Objective: We examined the relationship between isokinetic knee extensor strength and lower limb skeletal muscle mass measured by the impedance method. The objective of this study was to clarify the characteristics of knee extensor strength in patients with osteoarthritis of the knee.
Methods: The osteoarthritis (OA) group was composed of thirty-six lower limbs of twenty females with OA of the knee, and the control group was composed of fifty lower limbs of twenty five healthy females, respectively. The mean age of the OA group was 68.1±4.9 years and that of the control group was 70.3±3.6 years, respectively. We measured lower limb skeletal muscle mass by the eight electrode body impedance analysis (BIA) method. In addition, we measured the peak torque of the knee extensor muscle strength in 60 deg/sec. Investigations were also carried on primary lower limb skeletal muscle mass and knee extensor strength obtained from the control group. We then predicted the knee extension strength of the OA group, which was obtained using a formula.
Results: Lower limb skeletal muscle mass for the OA group was 6.2±0.6 kg, and for the control group was 6.3±0.5 kg (n.s.), respectively. Knee extensor torque for the OA group was 60.0±16.1 Nm, and for the control group was 77.7±13.7 Nm (p < 0.01), respectively. The primary regression equation in the control group was y = 11.016x + 8.63 (r = 0.428). Predictive value of knee extensor strength of the OA group obtained from the regression equation was 77.4±6.7 Nm.
Conclusion: The ratio of muscle output for skeletal muscle mass decreases in the patients with OA. Therefore, we think instead of simply increasing the muscle mass in the rehabilitation of patients with OA, it is necessary to continue to improve the ratio of muscle to muscle mass output.
