Factors associated with greater co-contraction during walking and quadriceps exercises in patients with knee osteoarthritis

Background Patients with knee osteoarthritis exhibit greater knee muscle co-contraction, and which in turn is a risk factor for disease progression. Objective The aims of this study were to assess the muscle co-contraction during walking and quadriceps exercises in patients with medial knee osteoarthritis, and to identify the factors most associated with the alterations in co-contraction. Methods The subjects were 12 women with medial knee osteoarthritis and 13 asymptomatic controls. Kinematic and kinetic parameters during walking, and co-contraction indices during walking, knee extension and straight leg raising exercises were measured. The factors associated with the alteration in co-contraction in the osteoarthritis group were determined by linear regression analyses. Results Compared with the control group, the osteoarthritis group showed significantly greater co-contraction of the vastus lateralis and biceps femoris (VLBF) in two quadriceps exercises as well as the VLBF, co-contraction of the vastus lateralis and lateral gastrocnemius (VLLG) in walking. In linear regression analyses, the VLBF and VLLG in walking were associated with knee extension moment and knee pain frequency in daily life. The VLBF in knee extension and straight leg raising exercise were associated with knee flexion angle in a quiet standing position and knee varus peak angle during the stance phase of walking. Conclusions Greater muscle co-contractions were observed in not only walking but quadriceps strengthening exercises in patients with knee OA. Besides, the factors of these patterns were different in different tasks. These findings may help the development of more effective rehabilitation strategies for patients with knee osteoarthritis.