Abstract
Introduction: Hand-held isometric dynamometry is a convenient alternative to gold standard isokinetic dynamometry for the assessment of skeletal muscle strength. The purpose of this study was to quantify the absolute and relative reliability of hand-held dynamometry, for the measurement of lower-limb isometric strength in patients with severe hip and knee osteoarthritis, scheduled for total hip or knee replacement surgery. Methods: Forty participants with severe osteoarthritis scheduled for hip (n = 20) and knee (n = 20) replacement were included in this retrospective cross-sectional analysis. Isometric muscle strength was assessed using a Microfet2 hand-held dynamometer for knee extension and flexion and hip abduction and extension. Absolute reliability was calculated using standard error of measurement and minimal detectable change and relative reliability was determined by intraclass correlation coefficient. Results: Standard error of measurement values ranged from 4.4-6.9 N for hip abduction and extension in the hip osteoarthritis group, and 4.1-11.4 N for knee extension and flexion in the knee osteoarthritis group. The minimal detectable change values ranged from 15.4-24.3% of maximal voluntary contraction for hip abduction and extension in the hip osteoarthritis group, and 12.1-22.8% of maximal voluntary contraction for knee extension and flexion in the knee osteoarthritis group. The relative reliability was excellent for all four muscle groups, ranging from 0.96-0.97 on the affected and 0.96-0.98 on the non-affected sides the hip osteoarthritis group, and 0.92-0.99 and 0.96-0.98 in the knee osteoarthritis group. Conclusion: The absolute reliability of the hand-held dynamometer tended to be greatest for measurements of the affected joint, and relative reliability was excellent at all four testing sites, for both groups. The results of this study support the use of hand-held dynamometry for knee extension and knee flexion assessment in patients scheduled for knee replacement surgery and hip abduction and hip extension in patients scheduled for hip replacement surgery.