Objective: To determine sacroiliac joint compliance characteristics and pelvic floor movements in older women relative to gynecological surgery history and back pain complaints. Design: Single-visit laboratory measurement. Setting: University clinical research center. Participants: Twenty-five women aged 65 years or older. Outcome Measures: Sacroiliac joint compliance measured by Doppler imaging of vibrations and ultrasound measures of pelvic floor motion during the active straight leg raise test. Results: Doppler imaging of vibrations demonstrated test reliability ranging from 0.701 to 0.898 for detecting vibration on the ilium and sacrum sides of the sacroiliac joint. The presence of low-back pain or prior gynecological surgery was not significantly associated with a difference in the compliance or laxity symmetry of the sacroiliac joints. No significant difference in pelvic floor movement was found during the active straight leg raise test between subject groups. All P values were .4159. Conclusions: Prior gynecological surgery and low-back pain were not significantly associated with side-to-side differences in the compliance of the sacroiliac joints or in significant changes in pelvic floor movement during a loading maneuver in a group of older women.Keywords aging, back pain, gynecologic surgery, sacroiliac joint, pelvic floor, Doppler imaging of vibrations Extensive low-back pain (LBP) research has modeled lumbopelvic stability derived from both global (multisegmental) muscles and more local or single-segment muscles. 1 A control system model integrated the active anatomic elements, passive anatomic elements, and the arthrokinetic control elements (sensory afferents; spinal, subcortical, and cortical neurons; efferent motor elements). 2,3 These models fostered extensive investigation into neuromuscular control and stability of the lumbopelvic junction with early observations of altered motor control in specific muscles in LBP populations 4-7 with rapid carryover into rehabilitation efforts focused on neuromuscular reeducation of the deep abdominal and pelvic floor muscles, part of the so-called core stability system, in LBP populations. 8,9 The abdominal wall muscles are postulated to contribute to lumbopelvic stability in part due to linkage with the thoracolumbar fascia system. 10 Deep abdominal muscles were observed to have altered activation patterns in chronic LBP populations during specific load challenges compared with normal populations. 5,6,11,12 Further work described similar premovement activation implicated as postural contributions to spine stability, in the pelvic floor muscles, deep fibers of the multifidus muscle, and the respiratory diaphragm. [13][14][15][16][17][18][19][20][21][22] Altered neurophysiological control of pelvis and abdominal muscles using electromyographic, ultrasound, athletic performance, and postural measures has been linked to LBP conditions. 11,[23][24][25][26][27] These observations of changes in muscle neurophysiological control in LBP populations, combined ...