SI•RX was developed specifically to mobilize SI joints. SI joints, or sacroiliac joints, are the joints between your sacrum, the triangular shaped bone at the base of your spine, and either side of your pelvis. They are irregular joints and represent the junction between upper and lower body. As such, they are common areas of dysfunction, frequently leading to back, buttock, pelvis, hip, and knee pain. In order for SI joints to function efficiently, they need to be aligned properly and they need to be mobile. Regular use of SI•RX helps maintain SI joint alignment and mobility.