effects of ankle dorsiflexion on range and reliability of straight leg raising

Australian Journal of Physiotherapy 2000 Vol. 46 191

Introduction

The passive straight leg raise (SLR) procedure isroutinely used in the assessment of patients withlumbar pain. Often these symptoms are alsoassociated with symptoms that are in a sciaticdistribution. The significance of passive SLR is that ithas been shown to move the sciatic nerve adjacent tothe sciatic notch, as well as induce movement of, andincrease tension within, the lumbosacral spinalnerves, nerve roots and plexus, from which the sciaticnerve arises (Goddard and Reid 1965). Thesestructures can become acutely painful in the presenceof disc injury (Smyth and Wright 1958) and otherpathologies (Fisk 1975, Lerman and Drasnin 1975,Macnab 1971). Concomitant reflex musclecontraction in the hamstring group or gluteal muscles(Hall et al 1998) might restrict range of SLR asmeasured by range of hip flexion. Range of passiveSLR can therefore be an important clinical indicatorof nerve involvement in conditions of the lumbarspine (Alexander et al 1992, Macnab 1983).

Range of passive SLR does not, however, uniquelyreflect nerve involvement in lumbar spine conditions.It is also used to measure length of the hamstringmuscle group (Bohannon 1982, Hellsing 1988,Salminen et al 1992). Clinicians try to differentiatebetween short hamstring length and nerveinvolvement as the cause of pain during the procedure

by adding ankle dorsiflexion at the angle of hipflexion at which pain is produced (Breig and Troup1979, Troup 1981). This is thought to alter sciaticnerve length and tension without affecting hamstringlength. Physiotherapists utilise this knowledge of theeffect of dorsiflexion on the sciatic neuromeningealtree by adding it to other assessment and treatmentprocedures such as “slump”, which are designed tochallenge the neuromeningeal system (Maitland1985). Thus, not only can a clinician assess SLR todetermine whether hamstring or neural structures arecontributing to symptoms in patients with low backand/or leg symptoms, but the technique can also beused to more specifically target lumbar-sciaticneuromeningeal structures during treatment (Butler1991, Kornberg and Lew 1989). However, despite thewidespread use of dorsiflexion, little data areavailable that quantify the effect on passive SLR.

Gajdosik et al (1985) examined the effect ofdorsiflexion on passive SLR in asymptomaticsubjects by positioning the ankle in dorsiflexionbefore performing the procedure (SLR/DF) to endrange of hip flexion. End range was defined as thepoint at which the therapist felt the onset of firmresistance (R2) during the manoeuvre. Range of hipflexion during this procedure was then compared withrange of passive SLR without dorsiflexion to R2 anddorsiflexion was shown to reduce SLR by an averageof 10 degrees. Since ankle and knee braces were used

Boland and Adams: Effects of ankle dorsiflexion on range and reliability of straight leg raising

Effects of ankle dorsiflexion on range and reliability of straight leg raising

Robert A Boland and Roger D AdamsThe University of Sydney

The effect of dorsiflexion was investigated on range of passive straight leg raising (SLR) and on inter-raterreliability with 35 patients reporting unilateral lumbar pain with or without ipsilateral leg symptoms. Ranges ofSLR and SLR with dorsiflexion (SLR/DF) to onset of lumbar or leg symptoms (P1) were independentlymeasured using a gravity goniometer by pairs of different physiotherapists at two clinics. Dorsiflexionsignificantly reduced SLR range by a mean of 9 degrees across both samples. Similar high inter-raterreliability was found for SLR and SLR/DF in both pairs of physiotherapists. These data show that SLR andSLR/DF are reliable procedures when measured to P1 in the clinical environment and support previousfindings that dorsiflexion reduces range of SLR. [Boland RA and Adams RD (2000): Effects of ankledorsiflexion on range and reliability of straight leg raising. Australian Journal of Physiotherapy 46: 191-200]

Key words: Leg; Low Back Pain; Sciatic Nerve

Australian Journal of Physiotherapy 2000 Vol. 46192

to maintain limb position, and electromyography wasused to ensure that the hamstring group was relaxedduring testing, it is unclear whether clinicians couldexpect a similar magnitude of effect in a group ofsymptomatic patients. Conversely, it is also possiblethat the influence of pain during the SLR procedurecould magnify the dorsiflexion effect in asymptomatic group. Clinicians would benefit fromdata that quantifies how consistent these proceduresare in the clinical environment.

Another consideration, besides the effect ofdorsiflexion on range of SLR, is the effect that anklemovement could have on reliability of SLR. Anyinteraction between dorsiflexion and the conditioncausing the pain, or indeed the pain itself, mightaffect the repeatability of SLR/DF in a different wayfrom any effects on SLR. This would be reflected inreliability measures such as the intraclass correlationcoefficient (2,1) (Shrout and Fleiss 1979), which aresensitive to differences in bias between raters oroccasions. It is possible that superimposingdorsiflexion on SLR might reduce reliability if thetorque applied to achieve dorsiflexion varied betweenrepeat performances of the procedure, either within orbetween examiners, because this would affect theamount of pre-tension applied before hip flexion wascommenced. Not all of these issues can be answeredfrom the literature, since no studies were found thatmeasured the effect of dorsiflexion on SLR in apatient sample. Thus clinicians do not know what theeffects of ankle dorsiflexion are on repeatedmeasurements of SLR.

The purpose of this study was to investigate the effectof ankle position on range of hip flexion during SLRin a sample of patients with low back pain. It wouldalso evaluate the inter-rater reliability and errorassociated with repeat performances of SLR in twodifferent ankle positions with a patient group. Sinceclinicians use SLR/DF as a treatment technique,reliability and error data would reveal whether thetechnique itself could be used as a measurementprocedure in the presence of pain. It would be morevalid for clinicians to estimate treatment effects viachange in range of SLR/DF if this was the movementof interest instead of indirectly estimating effectsfrom change in range of SLR. Consequently,clinicians would then only need to consider whetherthe change in range of SLR/DF following treatmentwas of a magnitude greater than that associated withmeasurement error and the issue of how closely range

of SLR/DF correlated with SLR would not need to beestablished.

Methods

Subjects Patients from two physiotherapy clinicswere involved in the study. Group A consisted of 10male and 10 female volunteers aged between 20 and70 years with a mean (SD) of 50 (18) years, whoparticipated whilst attending for treatment at thephysiotherapy department of the Repatriation GeneralHospital at Concord, New South Wales. Group Bconsisted of 12 male and three female volunteersfrom the Royal Australian Navy aged between 21 and51 years with a mean (SD) of 33 (9) years, whoparticipated whilst attending for treatment at thephysiotherapy department at HMAS Kuttabul inSydney. Subjects were eligible to participate if theyhad unilateral lumbar spine pain, with or withoutipsilateral leg symptoms. The presence of lumbarsymptoms was considered justification for testing ofSLR during the physical examination. Exclusioncriteria were the presence of any of the following:inflammatory joint disease, cardiac failure,malignancy, recent spinal or lower limb fracture, hippathology and resting pain in the low back or leg priorto, or during, testing. Ethical approval had beengranted from the Ethics Committee of theRepatriation General Hospital, Concord and theAustralian Defence Medical Ethics Committee, forthe respective groups.

Examiners Four physiotherapists acted as examinersfor the study. One pair of physiotherapists collecteddata from Group A (Examiners 1 and 2) and adifferent pair collected data from Group B(Examiners 3 and 4). One examiner from Group Awas a physiotherapist with four years of graduateexperience and the other was a manipulativephysiotherapist with one year of postgraduateexperience. Both examiners from Group B weremanipulative physiotherapists, one with seven yearsand the other with four years of postgraduateexperience. Within each pair, one physiotherapist wasthe treating physiotherapist who took the patienthistory and continued treatment upon completion oftesting.

Experimental design Any patient who presented fortreatment of low back pain was provided withinformation about the study. After the treatingphysiotherapist had finished taking the patient’s



history and confirmed that all inclusion and exclusioncriteria had been met, the patient was invited toparticipate in the study. When written informedconsent had been gained, the subject was introducedto the other physiotherapist, who was not presentduring the history taking. Both physiotherapists thenleft the room and the subject undressed to bra andunderpants for females, and underpants for males,and put on a hospital gown. The treatingphysiotherapist then performed the physicalexamination to the point when testing of SLR wasusually performed. According to a random orderdetermined by lots, one physiotherapist measured theranges of SLR and SLR/DF. These were taken in theabsence of the other therapist and upon completion,the first physiotherapist left the room and the otherentered to repeat the measurements. Randomising theorder of examiners was undertaken to counter anyeffects from testing order on measurements becausean examiner who always tested second mightconsistently measure lower ranges to P1 if thresholdto pain lowered with repeated testing, or converselymeasure greater ranges if tissue compliance increasedor pain threshold increased.

The leg tested for each subject was always on thesame side as the subject’s back or leg pain and theorder of testing of the two different SLR procedureswas randomised for each examiner by drawing lots.Again, order was randomised to counter the effects ofpain or changes of tissue compliance during repeatedtesting. Once both examiners had taken and recordedthe total of four measurements, the treating

physiotherapist resumed the examination andtreatment of the subject. Each examiner within eachpair was blind to the results of the other duringtesting. For one subject, symptoms did not settleimmediately on return to the starting position afterone of the testing procedures, so testing was ceased.Data for that subject were not included in theanalyses.

Testing protocol Examiners were familiarised withthe testing protocol for each technique and were givena week to practise with the measuring instrumentwhich was a pendulum-type goniometer(a)

(pendulometer) before data collection wascommenced (Figure 1). The protocol for SLR wasaccording to the recommended standard (Breig andTroup 1979) that was already familiar to allexaminers but the SLR/DF was not, and theexaminers familiarised themselves with the techniqueduring the week of practice. The protocol for SLR/DFwas based on that used by Gajdosik et al (1985).

Starting position was with the subject supine on aplinth without a pillow for all measurements, withattempts made to align the trunk straight with nolateral flexion or rotation. The subject’s knees were


Figure 1. The pendulometer in position over the head of thefibula.

Table 1. Hip flexion angles and reliability data for straightleg raising (SLR) and straight leg raising with dorsiflexion(SLR/DF) for Group A.

SLR SLR/DF

Examiner 1 2 1 2

Mean * 56° 59.9° 46.2° 52.1°

Standard deviation 20.6° 18.1° 21.2° 19.4°

Mean across examiners 58° 49.2°

ICC (2,1) 0.86 0.89

95% Confidence interval for ICC 0.67-0.94 0.59-0.96

SEM 7.2° 6.7°

95% Confidence interval 14° 13°

ICC = Intraclass correlation coefficient

SEM = Standard error of measurement

* Significant differences for range of SLR/DF subtractedfrom SLR were found for Examiner 1 and for Examiner 2(F(1,19) = 86.76, padj< 0.001)


extended and range of SLR relative to the horizontalwas measured by a pendulometer that recorded hipflexion in 2 degree intervals. Thus the accuracy of theinstrument was ± 2 degrees. The pendulometer wasattached to a Velcro band placed around the lower legat the level of the fibular head to face laterally (Figure1) and was set to zero prior to testing. Examiners triedto maintain neutral hip alignment in all planes duringtesting.

Testing Procedure 1: passive SLR After asking thesubject to relax, the examiner placed one hand abovethe subject’s patella while supporting the lower legsuperior to the tendo Achilles with the other hand.The examiner then slowly elevated the leg to the pointwhere the subject reported the onset of any pain in theleg or back, (McCombe et al 1989) or stretch, pinsand needles or numbness in the leg or back. This pointwas defined as P1. Full knee extension wasmaintained during the manoeuvre to reduce errorsassociated with variation in knee angle (Callaghanand Williams 1991). The examiner noted the angle ofhip flexion at P1 from the pendulometer beforelowering the subject’s leg to the starting position andrecording the angle.

Testing Procedure 2: passive SLR/DF The subjectwas asked to relax, then the examiner placed one handabove the subject’s patella while the other handdorsiflexed the subject’s ankle to end of range(defined as R2) by applying pressure against theplantar aspect of the foot at the metatarsal heads. Theexaminer then slowly elevated the subject’s leg to P1while maintaining full knee extension. Range of hipflexion to P1 was noted from the pendulometer beforethe leg was lowered and the angle recorded.

Subjects were instructed to report the point of onset ofany lumbar or leg symptoms during testing. Thisdefinition of P1, therefore, did not specifically definethat symptoms produced replicated a subject’spresenting symptoms. This was justified on the basisthat it was unlikely that SLR or SLR/DF wouldreproduce every subject’s presenting lumbar or legsymptoms. Data as to whether symptoms producedduring testing matched subjects’ presentingsymptoms were not collected during either procedure.Additionally, the examiner measuring second did notinstruct subjects to report the point at which thecurrent procedure reproduced the same symptomsprovoked by the first examiner. This aimed to preventsubjects biasing their responses and to prevent


Table 2. Hip flexion angles and reliability data for straightleg raising (SLR) and straight leg raising with dorsiflexion(SLR/DF) for Group B.

SLR SLR/DF

Examiner 3 4 3 4

Mean * 53.2° 49.6° 42.1° 41.9°


Mean across examiners 51.4° 42.0°

ICC (2,1) 0.91 0.91

95% Confidence interval for ICC 0.72-0.97 0.75-0.97

SEM 4.8° 4.8°




*Significant differences for range of SLR/DF subtractedfrom SLR were found for Examiner 3 and for Examiner 4(F(1,14) = 72.03, padj< 0.001)

Table 3. Pooled hip flexion angles and reliability data forstraight leg raising (SLR) and straight leg raising withdorsiflexion (SLR/DF) from both groups.

SLR SLR/DF

Examiner 1 or 3 2 or 4 1 or 3 2 or 4

Mean 54.8° 55.5° 44.5° 47.7°


ICC (1,1) 0.88 0.89

95% Confidenceinterval for ICC 0.80-0.94 0.80-0.94

SEM 6.4° 6.1°






confusion from subjects trying to remember what wasfelt “two or three tests ago”.

Data analysis Data from Gajdosik et al (1985)showed a mean difference between passive SLR andSLR/DF ranges of 10 degrees with a standarddeviation of 5 degrees. It was determined from thesethat, for the current study, a sample size of 20 inGroup A would have 80 per cent power to detect aneffect size of 3 degrees. After data from Group A hadbeen collected, a sample size of 15 was chosen forGroup B, since this number would have 80 per centpower to find an effect size of 4 degrees (Welkowitzet al 1972). Data were analysed using Quattro Pro forWindows Version 5.0(b), and special-purpose softwarewritten to calculate the various forms of intraclasscorrelation coefficient (ICC) (Shrout and Fleiss1979) and repeated measures ANOVA (Winer 1971).

To determine inter-rater reliability of the SLR andSLR/DF procedures for each pair of examiners, ICCswere calculated from the 20 pairs of data for Group Aand the 15 pairs for Group B. The ICC (2,1) form

(Shrout and Fleiss 1979) was employed for theseanalyses. Repeated measures ANOVA wereperformed on data from Group A and then Group Bto evaluate effects due to i) ankle position duringtesting (dorsiflexed or not), ii) examiner (1 or 2) andiii) any interaction between these factors. As multipletests of significance were performed, observed pvalues were adjusted (p

adj) using the Bonferroni

method (Bland and Altman 1995) according to thenumber of comparisons made for each ANOVA. Thestandard error of the measurement (SEM) was alsocalculated, a statistic that can be expressed in theoriginal units of measurement and which representsthe standard deviation of the distribution of test-retesterrors (Domholdt 1993). As an approximation,doubling the SEM then adding and subtracting theresulting amount from any first measure gives a 95per cent confidence range (Domholdt 1993). This is avaluable calculation for clinicians, since a therapistwho performs a repeated measurement that variesfrom the first but lies within this range can attributethe difference to chance. Conversely, a secondmeasurement falling outside this range is more likelyto be due to systematic factors, such as treatment

Figure 2a. Agreement between examiners for thedorsiflexion effect for each subject within Group A. NB: Only17 data points are visible, since three are superimposed.The line of reference represents perfect agreementbetween examiners (y = x).

Figure 2b. Agreement between examiners for thedorsiflexion effect for each subject within Group B. NB: Only14 data points are visible, since one is superimposed. Theline of reference represents perfect agreement betweenexaminers (y = x).

SLR minus SLR/DF (degrees)Examiner 3

SLR minus SLR/DF (degrees)Examiner 1

SLR

min

us S

LR/D

F (

degr

ees)

Exa

min

er 2

SLR

min

us S

LR/D

F (

degr

ees)

Exa

min

er 4


effect or differences between examiners. Finally, toobtain better estimates of reliability and stability, datafor both groups were pooled. The ICC (1,1) formulawas calculated (Shrout and Fleiss 1979) since theexaminers who performed the measurements were nolonger the same throughout.

Results

The ICC (2,1) data from both groups indicated highreliability, not differing significantly between pairs ofexaminers or procedures (Tables 1 and 2). Whilevalues for ICC above 0.75 have been described asexcellent (Fleiss 1986) these data do not inform theclinician about error, nor express information in aform that can be readily compared with the expectedimprovement in range following a treatmentintervention. This information can be calculated fromthe SEM. For Group A, inter-rater test-retestdifferences of ≤ 14 degrees for measurements of SLRand ≤ 13 degrees for SLR/DF were consistent withsampling error or chance (Domholdt 1993). In GroupB, these respective data were 9 degrees for both SLRand SLR/DF.

Another way of describing agreement betweenexaminers for the two procedures is to compare theeffect of dorsiflexion for each subject betweentherapists. In Group A, the average differencebetween the two procedures (measurements ofSLR/DF subtracted from measurements of SLR) forExaminer 1 was 9.8 degrees compared with 7.8degrees for Examiner 2. In Group B, the averagedifference between the two procedures was 11.1degrees for Examiner 3 and 7.7 degrees for Examiner4. Figures 2a and 2b illustrate raw data for thedifference between the two procedures for eachsubject plotted against examiners. Figure 2a showsthat 95 per cent of the difference measurementsbetween examiners were within 10 degrees. Figure 2bshows that 86 per cent of difference measurementswere within 10 degrees. These data support the ICCand error data that imply consistency and stability ofmeasurements between examiners for the effect ofdorsiflexion on range of SLR.

The ANOVA for Group A indicated that the differencebetween the mean ranges of SLR and SLR/DF wassignificantly different (F(1,19)

= 86.76, padj

< 0.001) butthat neither the main effect of examiner (F

(1,19)= 6.36,

padj

= 0.06) nor the interaction between examiner andankle position during testing (F

(1,19)= 2.97, p

adj= 0.3)

were significant. Similarly, results for Pair B showeda significant effect of dorsiflexion during SLR (F

(1,14)= 72.03, p

adj < 0.001) but no significant effects

due to examiner (F(1,14)

= 3.08, padj

= 0.3) or examinerby ankle position interaction (F

(1,14)= 1.79 p

adj= 0.6).

Thus, the observed differences in range betweenprocedures were due to the effects of dorsiflexion onSLR and not from differences in the performance ofthe procedures between examiners or fromcumulative factors related to effects from examinersand dorsiflexion.

To obtain overall estimates of reliability and stability,data for both groups were pooled, yielding 35 repeatmeasurements of SLR and 35 repeat measurements ofSLR/DF. The ICC (1,1) formula was employed(Shrout and Fleiss 1979) since the four examinerswere no longer the same throughout testing of all 35subjects (Table 3). These data were consistent with theindividual group data showing comparable ICC (1,1)values and SEMs indicated that changes in range ofless than 13 degrees for either procedure after atreatment intervention are likely to be due to error if aconfidence level of 95 per cent is used (Table 3).


90degrees

Leg

vert

ical

Leg horizontal (leg on bed)

0degrees

Asymptomatics *

Symptomatics *

Figure 3. Effect of dorsiflexion on SLR in symptomaticand asymptomatic samples. Asymptomatic data is takenfrom Gajdosik et al 1985 and symptomatic data is pooledfrom Groups A and B.(* indicates significant difference between ranges).

To obtain a larger sample of measurements for eachprocedure, the pooled means of the repeatmeasurements for SLR and SLR/DF procedures werecompared. Figure 3 illustrates the effect ofdorsiflexion on SLR in the current group ofsymptomatic subjects by comparing these pooled dataof 70 paired comparisons with data from a sample ofasymptomatic subjects tested by Gajdosik et al(1985). Dorsiflexion reduced hip flexion range by 9degrees (p < 0.001) in the current sample ofsymptomatic subjects taken to P1 compared with aneffect size of 10 degrees in the sample ofasymptomatic subjects taken to R2 (Gajdosik et al1985).

Discussion

The aims of this study were to evaluate the effect ofankle position on range of SLR and to evaluate theinter-rater reliability of SLR performed with twodifferent ankle positions in a sample of patients, sincethese data did not exist. Pooled data from both groupsindicated that dorsiflexion reduced range of hipflexion during SLR by 9 degrees in a sample ofpatients with lumbar pain with or without legsymptoms, an amount almost identical to thatreported in previous research with subjects who wereasymptomatic (Gajdosik et al 1985). The ICC (2,1)values obtained from two pairs of physiotherapists forSLR/DF were as high as those for SLR and error datafor SEM were also comparable between tests. Thesedata indicate that the addition of dorsiflexion did notincrease the variability associated with SLR andsuggest that factors related to subjects (such as pain)and the SLR procedure (such as changes in handholds) have little effect on the difference in rangebetween the SLR and SLR/DF procedures.

Various analyses of consistency for SLR using fluid-filled and pendulum goniometers on patient groupshave been used in the literature and consequentlycomparison between data is compromised. Withoutthe presentation of reliability data in the units ofmeasurement, many data can be difficult to interpret.Previous percent agreement data showed that 71 percent (82 of 116) paired comparisons between threeraters were within a difference range of 10 degrees in55 patients with unilateral sciatica (Kosteljanetz et al1988). An ICC of 0.80 was reported between ratersmeasuring SLR in a group of patients with ankylosingspondylitis (Viitanen et al 1995) while ICCs of 0.96for left SLR and 0.94 for right SLR were found with

two pairs of raters investigating a group of patientswith low back pain (Waddell et al 1992). Inter-raterPearson’s correlations of 0.68 and 0.86 weredescribed in another sample of patients with low backpain (McCombe et al 1989) and a Pearson’scorrelation of 0.97 was quoted by another group usingan hydrogoniometer to measure SLR to estimatehamstring group tightness in 30 adolescents with andwithout low back pain (Salminen et al 1992). Highintra-rater data for SLR have also been reported instudies of patients with low back pain (Chow et al1994, Million et al 1982, Porter and Trailescu 1990)and asymptomatic subjects (Hsieh et al 1983, Rose1991).

While the procedure for SLR/DF in this studydiffered from the SLR procedure commonly used inclinical practice, inter-rater reliability for SLR/DFand SLR were similar in both groups. The usualprocedure for a clinician using SLR on a patient withlow back pain is to perform SLR to P1 or R2. If theaddition of dorsiflexion is indicated, the leg positionis held (Macnab 1983) or lowered a few degrees untilsymptoms have disappeared and dorsiflexion is addedin an attempt to reproduce low back or leg symptoms(Breig and Troup 1979, Haldeman et al 1988). In thisstudy, as is the case during certain manual assessmentand treatment techniques, dorsiflexion was taken toR2 before SLR was performed to P1 (Butler 1991).Despite these procedural differences, and despitecurrent testing protocols not requiring patients toreport that the same symptoms had been reproducedby each examiner, there was comparable reliabilityand error data between procedures. Thus, poor inter-therapist reliability of defining R2 that has beenpreviously reported (Matyas and Bach 1985) does notseem to have adversely affected the SLR/DFprocedure. Clinicians can therefore use SLR/DF andbe confident of its reliability and error in patientswith lumbar pain syndromes.

The inter-therapist reliability for both procedures washigh, even though an inter-examiner difference of 6degrees was found between SLR/DF procedures inGroup A (Table 1). In large part, high reliability wasobserved because the inter-rater differences wereproportionately small compared with the (up to) 90degree range of SLR expected across the population(Gajdosik et al 1992) and also observed in the currentsample. In fact, the small inter-rater variabilitycompared with the large within group variability inSLR ranges is a feature that gives robustness to theprocedures during repeated measures analyses and is



one basis for the observed high ICCs (Shrout andFleiss 1979).

The small but consistent inter-rater differences couldbe due to the automated nature of the testingsequence, that is, the role of habit with respect tospeed and torque of the leg raise within therapists. Itcould be argued that a clinician who is familiar withthe SLR procedure would probably be consistentbetween occasions of testing with respect toinstructions, starting position, speed and torqueapplied. Since instructions and starting position werestandardised in this study, the highly repeatable andconsistent differences in ranges of hip flexionbetween therapists could be indicators of consistentdifferences in applied speed and torque betweenexaminers during the procedures, although no datawere collected to verify this. The similarity betweenreliability data for both procedures, however,emphasises that the unfamiliar SLR/DF procedurewas easily learned by each examiner and wasprobably performed in a repeatable or habitualmanner (Magill 1989).

While intra-rater reliability data were not collected,current data provide clinicians with importantinformation about the effect of interventions designedto increase range of SLR or SLR/DF. By pooling datafrom both groups, the SEMs and 95 per centconfidence intervals were able to be determined forboth SLR procedures (Table 3). These data suggestthat a therapist who takes a repeat SLR measurementthat is within 13 degrees of a first reading taken byanother therapist is within the region of samplingerror. Similarly, a difference between therapists inSLR/DF range of less than 12 degrees could also beattributed to error. Since inter-rater reliability isgenerally lower than intra-rater data, these dataprovide clinicians with important information aboutthe effect of interventions designed to increase rangeof SLR or SLR/DF. Test-retest differences observedby a single therapist of greater than these ranges canbe considered conservative estimates of effects likelyto be due to treatment interventions or change in thecondition causing the symptoms. Thus, a therapistwho measures a post-treatment change in SLR withinthe error range should reserve judgment aboutwhether a treatment effect has occurred, since it hasbeen shown that repeated applications of SLR do notsignificantly increase the range of SLR (Chow et al1994).

While the 9 degrees decrease in SLR due to theaddition of dorsiflexion in this study of low back painpatients closely approximates the 10 degrees effectobserved in an asymptomatic sample (Gajdosik et al1985), the difference in procedures between studiescomplicates comparison of data. Examiners in thepresent study took SLR to P1 in both procedures,whereas the examiners in Gajdosik et al raised the legto R2 in both procedures. Nevertheless, a largerdifference than 1 degree between asymptomatic andsymptomatic samples might have been expectedbecause nerve involvement is more likely in a sampleof patients with lumbar pain compared with a sampleof asymptomatic subjects. In patients with lumbarpain, this would be expected to reduce the thresholdto pain provocation of movements such as ankledorsiflexion which affect lumbosacral and sciatictissues (Breig and Troup 1979, Goddard and Reid1965). The effect of this decrease in threshold wouldbe to reduce the difference between ranges of SLRand SLR/DF to P1 in a symptomatic group comparedwith an asymptomatic group. Comparatively higherthresholds might be expected if movements weretaken to R2 in an asymptomatic group resulting ingreater differences between ranges of SLR andSLR/DF. Further research would need to beundertaken to explore this hypothesis.

The observation that dorsiflexion to P1 reduced SLRby the same amount in both patient groups suggeststhat SLR/DF stresses different structures to SLR in aconsistent and reproducible manner. In fact, in onlytwo of 35 subjects tested did dorsiflexion not reducerange of SLR. In these two patients (each fromdifferent groups), only one physiotherapist from eachpairing found SLR range was greater than range ofSLR/DF. A logical conclusion is that ankledorsiflexion can be added prior to performing SLR tostress other tissues before the hamstring musclegroup. A large body of evidence suggests that thesetissues are continuous with the sciatic nerve (Briegand Marions 1963, Breig and Troup 1979, O’Connell1951, Smith et al 1993, Woodhall and Hayes 1950)and the results of this study are consistent with thatargument.

Conclusion

This study was conducted in the clinical environmenton a sample of patients in whom SLR would routinelybe assessed during the physical examination. Thefindings of high reliability and comparable error




ranges in such a patient group should, therefore, havegood external validity to the clinic if the sameprotocol is performed. Thus, data indicate thatSLR/DF can also be used as a measurementprocedure in addition to the SLR procedure and thatany difference in ranges between procedures is due tothe effect of dorsiflexion rather than subject orprocedural factors. A therapist who measures achange in range of more than 13 degrees for eitherSLR or SLR/DF can be confident that the change isnot due to error. Changes in range of less than thisamount could still be due to factors such as treatmenteffects but a therapist cannot be as confident aboutsuch a conclusion.

Authors Robert Boland, School of Physiotherapy,The University of Sydney, Post Office Box 170,Lidcombe, New South Wales 1825. E-mail:[email protected] (for correspondence).Roger Adams, School of Physiotherapy, TheUniversity of Sydney, Post Office Box 170,Lidcombe, New South Wales 1825.

Footnotes (a)Myrin Pendulometer, LIC RehabVardrum, Svetsarv 4, 17183 Solna, Sweden.(b)Borland International, 1800 Green Hills Road,Scotts Valley, Ca 95067-0001, USA.

Acknowledgements The authors acknowledge theassistance of the Physiotherapy Departments of theRepatriation General Hospital Concord, NSW, andHMAS Kuttabul, NSW, in recruiting subjects; theAustralian Defence Medical Ethics Committee; andJill Allen, Christine Davis, Con Traiforis and Chi YuiTsang, who acted as examiners or assisted with datacollection during this study. Data from Group A werepresented at the 9th Biennial Conference of theManipulative Physiotherapists Association ofAustralia in November 1995, and were published asan extended abstract in the Conference Proceedings.

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effects of ankle dorsiflexion on range and reliability of straight leg raising

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