Alterations in lower extremity movement and muscle activation patterns in individuals with knee osteoarthritis.

OBJECTIVE: The purpose of this study was to investigate lower extremity movement and muscle activation patterns in individuals with knee osteoarthritis and healthy age- and gender-matched control subjects.
DESIGN: This study utilized a non-randomized case-control design to compare 24 subjects with unilateral symptomatic knee osteoarthritis to 24 age- and gender-matched control subjects without knee osteoarthritis.
BACKGROUND: It is hypothesized that knee osteoarthritis is associated with altered lower extremity movement and muscle activation patterns.
METHODS: A gait analysis was performed to determine the lower extremity movement and muscle activation patterns when walking on a level surface at 1.12 to 1.34 m/s and while descending a 20 cm step. Paired t-tests were used to compare the average of five trials between the groups.
RESULTS: Subjects with knee osteoarthritis demonstrated less excursion of the knee in the sagittal plane from heelstrike to peak flexion before midstance (i.e. during loading). Subjects with knee osteoarthritis also demonstrated reduced peak vertical ground reaction forces relative to body weight. The muscle activity patterns were also different between the groups. The vastus lateralis, medial hamstrings, tibialis anterior and medial gastrocnemius were on approximately 1.5 times longer than the same muscles in the control subjects. Additionally, significant increases in muscle co-activation were also observed in individuals with knee osteoarthritis during walking. Similar findings were observed when the subject descended a 20 cm step.