Does forward step-down task frontal kinematics differ in women with and without patellofemoral pain? A cross-sectional study

Purpose This study aimed to determine if forward step-down task frontal kinematics differ in women with and without patellofemoral pain (PFP). Methods Cross-sectional study. A total of 32 women were allocated into a healthy control group (CG; n = 16) and to a PFP ( n = 16) group. All participants performed two trials with five consecutive forward step-down task (FSD) repetitions each. A video camera, positioned 3 m from the participant’s frontal plane, recorded the movement (sampling rate = 30 Hz). All recorded videos were evaluated on Image-J software, and the following outcomes were obtained: delta mean (∆mean, the difference between final and initial positions) and delta peak (∆peak) values for Q-angle (Qϴ), hip and knee frontal plane projection angles, and dynamic valgus index. We compared groups with the Student’s t test for independent samples and the Mann–Whitney test. Results Groups showed similar ( p > 0.05) values for Q-angle (∆mean CG = 3.7° ± 2.5°, PFP = 3.2° ± 2.9°; ∆peak CG = 5.8° ± 2.5°, PFP = 5.1° ± 3.1°), hip frontal plane projection angle (∆mean CG = − 13.2° ± 5.4°, PFP = − 10.7° ± 5.3°; ∆peak CG = − 16.9° ± 5.1°, PFP = − 13.7° ± 5.2°), knee frontal plane projection angle (∆mean CG = -3.3° ± 4.5°, PFP = − 3.9° ± 4.5°; ∆peak CG = − 7.9° ± 6.7°, PFP = − 7.6° ± 5.2°) and dynamic valgus index (∆mean CG = − 17.2° ± 8.3°, PFP = − 15.0° ± 9.2°; ∆peak CG = − 19.4° ± 8.1°, PFP = − 17.3° ± 8.7°). Conclusion The similarity in frontal plane kinematics during FSD between PFP female patients and healthy women suggests that clinicians should be cautious when determining PFP presence in clinical practice with this method and when using it to measure a healthy condition to be achieved during rehabilitation. Trial registration Study was registered at Clinical Trials (NCT02734030) on Jan 1th of 2016 (retrospectively registered).