Screening for psychological factors in patients with low back problems: Waddell's nonorganic signs.

Scalzitti DA. Screening for psychological factors in patients with low back problems: Waddell's nonorganic signs. Phys Ther. 1997;77:306-312.]

Key Words: Assessment, Low back problems, Nonorganic signs, Psychosocial.

Waddell et al[8] described a group of signs that indicate the presence of nonorganic problems for patients with LBP. Waddell has also referred to these signs as "behavioral signs" or "inappropriate signs."[2,9] Testing for these signs is performed as part of the physical examination and takes less than 1 minute.[8] Nonorganic signs have been used to describe different characteristics of patients with LBP. The purpose of this update is to describe the use of Waddell's nonorganic signs as a screening tool for psychological factors in patients with LBP. Additionally, the relationship between the nonorganic signs and physical impairments, disability, and treatment outcomes will be discussed.

Waddell's Nonorganic Signs

In the early 1900s, nonorganic signs were frequently used to detect malingering in patients with LBP.[10,11] As medical and psychological knowledge progressed, it became clear that the diagnosis of malingering may have been based on overly simplistic assumptions, and the use of these nonorganic signs fell out of favor. The modern use of nonorganic signs for patients with low back problems increased greatly after 1980, when Waddell et al[8] grouped eight signs into five types. These five types, or categories of signs, are tenderness, simulation, distraction, regional disturbances, and overreaction (Table). Waddell and colleagues investigated 16 other signs, including grip strength, lumbar sensory changes, and pretibial tenderness, but did not include them in their final battery because of poor intertester and intratester reliability, overlap with other signs, and difficulty for the examiner to learn.

Table.
Waddell's Nonorganic Signs(a)

Type of
Nonorganic Sign         Nonorganic Sign

Tenderness

                        Superficial

                        Nonanatomic

Simulation tests

                        Axial loading

                        Rotation

Distraction tests

                        Straight leg raising

Regional disturbances

                        Weakness

                        Sensory

Overreaction

Type of
Nonorganic Sign         Description

Tenderness              Tenderness not related to a particular
                        skeletal or neuromuscular structure; may be
                        either superficial or nonanatomic.

                        The skin in the lumbar region is tender to
                        light pinch over a wide area not associated
                        with the distribution of a posterior
primary
                        ramus.

                        Deep tenderness, which is not localized to
                        one structure, is felt over a wide area and
                        often extends to the thoracic spine,
sacrum,
                        or pelvis.

Simulation tests        These tests give the patient the impression
                        that a particular examination is being
                        carried out when in fact it is not.

                        Low back pain is reported when the examiner
                        presses down on the top of the patient's
                        head; neck pain is common and should not be
                        considered indicative of a nonorganic sign.

                        Back pain is reported when the shoulders
and
                        pelvis are passively rotated in the same
                        plane as the patient stands relaxed with
the
                        feet together, in the presence of root
                        irritation, leg pain may be produced and
                        should not be considered indicative of a
                        nonorganic sign.

Distraction tests       A positive physical finding is demonstrated
                        in the routine manner, and this finding is
                        then checked while the patient's attention
                        is distracted, a nonorganic component may
be
                        present if the finding disappears when the
                        patient is distracted.

                        The examiner lifts the patient's foot as
                        when testing the plantar reflex in the
                        sitting position; a nonorganic component
                        may be present if the leg is lifted higher
                        than when tested in the supine position.

Regional disturbances   Dysfunction leg, sensory, motor) involving
                        a widespread region of body parts in a
                        manner that cannot be explained based on
                        anatomy; care must be taken to distinguish
                        from multiple nerve root involvement.

                        Demonstrated on testing by a partial
                        cogwheel "giving way" of many muscle groups
                        that cannot be explained on a localized
                        neuralgic basis.

                        Include diminished sensation to light
touch,
                        pinprick or other neurologic tests fitting
a
                        "stocking" rather than a dermatomal
pattern.

Overreaction            May take the farm of disproportionate
                        verbalization, facial expression, muscle
                        tension and tremor, collapsing, or
sweating;
                        judgments should be made with caution,
                        minimizing the examiner's awn emotional
                        reaction.

(a) Adapted from Waddell G, McCulloch JA, Kummel E, Venner RM. Nonorganic physical signs in low-back pain. Spine 1980;5117-125.

According to Waddell et al,[8] a nonorganic sign (an indication of a nonorganic contribution to a patient's low back problem) observed during the physical examination is scored as positive. If a sign is positive, then that type of nonorganic sign is present. One nonorganic sign in isolation may be present with some organic conditions and should therefore be discounted. A sensory regional disturbance, for example, may be present in persons with spinal stenosis with multiple nerve root involvement.

Waddell et al[8] found that the presence of three or more types of nonorganic signs correlated with the results of psychological tests indicating problems. According to Waddell et al, the presence of a single sign is not associated with an indication of psychological problems. The presence of three or more types of nonorganic signs has been the most consistently used criterion for the finding of a positive Waddell's nonorganic signs test, although other methods have been proposed.[12,13] Unless otherwise specified in this update, therefore, a positive test for nonorganic signs refers to finding the presence of three or more types of nonorganic signs. A negative nonorganic signs test is the finding of only one or two types of signs, although a patient may have more than three nonorganic signs because of multiple signs within a specific type.

Reliability

Agreement was high (86%) for two examiners in detecting the presence of nonorganic signs in a group of 50 patients with chronic LBP.[8] Agreement between examinations in the same patients was 85%. (The mean length of time between examinations was 23 days.) McCombe et al[14] reported poor intertester reliability between two orthopedic surgeons and between a surgeon and a physical therapist in detecting individual nonorganic signs. Confidence intervals of Kappa coefficients included zero for the nonorganic signs of tenderness and regional disturbances, suggesting that agreement was not better than chance. McCombe et al, however, did not examine the reliability of the examiners in determining the presence of three or more nonorganic signs. This finding should caution clinicians regarding the use of positive nonorganic signs in isolation.

The nonorganic sign of overreaction requires the clinician to make judgments based on observations of the patient's behavior. The other signs are from tests conducted during routine examinations. The presence of overreaction, therefore, may be more difficult to identify than other nonorganic signs. Several methods and instruments can be used to quantify observation of a patient's behavior during the physical examination.[15]

Keefe and Block[16] described a method for observing overt pain behaviors to provide a means of identifying the presence of guarding, bracing, rubbing, grimacing, and sighing during a physical examination. Waddell and Richardson[9] obtained a Pearson product-moment correlation coefficient of .65 when examining the relationship between the nonorganic signs test and overt pain behaviors in 120 patients who had LBP for at least 3 months. Measurements obtained with the UAB Pain Behavior Rating Scale, which is one instrument for measuring pain behavior, were also highly correlated (r = .73) with the results of the nonorganic signs test in 103 patients with LBP.[17]

Nonorgonic Signs and Psychological Findings

In their original study of nonorganic signs, Waddell et al[8] reported a correlation between the presence of nonorganic signs and scores on the hypochondriasis, depression, and hysteria scales of the Minnesota Multiphasic Personality Inventory. These scales of the Minnesota Multiphasic Personality Inventory traditionally represent a measure of psychological distress in patients with LBP. In addition, correlations have been found between the presence of nonorganic signs and other psychological instruments, including the disease affirmation and hypochondrial disturbance scales of the Illness Behavior Questionnaire (IBQ),[18] the Distress and Risk Assessment Method (DRAM),[19] and pain drawings.[8,20] Waddell et al[8] caution, however, that nonorganic signs should not be overinterpreted and used as substitutes for comprehensive psychological assessment. Instead, they should be used as part of an examination to identify patients who require more detailed testing.

The sensitivity and the specificity of eight psychometric instruments, including Waddell's nonorganic signs test,(*) for detecting psychological disturbances in patients with LBP were determined in a group of 264 persons.[12] Results from each instrument were compared with a "gold standard" of psychological disturbance, which was defined as a positive response to three or more of the eight psychometric tests. Specificity of the nonorganic signs for correctly identifying patients who were nonpsychologically disturbed was 86% in men and 84% in women. Sensitivity of the nonorganic signs for correctly identifying patients who were psychologically disturbed was 44% in men and 48% in women. This study was limited, however, by the lack of a universal "gold standard" of psychological disturbances with which to compare the different instruments. In the study, measurements with each instrument were compared with a compilation of measurements obtained with the other instruments. Correlations among the eight instruments may not have been found if the instruments were measuring different aspects of psychological disturbances.

Nonorgonic Signs and Demographics

Age, gender, occupation, or compensation status do not appear to influence the results of the nonorganic signs test.[8] Hayes et al,[21] however, found nonorganic signs more frequently in patients with LBP who were anticipating or receiving financial compensation as compared with those who were not anticipating or receiving compensation. In this study, however, other factors differed between the two groups of patients. Thus, the role of the nonorganic signs is difficult to assess.

The length of time that a patient has had LBP appears to increase the likelihood of finding a positive nonorganic signs test. Waddell et al[8] reported that 12% of patients with LBP who were seeing an orthopedist for the first time showed three or more nonorganic signs. The authors reported three or more nonorganic signs in 33% of two different samples of patients with chronic LBP and in 50% of a third sample of patients with chronic LBP. The three samples of patients had all been off from work for many months with a high incidence of previously failed treatments. No positive tests were detected among subjects without LBP. Factors responsible for the increased occurrence of nonorganic findings in patients with chronic LBP have not been identified. The likelihood of finding three or more nonorganic signs may increase with the duration of the problem or because of the failed treatments.

Nonorganic Signs and Tests of Musculoskeletal Performance

Nonorganic contributions to a patient's LBP may coexist with organic contributions. Organic findings may be influenced by nonorganic factors, and in some patients, nonorganic findings may be influenced by organic factors. Waddell et al[22] evaluated the relationship between the presence of the nonorganic signs and 27 tests of musculoskeletal impairments in 120 patients with chronic LBP. Reproduction of the patient's pain during hip and knee movements and limitations in passive knee flexion, hip flexion force, hip abduction force, and prone isometric trunk extension were positive more frequently in the patients who had two or more nonorganic signs (29%) than in the patients who had only one or no nonorganic signs (71%). The only impairments not correlated with a nonorganic component were those related to spinal posture and lumbar flexion. Based on these findings, the authors concluded that the physical tests of musculoskeletal impairments that they investigated were better indicators of illness behavior than of physical impairment.

Groups of patients with LBP with three or more nonorganic signs performed poorer on tests of force production, range of motion, and motor skills than did groups of patients with LBP without nonorganic signs.[23-26] These tests included tests of lumbar range of motion and isometric force on an Isostation B-200 [TM] lumbar dynamometer([dagger])[23,24] and tests of lifting, gripping, and physical dexterity on an ERGOS [TM] Work Simulator.([double dagger])[25] Menard et al[26] found that patients with LBP with nonorganic signs produced lower torques for isometric elbow flexion and isometric knee extension than did patients without nonorganic signs. The authors contended that musculoskeletal performance as measured by dynamometers does not necessarily reflect maximum physical capacity. Low values on any of these tests, however, could not be used to identify individuals with nonorganic problems, because some individuals with a positive nonorganic signs test scored as well as some individuals without nonorganic signs.

Cooke et al[24] measured force and range of motion in patients with chronic LBP, using a lumbar dynamometer. The same test was repeated after 4 weeks of an active reconditioning exercise program. Patients with a positive nonorganic signs test demonstrated improvements in force that were greater than improvements that might be expected as a result of physiologic changes or a learning effect of the test procedure. The authors suggested that the improved force generation might have been due to alterations in illness behavior rather than to an improvement in physical capacity.

Findings that nonorganic components may contribute to measures of musculoskeletal impairments suggest that these measures, which are frequently used by physical therapists for patients with LBP, may also reflect a psychological component of disability. In addition, these data suggest that physical therapists may want to continue measuring musculoskeletal impairments but need to consider the influence of other factors, such as illness behavior, on these tests. Likewise, benefits from treatment focused on physical reconditioning may result in reducing disability by improving an individual's psychological status, and thus his or her tolerance to activity, rather than just improvements in the measurement of musculoskeletal impairments, such as peak torque of the lumbar extensors.

Relationship Between Nonorganic Signs and Treatment Outcomes

Nonorganic phenomena can interact with expected treatment outcomes in patients with LBP. Several investigators[27-29] have described poorer results from lumbar surgery in patients with nonorganic signs. McCulloch[27] found that 97 of 109 patients with a nonorganic component who underwent chemonucleolysis continued to have back or leg pain that prevented their return to full activity. One hundred eighty-six of 327 patients without nonorganic signs, in contrast, were free of pain or had minimal limitations in activity following the chymopapain injection. Dzioba and Doxey[28] found that only 49% of patients with two or more nonorganic signs were approved to return to work by a physician 12 months after various forms of lumbar surgery, as compared with 78% of patients who had only one or no nonorganic signs following surgery.

In a prospective study by Waddell et al,[29] psychological factors, including the presence of a positive test for nonorganic signs, correlated with a poor surgical outcome, as assessed by a physician, the patient, and the patient's work status. A poor surgical outcome in this study was defined as postsurgical episodes of disabling back or leg pain, chronic use of narcotic medications, further surgery, or inability to return to work. Relief from pain and reduced disability depended on the presence of an accurate diagnosis of a surgically treatable pathological condition without the presence of nonorganic signs.

Outcomes of nonsurgical treatments of patients with LBP have also been influenced by the presence of nonorganic signs. Lehmann et al[30] found that electroacupuncture treatment of patients with chronic LBP who had three or more nonorganic signs was no more effective for pain reduction than a sham treatment. In contrast, the authors found that treatment of patients with electroacupuncture, in the absence of nonorganic signs, resulted in a greater decrease in pain than did the sham treatments.

Patients with illness behavior as measured by the presence of nonorganic signs, nonorganic symptoms, and a pain drawing received more treatments than did patients who did not exhibit illness behavior in a study by Waddell et al.[31] These treatments included medication use, lumbar injections, orthopedic supports, physical therapy, spinal manipulation, and bed rest. Based on this finding, a clinician should seriously consider whether there is overutilization of treatments when patients who test positive for nonorganic signs show no progress. For these patients, treatment might be directed toward addressing the illness behavior.

Ability of Nonorganic Signs to Predict Return to Work

A common goal in the rehabilitation of workers with LBP is to return them to work. There is conflicting evidence about the ability to use nonorganic signs for predicting return to work. Bradish et al[32] reported that a positive nonorganic signs test at initial assessment in a group of workers with a low back injury (N = 120) did not correlate with work status between 12 and 18 months after injury. In contrast, Ohlund et al[17] found a relationship (r = .34) between nonorganic signs and the time needed by a group of automobile workers (N=103) to return to work. In this study, return to work was defined as the return to the same job at least half-time.

Lancourt and Kettelhut,[33] in a study of 134 patients with LBP, found that the nonorganic signs of axial loading, simulated rotation, distraction, and a sensory regional disturbance were among the factors that were better predictors of return to work than were ankle and knee reflexes, motor loss, and sensory loss in a dermatomal pattern. This relationship was seen for patients who returned to work within the first 6 months after injury but not for patients who were off work for greater than 6 months. Recently, Kummel[34] described two new nonorganic signs: lumbar pain during isolated cervical movement and lumbar pain limiting active shoulder movement. The presence of these two signs in addition to the presence of three or more of Waddell's nonorganic signs improved the ability to predict patients who failed to return to work in this retrospective study of 717 patients.

The treatment received by injured workers may influence their return to work. Werneke et al[13] evaluated a physical conditioning program designed to meet each patient's job requirement for 170 workers with LBP. One hundred fifteen of the patients showed work status improvement within 3 months of completing the program. At least one nonorganic sign was present in 47% of the patients whose work status did not improve, as compared with 12% of the patients who demonstrated improvement. The number of nonorganic signs present at discharge from the program was reduced for 82% of the patients whose work status improved. In contrast to the high success rate from physical conditioning, when patients with nonorganic findings received treatments described as "symptomatic and at the discretion of the physician," less than 40% returned to work.[32]

Other factors, besides the presence of nonorganic signs, may influence an injured worker returning to previous job duties. Waddell et al[29] found return to work after lumbar surgery was predicted by physical, psychological, and occupational factors. Physical therapists should consider the relationship of these factors in the treatment of injured workers. The referral to an appropriate professional or multidisciplinary team should be made for management of any confounding factors when a patient's work tolerance fails to improve from physical therapy.

Clinical Implications

A physical problem may coexist with the presence of nonorganic signs. Thus, the presence of nonorganic signs does not eliminate the need for a complete physical examination. A patient with a cauda equine syndrome, for example, may be classified as exhibiting nonorganic behavior based on sensory and motor losses and overreaction to the examination because of the intensity of symptoms. Physical examination, however, should identify the structural etiology of the problem, and appropriate treatment should be directed toward the pathological condition.

According to Waddell et al,[8] nonorganic signs by themselves should not be equated with malingering or the presence of a psychological problem. Rather, the finding of nonorganic signs should alert the clinician to the need for more comprehensive testing. Labeling a patient as a malingerer does little to help the patient enhance his or her tolerance for activity. Instead, the factors that are limiting the patient from recovering his or her tolerance for activity should be identified, and interventions should be targeted toward modification of the limiting factors.[5]

Classification of movement dysfunction in patients with LBP may help clinicians to identify individuals who will benefit from specific treatments. Failure to account for the presence of nonorganic findings may lead to the misclassification of patients, because nonorganic factors may influence patients' performance on tests used to classify them. Delitto et al[35] screen for nonorganic signs in their treatment-based classification scheme and suggest referral to an appropriate practitioner when screening is positive. Marras et al[36] developed a classification scheme for patients with low back disorders based on the higher derivatives of trunk velocity. Using this method, Marras et al found that patients with nonorganic findings were distinguishable from patients in nine other low back disorder categories.

The utility of Waddell's nonorganic signs has been described for patients with LBP. To date, nonorganic signs tests for musculoskeletal problems in other regions of the body are not commonly used. Development of nonorganic signs tests for patients with other musculoskeletal problems may help to guide management of these patients.

Nonorganic signs are found more frequently in persons with chronic LBP as compared with persons with acute LBP. Further investigation may reveal how nonorganic behaviors increase and develop in patients with chronic LBP. Treatment focused on prevention of the development of nonorganic signs may reduce the occurrence of chronic LBP and back-related disability.

Summary

The role of Waddell's nonorganic signs test as a screening tool for psychological factors in the examination of patients with low back problems has been described. The presence of nonorganic signs should alert the physical therapist to the need for additional psychological tests and should not necessarily be considered an indicator of malingering. Nonorganic signs may coexist with organic findings. An illness behavior role of the nonorganic signs is suggested, as they have been related with disability in addition to physical impairments. Physical therapy management for these patients should focus on treatment of illness behavior and on combating disability.

Acknowledgments

I thank Louise J White, PT, and Pamela J Woodall, PT, for their kind assistance with the preparation of this update.

(*) The seven other instruments were a pain drawing, the Modified Somatic Perception Questionnaire, the Hospital anxiety Scale, the Hospital Depression Scale, the Zung Depression Scale, the Illness questionnaire, and a nonorganic symptoms test.

([dagger]) Isotechnologies Inc, 328 Elizabeth Brady Rd, PO Box 1239, Hillsborough, NC 27278.

([double dagger]) Work Recovery Inc, 2341 S Friebus, Suite 14, Tucson, AZ 85713.

References

[1] Spitzer WO. Diagnosis of the problem (the problem of diagnosis): scientific approach to the assessment and management of activity-related spinal disorders--a monograph for clinicians: report of the Quebec Task Force on Spinal Disorders. Spine. 1987;12:S16-S21.

[2] Waddell G, Main CJ, Morris EW, et al. Chronic low-back pain, psychologic distress, and illness behavior. Spine. 1984;9:209-213.

[3] Delitto A. Are measures of function and disability important in low back care? Phys Ther. 1994;74:452-462.

[4] Bigos S, Bowyer O, Braen G, et al. Acute Low Back Problems in Adults: Clinical Practice Guideline No. 14. Rockville, Md: Agency for Health Care Policy and Research, Public Health Service, US Department of Health and Human Services; 1994. AHCPR publication 95-0642.

[5] Feuerstein M, Beattie P. Biobehavioral factors affecting pain and disability in low back pain: mechanisms and assessment. Phys Ther. 1995;75:267-280.

[6] Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Washington, DC: American Psychiatric Association, 1994.

[7] McCahill ME. Somatoform and related disorders: delivery of diagnosis as first step. Am Fam Physician. 1995;52:193-203.

[8] Waddell G, McCulloch JA, Kummel E, Venner RM. Nonorganic physical signs in low-back pain. Spine. 1980;5:117-125.

[9] Waddell G, Richardson J. Observation of overt pain behaviour by physicians during routine clinical examination of patients with low back pain. J Psychosom Res. 1992;36:77-87.

[10] Collie J. Malingering and Feigned Sickness. London, England: Edward Arnold (Publishers) Ltd; 1913.

[11] Hoover CF. A new sign for the detection of malingering and functional paresis of the lower extremities. JAMA. 1908;51:746-747.

[12] Greenough CG, Fraser RD. Comparison of eight psychometric instruments in unselected patients with back pain. Spine. 1991;16: 1068-1074.

[13] Werneke MW, Harris DE, Lichter RL. Clinical effectiveness of behavioral signs for screening chronic low-back pain patients in a work-oriented physical rehabilitation program. Spine. 1993;18:2412-2418.

[14] McCombe PF, Fairbank JCT, Cockersole BC, Pynsent PB. Reproducibility of physical signs in low-back pain. Spine. 1989;14:908-918.

[15] Solomon PE. Measurement of pain behaviour. Physiotherapy Canada. 1996;48:52-58.

[16] Keefe FJ, Block AR. Development of an observation method for assessing pain behavior in chronic low back pain patients. Behav Ther. 1982;13:363-375.

[17] Ohlund C, Lindstrom I, Areskoug B, et al. Pain behavior in industrial subacute low back pain, part I: reliability--concurrent and predictive validity of pain behavior assessments. Pain. 1994;58:201-209.

[18] Waddell G, Pilowsky I, Bond MR. Clinical assessment and interpretation of abnormal illness behaviour in low back pain. Pain. 1989;39:41-53.

[19] Main CJ, Wood PLR, Hollis S, et al. The Distress and Risk Assessment Method: a simple patient classification to identify distress and evaluate the risk of poor outcome. Spine. 1992;17:42-52.

[20] Chan CW, Goldman S, Ilstrup DM, et al. The pain drawing and Waddell's nonorganic physical signs in chronic low-back pain. Spine. 1993;18:1717-1722.

[21] Hayes B, Solyom CAE, Wing PC, Berkowitz J. Use of psychometric measures and nonorganic signs testing in detecting nomogenic disorders in low back pain patients. Spine. 1993;18:1254-1262.

[22] Waddell G, Somerville D, Henderson I, Newton M. Objective clinical evaluation of physical impairment in chronic low back pain. Spine. 1992;17:617-628.

[23] Hirsch G, Beach G, Cooke C, et al. Relationship between performance on lumbar dynamometry and Waddell score in a population with low-back pain. Spine. 1991;16:1039-1043.

[24] Cooke C, Menard MR, Beach GN, et al. Serial lumbar dynamometry in low back pain. Spine. 1992;17:653-662.

[25] Cooke C, Dusik LA, Menard MR, et al. Relationship of performance on the ERGOS work simulator to illness behavior in a workers' compensation population with low back versus limb injury. J Occup Med. 1994;36:757-762.

[26] Menard MR, Cooke C, Locke SR, et al. Pattern of performance in workers with low back pain during a comprehensive motor performance evaluation. Spine. 1994;19:1359-1366.

[27] McCulloch JA. Chemonucleolysis. J Bone Joint Surg [Br]. 1977;59:4552.

[28] Dzioba RB, Doxey NC. A prospective investigation into the orthopaedic and psychologic predictors of outcome of first lumbar surgery following industrial injury. Spine. 1984;9:614-623.

[29] Waddell G, Morris EW, Di Paola MP, et al. A concept of illness tested as an improved basis for surgical decisions in low-back disorders. Spine. 1986;11:712-719.

[30] Lehmann TR, Russell DW, Spratt KF. The impact of patients with nonorganic physical findings on a controlled trial of transcutaneous electrical nerve stimulation and electroacupuncture. Spine. 1983;8: 625-634.

[31] Waddell G, Birchner M, Finlayson D, Main CJ. Symptoms and signs: physical disease or illness behaviour? BMJ. 1984;289:739-741.

[32] Bradish CF, Lloyd GJ, Aldam CH, et al. Do nonorganic signs help to predict the return to activity of patients with low-back pain? Spine. 1988;13:557-560.

[33] Lancourt J, Kettelhut M. Predicting return to work for lower back pain patients receiving worker's compensation. Spine. 1992;17:629-640.

[34] Kummel BM. Nonorganic signs of significance in low back pain. Spine. 1996;21:1077-1081.

[35] Delitto A, Erhard RE, Boling RW. A treatment-based classification approach to low back syndrome: identifying and staging patients for conservative treatment. Phys Ther. 1995;75:470-489.

[36] Marras WS, Parnianpour M, Ferguson SA, et al. The classification of anatomic- and symptom-based low back disorders using motion measure models. Spine. 1995;20:2531-2546.

DA Scalzitti, PT, OCS, is Clinical Instructor, Department of Physical Therapy, University of Illinois at Chicago, 1919 W Taylor St (M/C 898), Chicago, IL 60612-7251 (USA) ([e-mail]), and Specialist in Physical Therapy, Department of Physical Therapy, University of Illinois Hospital, Chicago, IL 60612-7233. Address all correspondence to Mr Scalzitti at the first address.