Purpose: The study's purpose was to compare trunk, pelvis, hip, and knee frontal plane biomechanics in males and females with and without patellofemoral pain syndrome (PFPS) during stepping.
Methods: Eighty recreational athletes were equally divided into four groups: female PFPS, female controls, male PFPS, and male controls. Trunk, pelvis, hip, and knee frontal plane kinematics and activation of the gluteus medius were evaluated at 15°, 30°, 45°, and 60° of knee flexion during the downward and upward phases of the stepping task. Isometric hip abductor torque was also evaluated.
Results: Females showed increased hip adduction and knee abduction at all knee flexion angles, greater ipsilateral trunk lean and contralateral pelvic drop from 60° of knee flexion till the end of the stepping task (P = 0.027-0.001), diminished hip abductor torque (P < 0.001), and increased gluteus medius activation than males (P = 0.008-0.001). PFPS subjects presented increased knee abduction at all the angles evaluated; greater trunk, pelvis, and hip motion from 45° of knee flexion of the downward phase till the end of the maneuver; and diminished gluteus medius activation at 60° of knee flexion, compared with controls (P = 0.034-0.001). Females with PFPS showed lower hip abductor torque compared with the other groups.
Conclusions: Females presented with altered frontal plane biomechanics that may predispose them to knee injury. PFPS subjects showed frontal plane biomechanics that could increase the lateral patellofemoral joint stress at all the angles evaluated and could increase even more from 45° of knee flexion in the downward phase until the end of the maneuver. Hip abductor strengthening and motor control training should be considered when treating females with PFPS.