A radiostereometric analysis of the movements of the sacroiliac joints in the reciprocal straddle position

Study design. A radiostereometric analysis of the reciprocal straddle position. Objectives. To evaluate the magnitude of rotation in the sacroiliac joints in the reciprocal straddle position. Summary of Background Data. the reciprocal straddle has been objectified in different studies, using different techniques, to show a sacroiliac motion between 5 degrees and 36 degrees. Previous studies with radiostereometric analysis during different provocations reported much smaller movements. Methods. Six women with posterior pelvic pain of long duration after pregnancy (n = 5) and sacroilitis (n = 1) underwent radiostereometric analysis in the sustained reciprocal straddle position. Results. A reciprocal movement could be demonstrated in the sacroiliac joints in the reciprocal straddle position. However, the movements were 10 times smaller than reported in earlier studies of the reciprocal straddle position. Conclusions. It was possible to demonstrate reciprocal movements of the sacroiliac joints in the straddle position. However, the radiostereometric analysis technique showed the movements to be small, as reported in other mobility studies.