In 25 patients of both sexes who suffered from coccygeal syndrome the authors examined the function of sacro-iliac joints in all directions before and after traction of the muscles of the pelvic floor per rectum. The results of this clinical study and comparison with results of previous objectivating studies using the optic method of shadow moiré revealed that dextrolateral traction of the muscles of the pelvic floor alters the position of the sacral bone which is drawn in caudal direction against the iliac bones, its lower end is drawn to the right side, its upper end is as a compensation shifted to the left side and rotation round the vertical axis occurs and the right margin of the bone is in a more ventral position than the left margin.

        Key words: pelvic floor muscles, m. coccygeus, coccygeal syndrome, dysfunction of the sacro-iliac joint, position of the sacral bone