Isometric strength measurements of knee extensors in women with osteoarthritis of the knee

Objective. To compare torque-angle characteristics of the knee extensors of women with and without osteoarthritis (OA) of the knee, and to determine the reliability of these measures. Methods. The isometric torque of the knee extensors of both legs was tested on 3 occasions in 17 women with OA of the knee and 17 healthy women. Tests were performed on an isokinetic dynamometer at 3 knee angles (30 degrees, 60 degrees, 90 degrees). The peak torque values were subjected to 4 way analysis of variance (group vs leg vs angle vs time), and intraclass correlation coefficients were calculated. Results. The reliability coefficients for repeated measures of isometric torque varied from 0.83 to 0.94 in the OA group and from 0.90 to 0.95 in the comparison group. The ANOVA and post hoc analyses revealed that the OA group had significantly (p <0.05) lower knee extensor torque than the comparison, group, and that the more symptomatic OA knee had lower torque than the contralateral limb. The torque was different across the 3 angles, but the torque-angle relationship was the same for both groups. Conclusion. Isometric torque of the knee extensors can be measured reliably in women with OA of the knee. The torque is lower in women with OA than in women with no knee problems, and the changes are similar across different knee angles.