The SIJ is 20 times more vulnerable to axial compression failure and twice as susceptible to axial torsion overloading than are the lumbar motion segments. Imbalanced or unilateral loads may jeopardize the interlocking sacral mechanics by impeding balanced transiliac bony fixation and ligamentous tension across the “keystone”. Miller et al. discovered a threefold increase in sacral rotation with both ilia fixed versus a 2- to 8-fold increase in sacral rotation upon loading with one ilia fixed. Hence, athletes and workers participating in activities requiring repetitive, unidirectional pelvic shear and/or torsional forces (e.g.,figure skaters) may have a higher propensity to develop sacroiliac joint dysfunction.