ORIGINAl ARTIClE

The iliopsoas muscle

Agust Jorgensson and the lumbar spine

The influence of the iliopsoas muscle length on he iliopsoas is the only muscle rotation of the lumbar spine or, in postural and mobility characteristics()f the Tgroup in the body with direct cases of extreme shortening, to draw lumbar spine was investigated in 60 normal attachments to the spine, the the lumbar spine into the opposite male subjects. The passive physiologJcal and pelvis and the femur. Therefore it has movement directions, thus causing a accessory intervertebral movements were the potential to influence, and be scoliosis or a list of the lumbar spine assessed. Measurements which provided influenced by, movements at both the (Kennedy 1978, Michele 1963). estimations of the lumbar lordosis, lumbar spine and the hip joints. Similarly, components of extension and iliopsoas muscle length were The iliopsoas is a postural muscle and compression and of anterior shear also recorded. A difference was found in the has been observed to demonstrate a forces on the lumbar spine have been iliopsoas muscle length with respect to the striking tendency to shorten 0" anda postulated to accompany the basic mobility of the passive physiological and 1978 and 1983). The few studies which actions of the iliopsoas muscle accessory intervertebral movements at the L1- have investigated the length of the (Gracovetsky et aI1977, Nachemson L2 and T12-L 1 segments, and at the L2 and L1 iliopsoas have found that 1968, Troup 1975). These assumptions levels respectively. As the iliopsoas muscle approximately 20-35 per cent of are based on geometry, mathematical shortened, the intervertebral mobility increased. normal individuals show a 5 degrees or calculations and clinical impressions, Furthermore, the iliopsoas muscle length more extension deficit at the hip joint but have not been substantiated by showed a weak tendency toward a correlation attributable to the iliopsoas muscle research. Thus, although a shortening with the lordosis and the lordosis tended to (Barber et al1985, Hellsing etalI987). of the muscle group might be expected increase asthe muscle shortened. No correlation In the two studies listed, the muscle to enhance the accessory compression was found between the iliopsoas muscle length length was tested by a procedure and shear forces, these have not been and the range of lumbar extension. similar to the one recommended by demonstrated experimentally or [Jorgensson A: The iliopsoas muscle and the Janda (1983). clinically. However, many lumbar spine. Australian Journal of When shortened, iliopsoas has been physiotherapists use a regime of Physiotherapy 39: 125-132] described as increasing the lumbar iliopsoas muscle stretching in the lordosis O"anda 1983, Kendall and treatment of lumbar spine disorders in McGreary 1983, Kennedy 1973 and an effort to achieve optimal results. It 1978, Michele 1960 and 1963, Philips is suggested by some practitioners that 1975, Weintraube 1986). However, this may be important, especially in only two studies have investigated this cases of hypermobility of the lumbar relationship, and neither of these . spine, which may be attributed to Key words: Psoas muscles; demonstrated a significant relationship iliopsoas shortening. Lumbar vertebrae; Lordosis; between iliopsoas length and any In view of this knowledge, a study increase in lumbar lordosis (Barber et was devised to examine the nature of Movement al 1985, Toppenberg and Bullock such a potential relationship. 1986). Materials and methods Other authorities have also considered that a shortened iliopsoas A sample of convenience, consisting of muscle acts to limit the available range 60 male students ranging in age from of lumbar extension (Ingber 1986, 17 to 26 years (mean=19.5 years; A Jorgensson BSc(Physio), GradDipAdv Weintraube 1986). However, no S~D.=2.4years) was recruited. ManipTher is a practitioner in Reykjavik. Iceland. reported studies either support or Subjects were excluded if they had: and part-time tutor in the Physiotherapy Faculty dispute these claims. A shortening of of the Icelandic University. . a) any marked postural problems the muscle group has also been (for example a scoliosis or leg Correspondence: A Jorgensson, Kleppsveg 40, suggested to limit lateral flexion to the length discrepancy); 105 Reykjavik, Iceland. contralateral side and ipsilateral ORIGINAL ARTICLE

right rotation. This order minimised movement of the subject and made recording eaSIer. b) Passive accessory intervertebral movement tests (P AIVM) were conducted manually, commencing at the L5 vertebra and proceeding cephalad to the TIl vertebra. These tests were performed in the following order: central postero-anterior vertebral pressure, right unilateral postero-anterior vertebral pressure, left unilateral postero-anterior vertebral pressure. The passive intervertebral movement tests were graded on an ordinal scale ofone to five such that: l=hypomobile; Figure 1. 2=slightly hypomobile; Figure 3. Measurement of the incline at the S21evel. 3=normal; 4=slightly Measurement of the lumbar extension. hypermobile; 5=hypermobile. Gonnella et al (1982) used a From Page 125 seven point scale to study the therapists in evaluating the b) any previous major trauma or reliability in evaluating passive movements of the lumbar injury affecting their back or lower intervertebral movements, spine in five normal subjects showed intratherapist limbs; oJ.' adding ankylosed (0) and unstable (6) to the scale used reliability to be dependable c) ever experienced problems/pain in while intertherapist reliability their back or lower limbs which in the present study. The performance of five physical was not. Their conclusion was required medical treatment, that in studies where pa~ive limited activities of daily living or intervertebral movements are necessitated absence from school! B":angle recorded at used, the therapist as a source work. of variance should be kept Prior to their inclusion in the study, constant, eg all evaluations each subject was required to answer a x:;d.egree done by the one therapist. questionnaire to ascertain their of 2. To obtain an estimation of the suitability for inclusion. The subject lumbar lumbar lordosis, the standard also provided an indication of the .Iordosis Myrin goniometer, as modified by dominant or preferred leg (eg the one x'!"180~(90~ Grant (1984), was used to measure used for kicking a football). the inclines at the L1 and S2 levels The sequence of testing was x~fl~~~). (see Figure 1). From these values standardised to include: 9ak.B-. .. the angle of lordosis was calculated 1. a) Passive physiological adapting the method proposed by intervertebral movement tests ...... < •• : Cobb (1960) in his measurement (PPIVM) were conducted of the degree of curvature in manually, commencing at the subjects presenting with scoliosis. L5-S1 segment and Figure 2 illustrates the geometry proceeding cephalad to the _~~~~r. appropriate to this calculation. T11-TI2 segment. These Other studies have previously used tests were performed in the Figure 2. Cobb's (1960) method to calculate following order: Extension, Calculation of lumbar lordosis using the the lumbar lordosis (Barber et al right lateral fleJcion, left measured angles of inclination at l1 and 1985, Bullock et al 1987, rotation, left lateral flexion, S2. Toppenberg and Bullock 1986). ORIGINAL ARTICLE

figure 4. Figure 5. Performance of the lumbar extension. Test position for measurement of the iliopsoas muscle length.

3. For measurement of the lumbar in the muscle length test. For the asked to hold the flexed knee with extension, a modified lumbar measurement, each subject was both hands and maintain the spondylometer designed by Grant placed supine on the plinth with position. This positioning ensured (1984) was used to monitor the heels supported. Using a plastic that the lower limb to be tested movement between S2 and T12 ruler, a line was marked 5cm hung freely over the edge of the (see Figure 3). A posterior pelvic proximal to the superior edge of plinth, and the subject was asked tilt was performed prior to the each of the patellae. A strap was to relax the free hanging leg as initiation of the movel11ent but applied to the thigh just proximal much as possible (see Figure 5). then perniitted to be lost toward to these lines and a Myrin Following a 20-second period the end of the movement to ensure goniometer was attached to the which allowed for adequate low lumbar extension (see Figure strap by a Velcro fastening. The relaxation, a reading was taken 4). The reason for preceding the examiner then fully extended the from the Myrin goniometer. extension by a posterior pelvic tilt subject's knees to ensure that the This sequence of testing also served was to flatten the lumbar lordosis legs were lying straight on the to make the examiner blind to the and thus stretch the iliopsoas plinth and the goniometer was results of the objective tests of the muscle. That stretch was then calibrated to zero. Next, the lumbar lordosis, lumbar extension and expected to be accentuated by the subject slid down the plinth to iliopsoas muscle length while ensuing extension movement. stand at its edge. The subject was performing the more subjective tests of 4. Estimation of the iliopsoas muscle then asked to lie supine on the PPIVM and PAIVM. length performed first on the right plinth with the coccygeal region just over the end, so that the lower The examination was always carried side and then on the left. As it is out in the afternoon between one and limb to be tested would be free impossible to measure muscle six o'clock, to minimise the possible length in vivo as an absolute value, from any restraints offered by the plinth. While the examiner flexed effects of circadian variations in the length of the iliopsoas was flexibility (Gifford 1987). measured functionally using a the subject's non-tested lower limb method based on the one at the hip and knee, the lumbar Reliability procedures spine was palpated to ensure its recommended by Janda (1983). It To examine the intra- and inter­ flattening onto the plinth thus is admitted, however, that other examiner reliability, five subjects were eliminating the lumbar lordosis. intrinsic factors such as joint seen for each occasion. When the desired position had For the former, stiffness may playa role in limiting the subjects were seen by the examiner the maximum joint range achieved been attained, the subject was .... ORIGINAL ARTICLE

From page 121 '. : . '. -- -." ", on two occasions a week apart, at the · labla1> same time of the day and under the '.. ··.Res.of i~tra-aQdillter~exiURinerreliahilityprooedurastor Dleasuririg lhe . same environmental conditions. All · .1Or""sis~ llimbar extension ilmi~O"~as Ie:ng~. . .~. . skin markings were removed between sessions. For the latter, the examiner's ability in performing the measurements was compared against .·~~~t-~ an experienced manipulative physiotherapist. The examiner Lotdosis.· performed each test first, followed by 'Jntra.:.examiner o:r 1.66(9) (p:=n~I32)" the manipulative physiotherapist. Both (1.340 / 0-2°) used the same skin markings. The intra-examiner reliability was 88 per 0" 0.00(iJ) (p ~1.000} cent for PPIVMs and 93 per cent for (1.25° J 0_2°) P AIVMs. The inter-examiner ExtensiOn . '.' .. " .... .' reliability were 86 per cent for • In~~ex:uninerO,1° ··1.19(9)(p=O.250r "0.899 (p~O.oOO) . PPIVMs and 86 per cent for P AIVMs. .' (2.640 10:.,7°) From Table 1, it can be seen that . . there was a significant correlation for 1;1<> 2.4()(9) (P::O.04.() '. . 0:919 (p:;:O.OOQ) all the measurements obtained. No (1;45° Il-iO) significant difference was observed IlioPsoaS except for the inter-examiner Intra-examiner 0.2° 0.981 (p =0.000) measurements of extension. Upon 036(9)(p =0,162) examination of the reliability data, it (1.75° J 0-2°) came evident that the manipulative · Inter.:.examiner 0.5° 2.24(9) (p =n.052) 0.996 (P =0.000) therapist consistently obtained a value . (0.71°/0-2°) one to two degrees higher than the examiner. As the examiner always performed the initial measurement, this is likely to have occurred because of a slight mobilising effect from the previously performed movement. Results Passive intervertebral movements tests: The means for these tests are shown in Table 2. The scores for lateral flexion, lahlal. rotation and unilateral pressure on Passive intervertebral movement tests - the general distribution 0' mobility scores. each side were averaged because when hyper- or hypomobility was found on one side, the other tended to show the PPIVM . PAIVM Total same findings. Ext LF Rot Central Unilateral The lumbar lordosis, extension and Hypomobile . 4.1% 0,9% 1;5% 2.1% 0.7% 1.8% iliopsoas muscle length: The mean values obtained for these measurements are reported in Table 3. A t-test analysis showed no significant difference to exist between the ~~~.;i.••..••..=·., •...•...: • ..•.•.•~.. : .•..•..,.mQ•..••.•.•.• ·, .•• ·o.•.••.•• :•. ~.,·.! •..·.·.b.· .•1:.... bi1e.•. ·.·.n...... · i....e, •••.•.•••.••.•. ,: ..••.•••.•••.•,l ..~ .••...·o:.a.;.·.·.:.· ..29.:.:., .•.. o~.•.; .•. : •..•. ; ...•..•• ,,' .•,. ~i\ff~~U•..•..• ,.! ..•.••.•..110 •... ~.·..•7.3g.1 •..;.~ .. •••..·:·~fili \!~~'/ VA", ... ·,·.·,.·· ...... , .... '... <;)..•...••.•••• ·.<.'.0.. ·" •. ••..•.•.••..·: .. .•..•.... l ...•.••.•..) •.•.. .. .•. .: :: ...... :" ":. ; ...... : :.: .... :.. : :" ... :" :":".: :.".:: ~-:: : : .. ;2..... iliopsoas muscle length on the right ~'-!'1~~ ...... EOQ~()%

difference in muscle length could be it was sometimes only possible to attributed to leg dominance either on compare the normal group with either T~~r~3. the left side (t (57)=-0.80, P =0.427) or of the other two. I\lh~al'! value!! for the lumbar I,ordosis, the right side (t (57)=-0.87, P =0.3 89). A significant difference between .ionl~:ili°tit~mu~,~,.. . For this reason, leg dominance was not groups with respect to the iliopsoas further considered as a variable in any muscle length was demonstrated in the .: ...::.' of the subsequent statistical analyses upper lumbar spine and at the M~:;~ng~··';;,;; performed. . thoracolumbar junction: that is, as the (SO/range) The iliopsoas muscle length and the segmental mobility increased, the passive intervertebral movement tests: length of the iliopsoas decreased. This .. :~: .. ::.: .. :.: .. :\ <\/t~: ; ::\ :;,::::i";:.: ~;'::::;,;:.::: A one-way analysis of variance was significant difference was L6tdosiJ'/' 29.1<;\" used to investigate any differences demonstrated at the T12-Ll segment (8.$°/&°_509) between the groups formed by the with respect to the PPIVMs tests of •. {<:, \ passive intervertebral movement extension (F (1,57)=7.2460, p=0.0093), .~;, 25.6~, ratings with respect to the muscle lateral flexion right (F (1,57)= 7.3877, (7.09d2.5o-48:5~) length of the iliopsoas. p=0;0087) and left (F(I,57)=3.4477, ~SQaS!/';" -3 39°<' Because of the rarity of the p=0.0685), rotation right \\ • (61~j-190t,~&j' hypermobile and hypomobile ratings, (F (1,57)=8.0926, p=0.0062) and left it was necessary to collapse the rating (F (1,51)=6.9420, p=O. 0108). At the Ll-2 system to obtain groupings of subjects segment, this difference was likewise of sufficient size for the analysis. Three found with respect to the PPIVMs p=0.1637). This significant difference groups were formed, a normal group tests of extension (F (1,56)=6.2024, was similarly demonstrated at the L 1 (mobility score 3), an hypermobile p=0.0158), lateral flexion right level with respect to the PAIVMs tests group (mobility scores 4 and 5) and an (F (1,57)=4.4654, p=0.0390) and left of central pressures (F (1,57)=13.3478, hypomobile group (mobility scores 1 (F (1,57)=9.0576,p=0.0039) but not with p=0.0006), unilateral pressures right and 2). Even with these measures, the rotation right (F (1,58)=1.2375, (F (1,57):;:2.7687,p=0.1016) and left insufficient number of subjects meant P =0.2706) nor left (F (1,57)=1.9904,

Til-Ll'

.... '<:~' .... ·;i ..... '~'.·:;~.~en~:~~v~~~~~~;iight:~!~~") :. :... :~. :' ;/ '\~e. 50o'd~···'· ~7.5000~" ··········~5.9167~

~~~;~~e) . ".J3Y5231~i"'L~.196i~ (')lj.451& .. 3.94ci~' '\.LJ .87S(h: (Normalrn()bility) ~~~~!~ile) ,...... ·.····.···.···.··2.28$7<1·· ··.<·· ••. 3.0000? ".:LI-L:2·,· M~de l~~gm (a~~gedf6rthe right: and left side)' '., ...9rp 2 ... -5.5000° -7.1667° -9.0000° -5.5000° -6.1110°

:'< (H1:~hilej, -1.;b970 -2.58000 -2:3~24° -3.0196° -t~600o> \/ (NogJJ~1 mobility)

Ext=extension; LFRlLFL=lateral flexion right/left; RRlRL:;:rotation rightlleft. ORIGINAL ARTICLE

From page 129 (F (1,57)=8.0264, P =0,0064). At the L2 level, this difference was likewise found with respect to the PAIVMs tests of central pressures (F(I,57)=5.2987, p=0.0250), unilateral pressures right (F(I,56)=7.7227,p=0.0074) and left (F (1,56)=4.2080, p=0.0449). For the analysis with respect to the Ll-L2 segment and at the L2! level only ~o groups were includedm the analYSis. However, at the TI2-Ll segment and at the Lllevel, all three groups were used in the analysis. Therefore, it was possible to test if they were linearly related in the analysis of variance (polynomial=l; weighted linear tenn) thus making the results more significant (see Tables 4 and 5). When the non-significant findings were examined it was evident that the PPIVM test of extension demonstrated the same trend as the significant findings at all segments except at the Tll-T12 segment where no definite trend could be observed. The PAIVM test of central pressure likewise showed the same trend at the L4, L3 and T12 levels while no definite trend was found at the L5 and TIl levels. With respect to the other passive intervertebral movement tests, no consistent pattern could be examined, a predominance ofnonnal students aged 18-25 years. demonstrated. mobility scores was clearly established. The lumbar extension: Extension This is not surprising as the sample showed a mean value of25.6 degrees. The iliopsoas muscle length and the used in this study comprised healthy lumbar lordosis: The relationship Lane (1981) employed a similar young subjects. When a nonnal score method to that described iil this study between the iliopsoas muscle length was not obtained, a hypomobility score and the lumbar lordosis was examined and obtained a considerably lower was a much more common finding mean angle of 17 d~grees for 20 male using the Pearson product moment than hypermobility. Extension and correlation. It was apparent that a weak students aged 15-24. Taylor and central posteto-anterior vertebral Twomey (1980) and Twomey (1979) tendency toward a relationship existed pressure were the movements that such that when the muscle shortened likewise measured the sagittal range in demonstrated the highest number of the lordosis tended to increase 24 cadavers and 108 living male hyper- and hypomobility scores. A (r =0.4033, p =0.001). subjects respectively, aged 20-35. The general trend was seen for mean range for extension in the The iliopsoas muscle length and the hypermobility scores to be . cadavers was 13 degrees. The lumbar extension: No significant concentrated in the lower lumbar spme extension range for the living subjects relationship was found between the and at the thoracolumbar junction, was not specified but was said to be length of the iliopsoas and lumbar while the intennediate segments consistently lower than for the extension when their relationship was showed a higher frequency of cadavers and less than 60 per cent of examined using the Pearson product hypomobile scores. the flexion range. The total sagittal moment correlation (r =-0.101, The lumbar lordosis: The mean angle range was 42 degrees. The total p =0.221). of29.1 degrees compared favourably sagittal range for subjects aged 13-19 with a mean angle of 26.6 degrees was 45 degrees (Twomey and Taylor Discussion found by Barber et al (1985), using the 1987). The difference between the Passive intervertebral movement tests: same method to obtain an estimation values reported in the present study When the results from these tests were of the lumbar lordosis in 20 male and these other two is at least partly ORIGINAL ARTICLE

the result of one additional vertebral very high percentage ofnormal ratings, muscle may be more frequent in males. segment being included in the definite conclusions are hard to reach. The iliopsoas muscle and the lumbar measurement, namely the TI2-Ll Nevertheless it can be stated that if the extension: No significant relationship segment. Furthermore, with respect to iliopsoas muscle affects the was observed between the iliopsoas the studies by Taylor and Twomey intervertebral mobility, the results muscle and lumbar extension. Thus the (1980) and Twomey (1979) the reported would tend to suggest that results from this study do not support difference in age between subjects in shortening of the muscle would be the claims made by some authors these and in the present study might most likely to cause increased mobility (Ingber 1986, Weintraube 1986) that have played a role as the ranges of in the upper lumbar spine and at the shortening of the iliopsoas muscle acts spinal movement have been shown to thoracolumbar junction, especially in to limit lumbar extension. decline with age (Taylor and Twomey extension and anterior glide. 1980). How the extension was These findings thus support the Conclusion performed might also have been assumptions made in the literature that Within the limitations of this study, it important, as in the present study, the the actions of the iliopsoas muscle are can be concluded that the iliopsoas eJ(.tension was preceded by a posterior likely to be accompanied by anterior muscle group exerts an influence on pelvic tilt, whereas this was not the shear forces (Gracovetsky et al 1977, the lumbar spine, its posture and case in the other studies. Troup 1975) and may contribute to the intervertebral movements. If The iliopsoas muscle length: A value development of hypermobility. shortened, the muscle may possibly of minus 3 degrees was observed to The iliopsoas muscle and the lumbar contribute to some disfunction in the correspond approximately to a lordosis: The correlation between the lumbar spine. horizontal position of the thigh during iliopsoas muscle and the lumbar the testing procedure. The mean angle lordosis support the clinical findings References recorded in this study thus supports that a shortening of the muscle would Barber A, Dimopoulus A and Hogan A (1985): the normal position advocated by tend to exaggerate the lumbar lordosis Iliopsoas and rectus femoris-effect on lum,bar Janda (1983). Ganda 1983, Kendall and McGreary lordosis in standing. Unpublished thesis, Adelaide: South Australian Insti~te of Furthermore, a 5 degree or more 1983, Kennedy 1973 and 1978, Technology. extension deficit at the hip joint Michele 1960 and 1963, Philips 1975, Bullock JE, Jull GA and Bullock MI (1987): The attributable to the iliopsoas has been Weintraube 1986). The weak nature of relationship of low back pain to postural used as a criterion for marked the correlation is to be expected as changes during pregnancy. Australian Journal shortening ofthe iliopsoas muscle other factors intrinsic (Farfan 1973, ofPhysiotherapy 33: 10 .. 17. (Rellsing et aI1987). Using this Last 1984, White and Panjabi 1978, Cobb JR (1960): The problem of the primary criterion, a marked shortening of the Williams and Warwick 1980) as well as curve. Journal of]Jone and Joint Surgery 42A: muscle was observed in approximately extrinsic (Toppenbergand Bullock 1413 .. 1425. 33 per cent of the sample in the 1986) have been shown to exert an Gonnella C, Paris SV and Kutner M (1982): Reliability in evaluating passive intervertebral present study, which compares influential effect on the curve. motion. Physical Therapy 62: 436-444. favorably with a value of 35 percent When the results of this study are Farfan HF (1973): Mechanical disorders of the low obtained from 20 male students, aged compared with those of others who back. Philadelphia: Lea and Febiger. 18-25, in Barber et aI's (1985) study. have investigated the same Gifford LS (1987): Circadian variation in hum,an Hellsing et al (1987) reported a relationships, there are some flexibility and gripstrength.Australian Journal considerably lower value of 21.5 per differertcesas Barber et al (1985) found of Physiotherapy 33: 3 .. 9. tent obtained from a sample of 999 no significant correlation between the Gracovetsky S, Farfan HF and Lamy C (1977): A subjects (18 ..19 years of age) but the lordosis and the iliopsoas muscle mathematical model ofthe lumbar spine using gender of the subjects was not an optimized system to control muscles and length. However, their sample was ligaments. Orthopaedic ClinicsofNorthAmerica specified. The difference could be small (20 males, 20 females) and only a 8: 135-153. explained if a proportion of the sample few subjects presented with a Grant R (1984): Lumbar sagittal mobility in were females, since Barber et al 1985 shortened muscle (8 males, 3 females). professional dancers. Unpublished MAppSc noted a marked shortening in only 15 Toppenbergand Bullock (1986) thesis, South Australian Institute of percent of 20 female students aged 18~ likewise found no significant Technology (Cited by Grant, 1986). 25. Furthermore, Toppenberg and correlation between the lumbar curve Grant ER (1986): Lumbar sagittal mobility in Bullock (1990), in their study of 103 and the muscle length of the iliopsoas. hypermobile individuals . and professional adolescent females, found all angles for dancers. In Grieve GP (Ed.): Modern manual Their sample was quite different from therapy ofthe vertebral column. Edinburgh: the iliopsoas muscle length to be below the one used in this study, consisting of Churchill Livingstone, pp. 405-415. the horizontal. 103 adolescent females. This difference Hellsing AL, Nordgren B, Schele Rand Ahlborg B The iliopsoas muscle length and the might account for the different (1987): Predictability ofback pain around the passive intervertebral movement tests: relationship that was obtained, age of 20. Reproducability of examination As the passive intervertebral movement especially since the results of Barberet variables. Tenth International Congress, tests performed in this study showed a al (1985) suggest that shortening of the .. ORIGINAL ARTICLE

Last RJ (1984): Anatomy. Regional and applied. Troup JDG (1975): Mechanical factors in From Page 131 (7th ed.) Edinburgh: Churchill Livingstone. spondylolisthesis and spondylolysis. Clinical World Confederation for Physical Therapy, Michele AA (1960): The iliopsoas muscle. Its Orthopaedics and Related Research 117: 59-67. Sydney,pp.185-189. importance in disorders of the hip and spine. Twomey L (~979): The effects ofage on the ranges Ingber RS (1986): Iliopsoasmyofascial dysfunction: Clinical Symposia 12: 67-101. of mooons of the lumbar region. Australian A treatable cause of "failed" low back Michele AA (1963): Iliopsoas. Development of Journal ofPhysiotherapy 25: 257-263. syndrome. Archives of Physical Medicine and anomalies in man. Springfield, Illinois: Twomey LT and Taylor JR (1987): Lumbar Rehabilitation 67: 638. Charles C. Thomas. posture, movement, and mechanics. In Janda V (1978): Muscles, central nervous motor Nachemson A (1968): The possible importance of Twomey LT and Taylor JR (Eds): Physical regulation and back problems. In Korr JM Therapy of the low back. Edinburgh: (Ed.): The Neurobiologic Mechanisms in the psoas muscle for stabilization ofthe lumbar spine. 39: 47- Churchill Livingstone, pp. 51-84. Manipulative Therapy. New York: Plenum Acta Orthopaedica Scandinavica 57. Weinttaube A (1986): Soft tissue mobilization of Press, pp. 27-41. Philips KE (1975): Evaluation of the hip. the lumbar spine. In Grieve GP (Ed.): Modem Janda V (1983): Muscle function testing. London: Physical Therapy 55: 975-981. manual therapy of the vertebral column. Butterworths, pp. 162,225-226,230-233. Edinburgh: Churchill Livingstone, pp. 750- Taylor J and Twomey L (1980): Sagittal and Kendall FP and McGreary KE (I983): Muscle 755. horizontal plane movement of the human testing and function. (3rd ed.) Baltimore: lumbar vertebral column in cadavers and in White AA and Panjabi MM (1978): Clinical Williams and WIlkins, pp. 165,281,283. the living. Rheumatology and Rehabilitation 19: biomechanics of the spine. Philadelphia: JB Kennedy B (1973): Biomechanical problems 223-232. Lippincott Company, p.2. affecting the spine. Australian Journal of Toppenberg RM and Bullock Ml (1986): The Williams PL and Warwick R (1980): Gray's Physiotherapy 19: 9l-99. interrelation of spinal curve, pelvic tilt and Anatomy. (37th ed.) Edinburgh: Churchill Kennedy B (I978): Posture and pain. New Zealand muscle lengths in the adolescent female. Livingstone, pp. 329,489. Journal of Physiotherapy, May: 13-23. Australian Journal ofPhysiotherapy 32: 6-12. Lane ME (1981): The effect of age on the active Toppenberg R and Bullock M (1990): Normal and passive intervertebral movements of the lumbo-pelvic muscle lengths and their lumbar spine. Unpublished thesis, Brisbane: interrelationships in adolescent females. University of Queensland. Australian Journal of PhysWtherapy 36: 105- 109.