Interexaminer reliability of the hip extension test for suspected impaired motor control of the lumbar spine

Objective: The hip extension test may be a clinical sign of impaired motor control in the lumbar spine, which may have a negative impact on spine stability. The purpose of this study is to evaluate the interexaminer reliability of the hip extension test for suspected dynamic instability of the lumbar spine in patients with chronic low back pain. Methods: Forty-two patients with chronic low back pain participated in this interexaminer reliability study. Chronic low back pain was defined as pain of greater than 7 weeks duration in the area between T12 and the buttocks, with or without leg pain. Two doctors of chiropractic simultaneously observed and independently assessed the left and right prone hip extension test on all 42 patients. Results for both examiners were given to an independent recorder. Each examiner was blinded to the results of the other examiner. Results: The mean age of subjects was 38 years (SD 12.35); 73.8% were female. Sixty-eight percent (SD 1.72) reported current back pain intensity greater than 5 on an 11-point numerical rating scale. The mean score for the Roland-Morris Low Back Pain and Disability questionnaire was 5.8 (SD 4.34). The K measure of agreement was 0.72 for the left leg and 0.76 for the right leg. This indicated a substantial strength of agreement between examiners for both left and right hip extension tests. For the 8 cases of disagreement, rater 1 generally rated the tests as positive, whereas rater 2 consistently rated the tests as negative. Conclusions: The hip extension test appears to have good reliability in detecting deviation of the lumbar spine from the midline. Validity with regard to the test's ability to distinguish patients with chronic low back pain from normal individuals and its relation to lumbar spine stability remains to be determined.