Diagram specific to sacroiliac joint pain site indicated by one-finger test

The sacroiliac joint (SIJ) can be a source of low back and lower limb pain. The SIJ pain can originate not only from the joint space but also from the ligaments supporting the joint. Its diagnosis has been difficult because the physical and radiological examinations have proved less than satisfactory. Thus, to know the specific sites of SIJ pain, if these exist, could be very useful for making the diagnosis. The purpose of the present study was to identify the main site of SIJ pain according to the patient's pointing with one finger and to confirm the site by a pain-provocation test and periarticular lidocaine injection. Forty-six of 247 consecutive patients with low back pain at our outpatient clinic, who could indicate with one finger the main site of the pain, which presented at only one site and was reproducible, were the subjects of this study. The main site of pain was anatomically confirmed by fluoroscopy. Then, a periarticular SIJ injection was performed. The patients were blindly assessed and a diagram of the main site of the SIJ pain was made. There were 19 males and 27 females and the age averaged 50 years. Eight patients showed a positive placebo response and were excluded from this study. Twenty-five of the remaining 38 patients indicated the main site of pain at the posterior-superior iliac spine (PSIS) or within 2 cm of the PSIS, and 18 of these patients showed a positive effect with periarticular SIJ block. The other 13 patients, including 2 patients with a positive response to the periarticular block, did not show the PSIS as the main site of pain. Our study clearly indicated that when patients point to the PSIS or within 2 cm of it as the main site of low back pain, using one finger, the SIJ should be considered as the origin of their low back pain.