Predicting Patients' Response to Spinal Manipulation

Inclusion Criteria: * Age 21 to 55 * Idiopathic mechanical low back pain (LBP) matching classification 1-4 of the Quebec Task Force. * LBP classified as subacute (onset 4-12 weeks previous) or chronic (onset more than 12 weeks previous), with the current episode occurring at least four weeks prior to the date of contact with the clinic: In order to exclude the greatest proportion of LBP patients that have a favorable natural history of improvement. * Written Informed Consent * A minimum baseline score on the Roland Morris Disability Questionnaire (RMQ) of 6 points. Exclusion Criteria: * LBP from other somatic tissues as determined by history, examination, and course (e.g. pain referred from visceral conditions). * LBP diagnosis not meeting Classifications 1 through 4 of the Quebec Task Force, especially the following: low back pain associated with frank radiculopathy defined as typical shooting leg pain; positive straight leg-raising test; an altered lower extremity reflex; a dermatomal sensory deficit; at least one of the following: progressive unilateral muscle weakness or motor loss, or symptoms of cauda equina compression; and CT or MRI evidence of related anatomical pathology (e.g. abnormal disc, stenosis). * Co-morbid pathology or poor health conditions in patients; Co-morbid conditions and general poor health significantly complicate the prognosis of LBP, and inject a variety of uncontrollable factors in case-management, not to mention experimental analysis and interpretation. Patients who have case histories and physical examination findings indicating other that average good health will be excluded from the study. * Bone and joint pathology contraindicating patient for SM of the lumbar spine and pelvis: Patients with spinal fractures, tumors, infections, arthropathies, and significant osteoporosis will be referred to appropriate health care. * Other contraindications for SM of the lumbar spine and pelvis (e.g. bleeding disorders or anticoagulant therapy, extreme obesity). * Retention of legal advice related to this or a previous LBP episode: Patients with occupational or personal injuries will not be automatically excluded from the study unless they answer yes to a specific question about the retention of legal advice with respect to their LBP episode at the baseline interview. * Pregnancy: Pregnancy is a contraindication for exposing a patient to ionizing radiation and is a confounding factor in the usual course of LBP. * Inability to read or verbally comprehend English. * Clear evidence of narcotic or other drug abuse as determined by history and examination: injects significant confounding factors with respect to internal validity and feasibility. * Major clinical depression: Patients with scores greater than 17 on the Beck Depression Inventory will be excluded from the study. Patients with evidence of other psychiatric disorders as determined by history and exam will also be excluded. * Use of manipulative care for any reason within the past 3 months as determined by history: to exclude the possibility of carryover effects. * Unwillingness to postpone use of all other types of manual treatment for LBP except those provided in the study (including chiropractic and osteopathic SM, physical therapy, and massage) for the duration of the study period: to eliminate confounding effects.