How often is low back pain not coming from the back?

STUDY DESIGN.: Consecutive case series cohort. OBJECTIVE.: To determine the relative frequencies of the spine, the sacroiliac (SI) joint, and the hip joint being the primary pain generator among patients presenting at a spine surgery clinic for low back pain (LBP). SUMMARY OF BACKGROUND DATA.: Identification of the primary pain generator in a patient with LBP is difficult. Possible pain sources include the lumbar spine, the SI joint, and the hip joint. Their relative frequencies among patients presenting at a spine surgeon's clinic have not been well established. METHODS.: Three hundred sixty-eight new patients were seen at a single spine surgeon's clinic during a 10-month period. Of these, 289 (78.5%) complained primarily of LBP with or without leg pain. Seventy-seven had previous surgery. The remaining 200 cases were reviewed for all diagnostic tests performed, as well as the final diagnosis. RESULTS.: One hundred sixty-four (82%) had spine pathology, but only 130 (65%) had spine-only pathology, whereas 35 (17.5%) had a combination of spine plus hip and/or SI joint pathology. An additional 16 (8%) had hip and/or SI joint pathology without spine pathology. Twenty (10%) had an undefined pain source. Overall, 25 (12.5%) had hip pathology, and 29 (14.5%) had SI joint pathology. CONCLUSION.: For patients presenting to a spine surgeon's clinic for LBP, up to 25% of patients may have significant pain contribution from the hip or SI joints, and an additional 10% will still have an undefined pain source even after diagnostic workup. This underscores the need for clinicians to be aware of nonspinal pain generators and to appropriately pursue alternative diagnoses.