THE RELIABILITY AND MINIMAL DETECTABLE CHANGE OF THE ELY AND ACTIVE KNEE EXTENSION TESTS

Background: Muscle length is a common component of the physical therapy examination, which may include the prone knee flexion (Ely) and active knee extension (AKE) tests. Clinicians using these tests should understand the clinimetric properties. Purpose: To investigate the reliability and minimal detectable change (MDC₉₅) of the Ely and AKE tests. Study Design: Reliability analysis. Methods: Seventy-one asymptomatic adults (mean age 24.6 +/-2.8 years) were recruited based on a con-venience sample. Two examiners each performed the Ely and AKE test one time each in an intrasession design for the interrater reliability component, with one examiner repeating the tests one time 48 hours later to determine the intra-rater reliability. Results were recorded based on one trial per test and utilized a pelvic strap for the Ely test and an adjustable bolster for the AKE test. A separate researcher recorded measurements and results were blinded from the examiners. Results: The Ely test had excellent intra-rater and inter-rater reliability with an intraclass correlation coefficient (ICC) (3,1) of 0.900 and ICC (2,1) of 0.914 respectively. The intra-rater and inter-rater reliability of the AKE test was good with ICC (3,1) of 0.882 and ICC (2,1) 0.886 respectively. The MDC₉₅ indicated that a change greater than or equal to 8° and 12° is required to exceed the threshold of error for the Ely and AKE test respectively. Conclusion: The Ely and AKE tests have good to excellent inter-rater and intra-rater reliability for measuring rectus femoris and hamstring muscle length when stabilization of the pelvis and hip is accounted for. The MDC should be considered as a threshold for true change in the asymptomatic adult population.