Synergetic and Antagonist Muscle Strength and Activity in Women With Knee Osteoarthritis

Patsika, Glykeria MSc; Kellis, Eleftherios PhD; Kofotolis, Nikolaos PhD; Salonikidis, Konstantinos PhD; Amiridis, Ioannis G. PhD

Journal of Geriatric Physical Therapy: January/March 2014 - Volume 37 - Issue 1 - p 17–23
doi: 10.1519/JPT.0b013e31828fccc1
Research Reports

Background and Purpose: People with knee osteoarthritis (OA) display limitations in daily activities and a lower quality of life. The purpose of this study was to investigate the differences in strength balance and activation during maximum strength efforts between women with knee OA and asymptomatic women.

Methods: Twelve women with knee OA (age 60.33 ± 6.66 years) and 11 controls (age 56.54 ± 5.46 years) performed maximum isokinetic eccentric and concentric knee extension and flexion tests at 60°/s, 120°/s, and 150°/s. Surface electromyography (EMG) was recorded from the biceps femoris (BF), vastus lateralis (VL), and vastus medialis (VM). Hamstrings-to-quadriceps moment ratios (H/Q), the synergetic (VL/VM), and co-contraction (BF/[VM + VL]) EMG ratios were calculated.

Results: Analysis-of-variance designs showed that women experiencing knee OA had significantly higher H/Q moment ratios and VM/VL EMG ratios than controls (P < 0.05). The co-contraction index was significantly lower in the OA group only during knee flexion (P < 0.05).

Conclusions: Women with knee OA showed a higher H/Q moment ratios probably because of the need for better joint stability or a lower quadriceps capacity. This deficiency was accompanied by a higher VM activation, which probably serves to stabilize the patella upon maximum contraction as well as a higher activation of antagonist muscles.

Laboratory of Neuromechanics, Department of Physical Education and Sports Science of Serres, Aristotle University of Thessaloniki, Greece.

Address correspondence to: Glykeria Patsika, MSc, Laboratory of Neuromechanics, Aristotle University of Thessaloniki, Department of Physical Education and Sport Sciences at Serres, 62110, Serres, Greece (

There are no conflicts of interest and no source of funding.

© 2014 Academy of Geriatric Physical Therapy, APTA