Relationship between Hip Extension Range of Motion and Postural Alignment

Relationship between Hip Extension Range of Motion and Postural Alignment JACKLYN G. HEINO, PT,' JOSEPH J. GODGES, PT, 0CS,2 CHARLES L. PhD, PT3 Journal of Orthopaedic & Sports Physical Therapy The purpose of this study was to examine the relationships between hip extension range of motion (ROM) and three determinants of postural alignment: standing pelvic tilt, standing lumbar lordosis, and abdominal muscle performance. The subjects were 25 healthy adults ranging in age from 21 to 49 years. The Pearson product-moment correlation of hip extension ROM with pelvic tilt was -0.04, with lumbar lordosis -0.09, and with abdominal muscle performance 0.09. These results indicate that these variables are not related. This study demonstrates that the hypothetical correlation among these clinical parameters needs to be reassessed. When evaluating the standing posture of their clients, clinicians often make assessments of pelvic symmetry and spinal curvatures in order to determine the appropriate therapy to improve postural alignment. For example, it is purported that an excessive anterior pelvic tilt will be associated with adaptively shortened hip flexor myofascia (5, 6) or limited hip capsule extensibility (7). Presumably, adaptively shortened hip flexor muscles and/or limited hip extension range of motion (ROM) provides an excessive anterior moment on the pelvis which results in 1) an accentuated lumbosacral angle producing an excessive lumbar lordosis, and 2) an abnormal lengthtension relationship between the lumbar erector spinae and abdominal musculature producing a "stretch-weakness" of the lower abdominals (5, 6). The relationship between pelvic tilt, lumbar lordosis and abdominal muscle performance was examined by Walker et al (1 1). They did not find any significant correlations between these three variables. The presumed relationship between hip extensibility and pelvic symmetry, however, has ' Physical Therapist. Ocean Park Orthopedic and Sports Therapy. 2664 29th Street. Santa Monica. CA 90405. 'Clmical Director. Kaiser Penanente Orthopaed~c Physical Therapy Residency Program. 6041 Cadillac Ave. Los Angeles. CA 90034. Associate Professor. Department of Physical Therapy. California State University-Long Beach. Long Beach. CA 90840. 0190-6011 P0/1 206-0243$02.00/0 TnE JOURNAL OF ORTHOPAED~C AND SPORTS PHYSICAL THERAPY Copyright 0 1990 by The Orthopaedii and Sports Physical Therapy Sections of the American Physical Therapy Association not been examined in a controlled clinical study. Therefore, the purpose of this study is to examine if a relationship exists between hip extension range of motion and three common clinical measures of postural alignment: pelvic tilt, lumbar lordosis, and abdominal muscle performance. The investigators of this study hypothesize that there will be a positive correlation between hip extension range of motion and abdominal muscle performance and a negative correlation between hip extension ROM and standing pelvic tilt and lumbar lordosis. METHODS Subjects The subjects were twentyfive healthy volunteers, 15 females and 10 males between the ages of 21 and 49 years, with a mean age of 25 years and a mean weight of 62.3 kg. No subjects were accepted with acute or chronic back pain, recent abdominal surgery, or hernia. These exclusions were made to avoid the distortion of data collection that could be the result of these factors. Instrumentation Pelvic tilt was measured with calipers (T. S. Stattler Co., Athol, MA) that were positioned on the anterior superior iliac spine (ASIS) and the posterior superior iliac spine (PSIS) of the subject. An inclinometer (Dasco Pro, Inc., Rockford, IL) was JOSPT 1293 December 1990 HIP EXTENSION ROM AND POSTURE 243

then placed on the calipers and the angle of the pelvic tilt from horizontal was read directly off the inclinometer. Lumbar lordosis was measured using a flexible curve (Staedtler Mars, Tokyo, Japan) molded against the subject's back to reproduce the lordotic curve. Hip extension was performed with the subject's knees maintained in 90 flexion using padded metal angles. These square angles were secured behind the knees using elastic wraps around the subject's thighs and calves (Figure 1). A standard goniometer was used to measure the angle of hip extension of the subject when he or she was placed in the modified Thomas Test position. Abdominal muscle performance was evaluated by using the double leg lowering test (DLLT) (6). This test requires the subjects to initiate and maintain an isometric contraction of their abdominal musculature while lowering their legs from a starting position of 90' hip flexion. The angle the femoral shaft makes with the table is recorded at the point the abdominals fail to maintain the isometric contraction holding the pelvis in a relative posterior tilt. This point was determined by placing an indicator (Franklin Sports Industries, Stoughton, MA) on the subject's ASlS and noting the movement made by the indicator. At the instant of movement, the goniometer was stopped. The speed of leg lowering was controlled by instructing the subject to keep time with a metronome as described by Walker et al (1 1). Procedures All subjects were informed of the nature of the study and signed a consent form. Both the study and the consent form were approved by the Human Subjects Committee at California State University-Long Beach. All measurements were taken twice to determine the reliability of the investigators. A one-minute rest was given to the subjects between each measure. One investigator (J. G. H.) took all hip extension ROM, lumbar lordosis, and DLLT measures while another investigator took all pelvic tilt measures. All data were collected in the Physical Therapy Pathophysiology Lab at California State University-Long Beach. The subjects were asked to remove their shoes and stand comfortably with their feet about shoulder width apart on a piece of paper taped to the floor. The outline of their feet was drawn to ensure that all measures were taken in the same position. The subject was asked to stand in the tracings for each subsequent measure taken standing. All bony landmarks were marked with tape which was removed after each measure. The order of measurements taken was randomly assigned for each subject with the abdominal performance measure taken following the other measures. These procedures were followed to ensure that no measure would be influenced by the taking of any other measurement and to ensure that the abdominal contractions from the DLLT test did not influence the static measures. Hip Extension ROM Measurement Measurements of the subject's right hip extension (ROM) were taken using a protocol modified from the procedure described by Godges et al (3). Subjects were positioned supine on a table and their knees were secured at 90" flexion using angles and elastic wraps to standardize the measurement position for all subjects. The subjects were then moved to the end of the table to ensure that their right knee was able to clear the table as the hip was extended during the ROM measurement. To further standardize the test position, one investigator held the left limb in midline with the hip flexed to 120 as determined by goniometric measure. The right limb was then raised passively until it was even with the contralateral limb and the subject was instructed to "relax this leg slowly down toward the ground." A second investigator used a goniometer aligned with the subject's right lateral femoral condyle and midpelvic line (as determined visually by the investigator). The measurement was taken as the limb ceased moving down in response to gravity, or ceased to remain in midline. Measurement of Pelvic Tilt Figure 1. Padded square angles secure subjects in a standard testing position for hip extension ROM measurement. The measurement of pelvic tilt (taken from the right side) was made with the subject in a relaxed, standing position, feet inside the tracings, as described by Walker et al (11). The investigator palpated and marked the subject's ASlS and PSIS and placed the calipers on the markings. An incli- 2 44 HElNO ET AL JOSPT 12:6 December 1990

nometer was placed on the calipers and the angle the pelvis made with the horizontal plane was read directly off the inclinometer (Figure 2). The angle read was marked positive if an anterior tilt was present, negative for posterior tilt. Journal of Orthopaedic & Sports Physical Therapy Measurement of Lumbar Lordosis Lumbar lordosis was measured using a flexible curve as described by Hart and Rose (4). The subject stood in the tracings while the examiner palpated and marked each PSIS. A mark was placed at the midline between these marks, presumably at the level of S2 with the bottom of the tape in line with the bottom of S2. The investigator then palpated the spinous processes up until reaching L1. Another mark was placed to indicate the superior border of L1. A flexible curve was then molded to the shape of the subject's spine between the two marks and the points corresponding to these markings were transferred to the flexible curve. The molded curve was then placed on a piece of paper and a tracing was made of the shape of the subject's lordotic curve. An index of lordosis, theta (fl), was obtained by using the formula described by Hart and Rose (4) 8 = 4 [arctan (2H/L)]. Abdominal Muscle Performance This study utilized the double leg lowering test as described by Kendall and McCreary (6) and modified by Walker et al (1 1). A further modification was made by the investigators of this study to create a more reliable end point for the measure. This modification was the application of an indicator to the subject's ASlS secured by tape (Figure 3). As the subject performed the DLLT, one investigator used a goniometer to measure the angle the legs made with the table at the point the indicator was seen to move. This was deter- Figure 2. Inclinometer and calipers positioned for determination of pelvic tilt angle. Figure 3. Indicator positioning for DLLT measurement. mined to be the point at which the subject was no longer able to maintain the pelvis in a relative posterior tilt with the low back pressed against the table. Presumably, this is the point the abdominals can no longer isometrically maintain the pelvic position against the force of gravity pulling on the lower legs (6). The investigator making the determination that the indicator moved was the same investigator taking the measure. This procedure was chosen to reduce the time lag between onset of movement and recording of measurement and increase the clinical applicability of the test. The subject was not made aware of the measurement point and continued lowering the legs until the hips were fully extended. No attempt was made to read the goniometer until the subject had completed the test. This was felt to ensure that the investigator did not attempt to duplicate the previous measure taken. Reliability Following each measurement, the examiner removed all markings. The subject was given a oneminute rest after which a second measurement was taken to determine the intratester reliability. Data Analysis An intraclass correlation (ICC) was made on all measurements to determine the reliability of the measurement procedures (8, 10). To assess the relationships of the measurements to each other, a Pearson product-moment correlation was calculated. RESULTS The means and standard deviations of the measurements are listed in Table 1. The ICC values obtained for intrarater reliability of the measurements of hip extension ROM, pelvic tilt, lumbar JOSPT 12:6 December 1990 HIP EXTENSION R( IM AND POSTURE 245

TABLE 1 Physical characteristics of subjects Hip extension ROM 171.OO 7.2 Pelvic tilt 10.OO. 3 Lumbar lordosis (8) 38.5' 11.5 Abdominal muscle perform- 44.0 21 ance (DLLT) TABLE 2 Pearson product-moment correlations Hip Extension PeMc Tilt Lumbar Lordosis DLLT ROM Hip extension 1.OO ROM Pelvic tilt -0.04 1.00 Lumbar lordosis -0.09 0.01 1.00 DLLT 0.09 0.30 0.27 1.00 lordosis, and DLLT were 0.91, 0.83, 0.89, and 0.94, respectively. The Pearson product-moment correlation of hip extension ROM with pelvic tilt was -0.04; with lumbar lordosis, -0.09; and with abdominal muscle performance (DLLT), 0.09. The Pearson product-moment correlations between all measures are listed in Table 2. DISCUSSION A high degree of intratester reliability for testretest measurements was found for all four of the clinical determinants of postural alignment examined in this study. The intratester reliability for the measurement of pelvic tilt using calipers and an inclinometer is in agreement with the findings of Walker et al (11) who reported an intratester reliability measure of 0.84. While some authors have described a method of utilizing a trigonometric formula for determining pelvic tilt (2, 9), investigators in this study believe the method utilized here is more adaptable to the clinical situation. Furthermore, since the landmarks used are the ASlS and PSIS, this method theoretically reflects the actual pelvic tilt angle (1 1). The high degree of intratester reliability for the measurement of lumbar lordosis found in this study is also consistent with other investigations. Hart and Rose (4) reported an ICC of 0.97 for intratester reliability utilizing the same flexible curve measurement used by the investigators of this study. Walker et al (1 I), using the area between L3 and S2 (instead of L1 and S2 as described by Hart and Rose [4]), reported an intratester reliability of 0.90. Furthermore, the flexible curve method using the area between L1 and S2 was also determined to have validity (r = 0.87, N = 8) when compared with roentgenographs (4). The measurement of abdominal muscle performance using the indicator on the ASlS with the DLLT test also demonstrated a high degree of reliability. Walker et al (11) utilized the DLLT with the point of pelvic movement determined by palpation of the low back with a reliability of 0.71. The authors believe that the improvement in this study in reliability over that reported by Walker et al is due to the new method introduced to determine the end point of the test. However, the inability of some subjects to achieve a standard starting position for this measurement due to variable hip extensor muscle flexibility may have contributed to the test results. This may have prohibited the reliability from being even higher. The goniometric measurement for hip extension ROM following the procedure first described by Godges et al (3) showed a high degree of reliability. This procedure utilizes the modified Thomas Test position with the knees fixed in 90 flexion to standardize the measurement position for all subjects (3). In a recent study this measurement procedure was found to have reliability measures ranging from 0.88-0.98 for retest measures by one investigator with a one-minute rest interval (1). Even though a high degree of intratester reliability for test-retest measurements was found for all four of the clinical determinants of postural alignment examined in this study, they were not found to be interrelated. While the correlation between hip extension ROM and abdominal muscle performance was positive as hypothesized, and the correlations between hip extension ROM and both pelvic tilt and lumbar lordosis were negative as hypothesized, none of the correlatiocs were significantly different from zero (p > 0.05). Thus, the data in this study does not indicate that the theoretical relationships between hip extension ROM and these clinical measures of postural alignment exist in a normal, asymptomatic population. The lack of significant correlation between these determinants of postural symmetry is relevant to clinicians in interpreting the results of their physical examinations and designing treatment programs for their clients. Specifically, results of this study demonstrate that clinicians should not design treatment plans for stretching supposedly shortened hip flexor myofascia or weakened abdominal musculature based on visual inspection of postural malalignments. The results of specific examination procedures testing joint mobility as well as muscle length, strength, and coordination are required to design and implement the appropriate therapeutic exercises. One reason for the lack of significant statistical correlation among the results may be due to the low range of variability present in these clinical measures (8). Another reason may be that a more complex relationship exists among these parameters of postural alignment than has been studied ET AL JOSPT 12:6 December 1990

to date. Perhaps a research design that compares the clinical parameters of two distinct groups may assist in answering these questions. For example, comparing the measures of pelvic tilt, lumbar lordosis, and abdominal muscle performance in individuals with marked limitation of hip extensibility to the same postural measures of individuals with excessive hip extensibility may provide greater measurement variability, possibly demonstrating stronger correlations. Another suggestion for future research would be to measure the changes in postural determinants before and after an intervention program designed to 1) elongate adaptively shortened hip myofascia and periarticular structures, 2) improve abdominal muscle performance, and/or 3) train individuals in efficient standing posture or gait mechanics. CONCLUSION No correlation was found to exist between hip extension ROM, standing pelvic tilt, standing lumbar lordosis, and the double leg-lowering abdominal muscle performance test. Further investigation is recommended to determine which factors do contribute to postural alignment and to deter- mine if these factors can be altered with therapeutic intervention. 0 The authors would like to ackassistance with data cdlectii. REFERENCES Lisa J. Landers for her 1. Engelke KA. Godges JJ: LhpuMished data. Pepperdine Uhrsily. Malibu. CA 2. Gajdosik R. Simpson R. Smith R. CkmTgny RL: Pdvic tilt: intratester rel~abil~ty of measuring the standing positii and range of motion. Phys Ther 65:169-174.1985 3. Godges JJ. MacRae M. Longdon C. Tinberg C. MacRae P: The effects of stretching procedures on hip range of motion and gait economy. J Orthop Sports Phys Ther 10:350-357.1989 4. Hart DL. Rose SJ: Rdiabil~ty of a noninvasive method for measuring the lumbar curve. J Orthop Sports Phys Ther 8:180-184.1986 5. Jull GA. Janda V: Muscles and motor control in low back pain: assessment and management. In: Tworney LT. Taylor JR. Physical Therapy of the Low Back. pp 253-278. New York: Churchill L~vingstone. 1987 6. Kendall FP. McCreary EK: Muscles, Testing and Function, 3rd Ed. pp 214-219. Baltimore: Williams 8 Wilkins. 1983 7. Kottke FJ. Pauley DL. Ptak RA: The ratlonab for prolonged stretching for mectlon of shcftenlng of connective tissue. Arch Phys Med Rehabl47:345-352.1966 8. Lahey MA. Downey RG. Saal FE: lnhgdass comlatifms: There's more there than meets the eye. Psych Bull 93586-595, 1983 9. Sanders G. Stavrakas P: A technique for measuring pelvic tilt: suggestions from the fid. Phys Ther 61 :49-50.1981 10. Shrout PE. Flelss JI: Intraclass correlations: uses in assessing rater rehabllity. Psych Bull 86:420-428. 1979 11. Walker ML. Rothstein JM. Finucane SD, Lamb RL: Relatiiships between lumbar lordosis, pelvic tilt, and abdominal muscle performance. Phys Ther 67:512-516.1987 JOSPT 12:6 December 1990 HIP EXTENSION ROM AND POSTURE