Relationship between active knee extension and active straight leg raise test measurements

This study was conducted to determine the relationship between two alternative tests for indicating hamstring musculotendinous length, active knee extension (AKE) and active straight leg raise (ASLR). Before alternatives to a commonly practiced clinical test such as AKE can be recommended for application, their convergent validity should be established. Twenty-three healthy subjects (mean age = 29.4 years) were tested. A 35-mm camera was used to record the position of the right side of the pelvis and lower limb during the performance of the ASLR test on the right. The camera set-up was also used to record the position of the right knee and pelvis during the performance of AKE with the right hip flexed to 90 degrees. For ASLR, the angle of the straight leg to the horizontal was measured. For AKE, the angle of knee extension was measured. The intraclass correlation coefficients for the AKE (.861) and ASLR (.953) tests were good and high, respectively. There was a significant relationship (r = -.718; r2 = .515; p < .001) between AKE and ASLR. The significant correlation between the measurements obtained using these two tests suggests that both are providing an indication of the same basic phenomenon, presumably hamstring musculotendinous length. For this reason, the AKE test may be a useful alternative to the straight leg raise test for providing an indication of hamstring muscle length.