Comparison of Four Clinical Tests for Assessing Hamstring Muscle Length

Comparison of Four Clinical Tests for Assessing Hamstring Muscle Length Richard 1. Cajdosik, PhD, PT' Melonie A. Rieck, PTZ Debra K. Sullivan, PT3 Susan E. Wightman, PT4 Copyright 1993. All rights reserved. 0 bjective measurenients of hamstring muscle length are needed to quantify baseline limitations and to document the effectiveness of therapeutic interventions, both with patients i~nd with healthy people. Clinically, hamstring niuscle length is not measured directly but instead is represented indirectly by angular measurements of unilateral hip flexion with the knee extended [straight leg raise (SLR)] or unilateral knee flexion after knee extension with the hip flexed to 90. Although several tests are available, they liave not been compared, i111d their relationships liave not been reported. Knowledge of this information is important to help clinicians apply tlie tests appropriately and to accurately interpret the test results in light of tlie testing procedures. The passive SLR test probably is the most coninion clinical test used to represent lianistring length. The first author has administered passive SLR with the pelvis and the contralateral thigh secured in neutral positions with stabilization straps (SLR- SS). Althougli SLR may be influenced by structures other than the hamstrings (ie.. peripheral nerves and fascia) (6). hanistring length studies have indicated that this technique is probably a valid indirect test for hamstring length (5.4). Even Several indirect clinical tests for measuring hamstring muscle length are available, but the influence of their test procedures is not well documented. This study examined four of these tests to clarify the results relative to the testing procedures. The right limbs of 30 men were tested for: I) passive straight leg raise (SLR) with the pelvis and opposite thigh stabilized with straps (SLR-$5); 2) passive SIR with the low back flat and, if needed, the opposite thigh slightly flexed and supported on pillows (SLR-LBF); 3) active knee extension with the hip at 90" (AKE); and 4) passive knee extension with the hip at 90" (PKE). A dependent t-test showed no significant differences between the angles oi SLR-55 (61" + 6.7") and SIR-LBF (62" f 6.2'')). The SIR-SS and SIR-LBF angles for subjects needing pillows under the opposite thigh for the SIR-LBF test fn = 18) also were not significantly different. The knee flexion angles for the AKE (43" f 10.2") and the PKE (3 1" f 7.57 tests were significantly different (p < 0.001). Significant relationships (Pearson r) were found among the four tests (p < 0.05). The similar angles for SLR-SS and SIR-LBF and their significant relationship (r = 0.70, p < 0.001) indicated that their different testing procedures probably h;ld a minimal influence on test results. The difference between the AKE and PKE tests suggested that ihe AKE test and the PKE test may represent an "initial length" and a "maximal length," respectively. These results should help clinicians apply the tests appropriately and interpret the results accurately. Key Words: hamstring muscles, flexibility, straight leg raising ' Proiestor and Chairman, Phvsical Therapv Department, School oi Phc~rmacv and Allied Health Sciences. Universitv oi Ilontana, Missoul~,ZIT 598 I?- loi6 Staii Phvsical Ther<~pist, Oregon Rehabilitation Center, Sacred Heart General Hocpital. Eugene, OR ' Staii Phvsical Ther'lpist. Phvs~cal Therapv Department, WClthoe,Medical Center, Reno, I \ ' \ Staii Phvsical Ther~pist. Phvtical Therapv Department, St. Patrick Hospital.,Missoula,,111 This project wac supported In part bv grants from the Creative Projects Fund oi the Retearch Committee, (Montana Chapter oi the American Phvtical Therapv Association, and The Uni\wsitv oi,tlontana. though the specific details of the S1.R technique were not reported in the articles cited (5.4). tlie procedures of stabilization with straps were used (confirnied by RLG). Kendall (8) and Kendall and XlcCreary (9) advocate tlie SLK test with the pelvis tilted posteriorly approximately 10" and the low back flat on the table (SLR-LBF). Thev suggest that if this is not done. then SLK may appear less than SLR-LBF because hip flexion niuscle shortness would limit posterior rotation of the pelvis. They recommend screening for short hip flexion muscles using ;I hip flexion muscle tightness test (commonly referred to as the Thomas test) and supporting the contralateral limb in slight flexion if short hip flexors are present. Whether SLR-SS and SLR-LBF yield different test results is unknown and warrants clarification. \'olunie I8 Suniber 3 So\.cnilxr 19% JOSPT

.. Copyright 1993. All rights reserved. In addition to passive SLR tests, alternative methods of measuring hamstring length have been proposed. The active knee extension (AKE) test (6,7) and the passive knee extension (PKE) test (1 0. I 1) are both thought to be niore selective than SLR because the hip is stabilized at 90" of flexion and hamstring length is represented by the angle of knee flexion. As with the two SLR tests, the AKE and PKE tests have not been compared, and the relationship of the tests is unknown. The purposes of this study were to compare the hip flexion angles of SLR-SS with the hip flexion angles of SLR-LRF and to compare the knee flexion angles of AKE with the knee flexion angles of PKE. We expected to find that SLR-SS would be less than SLR-LBF for subjects with short hip flexion muscles. Even so, we espected the SLR tests to show a positive and significant relationship. We also hypotliesized that the knee extension tests would yield similar test results and show a positive and significant relationship. Because the SLR tests represent hamstring length bv the hip angle and the knee extension tests represent hamstring length by the knee angle, the angle of SLR tvould increase concomitant with it decrease in the knee angle. Consequentlv, we espected to find a negative but significant relationship between the SLR tests and the knee extension tests. METHOD Subjects Thirty, healthy men ranging in age from 18 to 40 years participated with informed consent. The means and standard deviations for their age, height, and mass were 22.8 f -5.3 years, 183.3 f 6.2 cm, and 78.1 +- 8.0 kg, respectively. The subjects were limited to men who were nonobese, had no genu recurv;tturn greater than.5", and had no history of orthopaedic or neurologic disor- ders. M'e screened all subjects to ensure that none had passive SLR greater than 90" because application of the knee extension tests is limited to subjects with SLR less than 90". No lower limit to the angle of SLR was set; this helped to ensure a wide range of scores. The study was approved by the University of Montana Institutional Review Board for the Use of Human Subjects in Research. Instrumentation An unpadded plynth was used for all tests. Cloth straps were used Clinically, hamstring muscle length is not measured directly but instead is represented indirectly by angular measurements of unilateral hip flexion with the knee extended. to stabilize the pelvis and the left thigh for the SLK-SS, the AKE, and the PKE tests. A gravity pendulum goniometer was secured to the right leg along a line between the fibular head and lateral nialleolus ;is described in ;I previous publication (6). The pendulum goniometer was used to mexure the angular displacement of the hip or knee, depending on the test. For the PKE and AliE tests, a wooden dowel on a franie apparatus was used to maintain the hip at 90 of flexion. l'his method wis essentially the same as described in a previous st utlv of the AKE test (6). Procedures All subjects were examined for short hip flexion muscles using a modified Thomas test (8). Kendall advocates this test prior to the SLR- LBF test as a method of determining potential difficulty for the subject to maintain the low back flat. In our study, the subject flexed his hips and knees until his low back was flat. He then held the left knee and extended the right hip until the limb stopped. The right knee was then passively extended by the examiner to remove the influence of the two-joint rectus femoris and tensor fasciae latae muscles. The inability of the right thigh to reach the horizontal plane was recorded as a positive test, primarily indicating shortness of the iliopsoas n~uscle. A positive modified Thomas test suggested the need to place one or niore pillows under the opposite thigh to position the low back flat during the SLR-LBF test (8). Immediately prior to testing, each subject performed five active toe touches to lessen the effects of muscle lengthening from repeated trials during data collection (1). The four tests were then administered in random sequence to the right lower extremity. The right ankle remained relaxed in plantarflexion for all tests because ankle dorsiflexion may limit the angle of SLR (5) and, presumably, also knee extension. A blind measurement technique was used: all tests were administered by the same examiner (DKS), and a second examiner read and recorded the measurements (SEW). Two test trials were performed for each of the four tests. Fifteen randomly selected subjects were retested after 30 minutes to assess the intratester test-retest reliability of all four tests. The procedures for each test are described below. SLR-SS Test The subject was positioned supine, and cloth straps were secured over the anterior superior iliac spines of the pelvis and across the midthigh of the left lower extremity. The examiner's left hand

KESEARCH STUDY Copyright 1993. All rights reserved. was placed over the distal anterior aspect of the right thigh to ensure that the knee remained in full extension. The examiner elevated the subject's right lower extremity with her right hand until firm resistance was felt and the subject confirmed that full SLR had been reached. SLR-LBF Test The subject was instructed to rotate his pelvis posteriorly and to flatten his low back against the plynth. The examiner checked this position at the start of the test by attempting to move a thin ruler placed under the low back. If the subject could not maintain a flattened back, an appropriate number of pillows was placed under the left thigh to assist with positioning. Care was taken not to overrotate the pelvis posteriorly. The examiner stabilized the left thigh with her right hand and then elevated the right lower extremity with her left hand until firm resistance to further hip flexion was felt and the subject stated that full SLR had been reached. The examiner closely monitored the knee to ensure that full knee extension was maintained during the test. AKE Test The subject was supine with one cloth strap placed across the anterior superior iliac spines and another across the midthigh of the left lower extremity. The subject actively maintained his right hip at 90" of flexion. The wooden dowel on the frame was in contact with the distal anterior surface of the right thigh to ensure that the right hip remained at 90" of flexion. The subject actively extended his right knee until myoclonus was observed. Then he flexed his knee slightly until the myoclonus stopped, thus defining the end point of motion (6). PKE Test The subject was supine with the cloth straps placed as with the AKE test. The examiner maintained the right hip at 90" of flexion with her left hand while moving the right knee through extension with her right hand placed over the distal posterior surface of the leg. The frame apparatus with the wooden dowel was used to maintain the hip at 90". The knee was extended passively until firm resistance to further motion was felt and the subject stated that maximum knee extension had been reached. Data Analysis The mean of the two test trials was calculated for all four tests, and descriptive statistics were then tabulated. Dependent t-tests were used to compare the angles of SLR-SS with the angles of SLR-LBF and to compare the angles of AKE with the angles of PKE. The Pearson product moment correlation coefficient was Some subjects reported that it was difficult to identify the point of myoclonus cessation for the active knee extension test. used to examine the relationships among the four tests. The results of the examination for short hip flexion muscles revealed that 14 subjects had a positive modified Thomas test. Twelve of these subjects needed one or more pillows under their left thigh, and two subjects did not need pillows. The positive modified Thomas test was considered a "false positive" test for the two subjects who did not need pillows to maintain the low back flat during the SLR-LBF test. The modified Thomas test was negative for the remaining 16 subjects in the study. Even so, six of these 16 subjects required pillows under the thigh to position their low back flat during the SLR-LBF test. The negative modified Thomas test was considered a "false negative" test for the six subjects who required pillows to maintain the low back flat during the SLR-LBF test. To help clarify the importance of using pillows under the left thigh to help flatten the back during the SLR-LBF test, a separate dependent t-test was used to compare the SLR- SS and the SLR-LBF for these subjects (N = 18). The examiner and all subjects provided their impressions about the ease or difficulty of all four tests. lntraclass correlation coefficients [ICCs, (2, I)] (2) were used to determine the intratester test-retest reliability of all four tests (N = 15). All data were analyzed with the Systat software statistical package (Systat, Inc., Evanston, IL) and a microcomputer. The level of significance was set at p r 0.05. RESULTS Figures 1 and 2 depict the two SLR test results (+SD) and the two knee extension test results (f SD), respectively (N = 30). Coniplete descriptive statistics for the results of the four tests are presented in Table 1. The angles of SLR-SS and SLR- LBF were not significantly different (p > 0.05). The angles of AKE and PKE were significantly different (P < 0.001). The ICCs for the test-retest measurements (N = 15) were FIGURE 1. Mean angles (f SD) of straight leg raise (SIR) with stabilization straps (SLR-SS) and SIR with the low back flat (SLR-LBF)(N = 30). m Volume 18 Number 3 November 1993 *JOSPT

Copyright 1993. All rights reserved. 1 SLR-SS SLR-LBF AKE PKE DlSCUSSlON P < 0.001 FIGURE 2. Mean angles (f SD) of knee flexion for active knee extension (AKE) and passive knee extension (PKE) (N = 30). TABLE 1. Descriptive statistics ior straight leg raise fslk1 angles with stabilization straps (SIR-SS), SIR angles with low back ilat (SLR-LBF), active knee extenwon angles (AKE), and passive knee extension angles fpke) (N = 30). SLR-SS = 0.83. SLR-LBF = 0.88, AKE = 0.86. and PKE = 0.90. A Pearson correlation matrix revealed significant relationships among all angular measurements (p < 0.05) (Table 2). The highest correlation was between SLR-SS and SLR-LBF (r = 0.70. p < 0.001). All passive tests were significantly related ( p < 0.001). as well as AKE and PKE (p < 0.00 1). The lowest correlations were between AKE and SLR-SS (r = 0.49) and between AKE and SLR-LBF (r = 0.37). The descriptive statistics for the SLR-SS and SLR-LBF for the 18 subjects requiring pillows under the left thigh to maintain their low back flat are presented in Table 3. The angles were not significantly different (p > 0.05). Miin? subjects reported that they had little difficulty with anv of the four tests. However, several subjects reported that it was awkward or dif- SLR-SS 1.00 SLR-LBF 0.70' 1.00 AKE -0.43t -0.37t 1.00 PKE -0.66' -0.65' 0.64' 1.00 p < 0 00 1 t p < 0.05. TABLE 2. Pearson correlation matrix for all four tests ior hamstring muscle length: I) straight leg raise (SLR) with stabilization straps (SLR-SS), 2) SLR with low back flat (SLR-LBF), 3) active knee extension (ME), and 4) passive knee extension (PKE) (N = 30). TABLE 3. Descriptive statrstlcs ior straight leg raise fslkj angles with stabilization straps (SLR-SS) and SLR angles with low back flat (SLR-LBF) ior subjects requiring pillows under the left thigh to maintain a flat low back for the SLR-LBF test (N = 18). ficult to maintain their low back flat for the SLR-LBF test. This was also noted bv the examiner. As a result, the examiner could not ensure that the subjects' positions remained unchanged during the test. The examiner noted that it was easy to see the end point of hip flexion because the knee began to flex. With the SLR-SS test, however, the end of hip flexion was determined by a change in resistance more than by a firm end feel. As described in the protocol, the subject's confirmation was important for determining the end point for all tests. Some subjects reported that it was difficult to identify the point of myoclonus cessation for the AKE test. Some subjects also had difficulty distinguishing between myoclonus of the hamstring muscles and shaking of the lower extremity. For the PKE test, the examiner described the end point of motion as firm and easy to identify. The finding that SLR-SS and S1.R-LBF were not significantlv different was not expected. Kendill and McCreary suggest that short hip flexion muscles of the limb opposite to the one being tested will limit SLR if the pelvis is not first tilted posteriorly with the low back flat (9). In other words, the hamstring muscles would appear abnormally shorter than they actually are. The results of our study did not support this claim. Even the subjects who required pillows under the left thigh to maintain the low back flat (N = 18) presented very similar hip flexion angular measurements for both SLR-SS and SLR-LBF. The authors acknowledge that the stabilization strap across the anterior superior iliac spines during SLR-SS probablv helped to secure the pelvis, and the low back may have been flat during the SLR-SS test. This could partially explain the similarity of the two test results. During SLR-SS, however, the left thigh was stabilized flat against the surface of the unpadded plvnth. In this position, short hip flexion muscles should limit the pelvis from rotating posteriorly. Based on our findings, positioning the left thigh in flexion to place the low back flat had a minimal influence on SLR when compared with SLR with stabilization straps. Subjects with shorter hip flexion muscles than the subjects we tested may be required to demonstrate the concern expressed bv Kenda11 (8) and Kendall and McCreary (9). Further research is needed to clarify this issue. The examiners noted that the results of the modified Thomas test did not alwavs indicate whether pillows should or should not be used during the SLR-LBF test. A positive modified Thomas test (N = 14) usually indicated that pillows were needed under the left thigh to maintain the low back flat; however, two subjects had "false positive" test re- JOSPT * Volume I8 * Number.i * November 1995 617

Copyright 1993. All rights reserved. sults because the positive modified Thomas test incorrectly predicted the need for pillows. On the other hand, a negative modified Thomas test (ic' = 16) did not always indicate that the subject could maintain the required position without pillows; six of these subjects presented "false negative" test results because they required pillows to slightly flex the left thigh. The authors acknowledge that the pelvis may have overrotated posteriorly during the modified Thomas test and that this may have contributed to the "false positive" test results. Indeed, identifying the beginning position of the Thomas test with the low back flat was sonietimes difficult. Based on the results of our study, the modified Thomas test may not always indicate the subject's ability or inability to maintain the low back flat. Clinicians should check the low back directly if the SLR-LBF test is used. The results demonstrated that the means of the AKE test and the PKE test were significantlv different (1 1.go difference, P < 0.00 1, Figure 2). This finding suggests that the two tests may represent different hamstring lengths. A possible explanation for this difference is that the AKE test may represent a measurement of an initial length (unstretched length). while the PKE test niay represent it measurement of the maximal length (fullv stretched) of the hamstring muscles. Gajdosik et al (4) and Gqjdosik (3) recently demonstrated that an initial length of the hamstring muscles can be measured by a point of initial resistance to passive stretch and that the muscles can be lengthened passively beyond this point to a maximal length corresponding to the maximal resistance to passive stretch. The AKE test requires the subject to extend the knee beyond a point of initial resistance that stimulates mvoclonus. The niyoclonus probably occurs within the range of extensibilitv of the muscles; that is, between the initial length and the maximal length. Slight flexion of the knee to the point of no myoclonus appears to return the niuscles to a point of initial resistance, or to a point where the muscles are not stretched. The PKE test, however. probably lengthens the muscles closer to a point of maximal length. Therefore, the difference between the two test results may represent the extensibilitv of the muscles, and this could be important clinical information. Greater posterior rotation of the pelvis during the PKE test than during the AKE test also could have contributed to the difference. Further research is indicated to examine these possibilities. The results also showed: I ) a significant positive correlation between the SLR-SS and SLR-LBF tests. 2) a significant positive correlation between the AKE and PKE tests, and 3) significant negative correlations between the SLR tests and the knee extension tests. These findings were consistent with our initial expectations because we believed that ;ill four tests were clinical indicators of hamstring muscle length. The findings that all of the passive tests showed the highest correlations and the AKE test showed the lowest correlations with the passive tests support the notion that the AKE test represents it hamstring length that differs from the passive tests. CONCLUSIONS The results indicated that the hip flexion angles for SLR-SS and SLR-LRF were very similar, even for the subjects who required pillows under the opposite thigh to position the low back flat. This finding casts doubt on the need to alwa\s flex the opposite thigh as suggested by Kendall (8). Clinicians and researchers alike should interpret the results of the tests for short hip flexion muscles cautiously and confirm a flat low back directlv if the SLR-LBF test is used. The AKE test had a significit11tly greater knee angle than the PKE test, indicating that the AKE test and the PKE test niay represent an initial length and a maximal length, respectively. Comparing the results of both tests may yield information about the extensibilitv of the muscles. The significant relationships among all four tests suggest that all of the tests probably represent similar, yet indirect measurements of hamstring length. JOSPT REFERENCES Atha I, Wheatley DW: The mobilising effects of repeated measurements on hip flexion. Br / Sports Med 10:22-25, 1976 Bartko 11: The intraclass correlation coefficient as a measure of reliability. Psycho1 Rep 19:3-11, 1966 Cajdosik RL: Passive compliance and length of clinically short hamstring muscles of healthy men. Clin Biomech 6:239-244, 1991 Cajdosik RL, Ciuliani CA, Bohannon RW: Passive compliance and length of the hamstring muscles of healthy men and women. Clin Biomech 5:23-29, 1990 Cajdosik RL, LeVeau BF, Bohannon RW: Effects of ankle dorsiflexion on active and passive unilateral straight leg raising. Phys Ther 65: 1478-1482, 1985 Cajdosik RL, Lusin CF: Hamstring muscle tightness: Reliability of an active knee-extension test. Phys Ther 63: 1085-1088, 1983 Cillette TM, Holland CI, Vincent Wl, Loy SF: Relationship of body core temperature and warm-up to knee range of motion. I Orthop Sports Phys Ther 13:126-131, 1991 Kendall FP: Trunk and Hip Muscles, Part I (Length Tests), Kendall Muscle Testing Video Library Program One, Baltimore: Williams R Wilkins, 1987 Kendall FP, McCreary EK: Muscle Testing and Function (3rd Ed), pp 148-153. Baltimore: Williams R Wilkins, 1983 Reimers I: Contracture of the hamstrings in spastic cerebral palsy: A study of three methods of operative correction. I Bone loint Surg 56B: 102-109, 1974 Worrell TW, Perrin DH, Cansneder BM, Cieck lh: Comparison of isokinetic strength and flexibility measures between hamstring injured and noninjured athletes. I Orthop Sports Phys Ther 13:ll8-125, 1991 Volurnc I8 Sumher.', Soven~her I993 JOSPT