Nine cases of sacro-iliac pyarthrosis are presented. The difficulty in
localizing the infection is attributable mostly to failure to appreciate
the posteriorly situated physical findings. This, and the difficulty with
early roentgenographic demonstration of the lesion, may lead to unnecessary
abdominal exploration (as in two of our patients) or to prolonged delay in
diagnosis and hence spread of the infection. Awareness of the usual
physical findings and prompt use of radioisotope scanning to localize the
infection led to earlier diagnosis and avoidance of surgery in three
patients seen recently. Antibiotic therapy, with or without surgery, led to
cure in all patients, with minimum sequelae.