Medial-Lateral Center of Mass Displacement and Knee Adduction Biomechanics for Old and Young Adults Descending Stairs with Varying Surfaces

Introduction: Older adults (over 65 years) exhibit compensatory gait strategies, including larger, more variable medial-lateral center of mass (COM) displacement, during activities of daily living, such as stair descent. Larger COM displacement, however, reportedly increases knee biomechanics related to injury and disease. Yet, it is unknown whether older adults exhibit greater COM displacement when navigating stairs with a challenging surface, such as slick and uneven, or exhibit larger hazardous knee adduction biomechanics. Purpose: To investigate whether age and surface increase medial-lateral center of mass displacement, and the knee adduction angle and moment related to joint injury and disease. Methods: Twenty-nine (15 young – between 18 and 25 years; and 14 older – over 65 years) participated had COM displacement and knee biomechanics quantified during a stair descent on a normal, slick, and uneven surface. Then, maximum medial-lateral COM displacement, and magnitude and velocity of knee adduction angle and moment were submitted to RM ANOVA to test main effect and interaction between surface and age. Results: Surface (p = 0.005), but not age (p = 0.099) impacted medial-lateral COM displacement. Participants decreased COM displacement on the uneven compared to normal surface (p = 0.024). Surface impacted the average velocity of the knee adduction moment (p = 0.017), but no other knee adduction measure (p \u3e 0.05). Average velocity was larger on the normal compared to uneven surface (p = 0.035)