-time history except for right Rectus Femoris (RF) (R: 0.61). The integrated EMG value of the right RF was less than that of the left RF, which aligns with the lower correlation. The valgus angle in the left knee was 5.7 ± 0.3 degrees higher than in the right knee.CONCLUSION: Muscle activation values on the affected side were lower compared to the non-affected side, while the valgus angle of the non-affected side was higher during isometric quadriceps loading. This finding indicates that compensatory mechanisms on the non-affected side may counteract the increased valgus motion on the affected side, potentially contributing to pain.