To have your sacrum fused to the iliac(s) while having fused joints high up the spine, simply transfer any bending to your hips joints. So not only bending but weight of the upper torso or lifting. A gallon of water is 7lbs so it adds up quickly. How fast will hip sockets wear out? Not me as my root cause is muscle tissue was damaged and now scar tissue. A pain pump trial is in my future after 14 years of chasing this. Medical care can move very slow yet SI injection removed bottom 1/3 of pain, but still only lasted 7 weeks. L4-L3-L2 epidural lasted 1 1/2 days. All resulting from 5hrs of heavy lifting & straining low back muscles. I went from feeling fine to waking up to a blistered sunburn pain overnight.