Reliability of Lower-Extremity Isokinetic Dynamometry Testing of the Ankle, Knee and Hip

Abstract

A comprehensive and clinically relevant lower-extremity muscle strength testing protocol in needed for use in elderly populations with mobility and balance disorders that is both efficient and reliable. Isokinetic dynamometry (ID) systems are commonly used to measure muscle strength in healthy and disabled individuals; 1 however, there are no data available on the test-retest reliability of ID torque measures for a comprehensive testing protocol. PURPOSE: To develop a comprehensive and efficient testing protocol for the ankle (dorsi/plantar), knee (flexion/extension), and hip (flexion/extension & ab/adduction), in healthy young adults, and assess the test-retest reliability of peak isokinetic torque of dominant and non-dominant legs. METHODS: Six healthy adults (mean age: 23±6 yrs, 4 female) were recruited for the study. Five trials of isokinetic testing were performed at 60°/s for each joint. Each trial consisted of a flexion/abduction trial, 15 sec rest, followed by an extension/adduction trial. After 15 sec rest another trial began. Each subject completed a second testing session after 1 week (same time of day). Test re-test reliability was assessed using the ICC (model 3). RESULTS: The testing protocol (which also included isometric and range of motion tests) took an average of 1.5 hours to complete. Isokinetic torque measurement for dominant and non-dominant sides were repeatable for hip extensors (ICC: dominant .88, non-dominant .90), hip adductors (.92, .90), knee extensors (.76, .90), ankle dorsiflexors (.88, .94) and plantarflexors (.91, .70). Limbs with excellent reliability only on the dominant side were hip flexors (.87, .31) and knee flexors (.76, .13). Hip abductor reliability was very poor for both sides (. 12, -.13). CONCLUSION: ID can be a reliable method for acquiring strength measures in young healthy adults. However, applications to older populations with musculoskeletal pathology, such as unilateral knee OA, will require additional protocol refinement, particularly for the hip abductors. Reliable measurements are required to better understand the role hip abductors play in preventing disease progression in people with medial knee OA.2 1. Salem et al. Med Sci Sports Exer 2000;32:1 679–84; 2. Chang et al. Arthritis Rheum 2005;52:3515–9. Funded by NSERC Discovery Grant # 50221566.