Evidence for sacroiliac disease as a common cause of low backache in women. 
99M Tc stannous pyrophosphate bone scanning with quantitative sacroiliac scintigraphy (Q.S.S.) has been used in 50 females with low backache and in 66 symptomless female controls.  Mean uptake of radionuclide at the sacroiliac joints was significantly increased in the patients when compared with controls.  Q.S.S. gave objective evidence of unilateral sacroiliac disease in 2 of the 66 controls compared with that of unilateral and bilateral sacroiliac disease in 8 and 14 of the 50 patients respectively.  Of the 22 patients with abnormal scans, 20 had normal radiographs.  An abnormal scan did not correlate with the presence of HLA B27.  It is concluded that sacroiliac disease is a common cause of low backache in women, and that it can be objectively diagnosed by Q.S.S. when radiographs are normal.