The Association between Lower Extremity Movement Patterns and Physical Function in People with Knee Osteoarthritis

Purpose: Explore the association between movement pattern variables and physical function (PF), compare movement pattern changes between standard and agility/perturbation training and explore the association of movement pattern changes with PF changes after an exercise program.Methods: Baseline evaluation was performed to collect subject characteristics, self-reported and performance-based PF followed by motion analysis and electromyography tests performed during gait and step down tasks. Subjects randomized into standard or agility/perturbation groups underwent 12 training-sessions. Post-treatment evaluation was performed at 2 months.Analyses: All analyses were performed for gait and step down task separately. At baseline stepwise multiple regression analyses were performed to explore the association of lower extremity kinematics and co-contraction with the Western Ontario and McMaster Universities Osteoarthritis Index -PF subscale (WOMAC-PF) and the Get up and Go test (GUG) separately. At post-treatment, comparisons of the changes in lower extremity kinematics and changes in co-contraction patterns between subjects who received standard versus agility/perturbation training were performed. Following, stepwise multiple regression analyses were performed to explore the association of changes in lower extremity kinematics and changes in co-contraction with changes in WOMAC-PF and changes in GUG. Results: At baseline results indicated that increased co-contraction during gait and step down were associated with poorer PF. The increased co-contraction of lateral muscle couples during gait was probably an attempt to control knee loading. The increased co-contraction of lateral and medial muscle couples during the step down was likely an attempt to avoid pain and instability as well as control loading at the knee. At post-treatment there was no difference in movement patterns changes between the two exercise groups. Increased co-contraction during gait was associated with improvement in GUG whereas during step down increased co-contraction was associated with worsening in WOMAC-PF. At both time points the observed associations of co-contraction with PF were likely a response to the unique constraints imposed by gait and the step down. We believe in order to improve patterns of movement and thereby improve PF in this population, rehabilitation programs may need to focus on specific practice of tasks which are difficult to people with knee osteoarthritis