What Causes Loss Of Lordotic Curvature?

Loss of normal lordotic curvature. No spondylolysis or listhesis.
At L4-5 disc level, there is advance disc desiccation associated with disc herniation which is diffuse extends to both sides more towards the Rt.and also extends inferiorly beyond the endplate, maintained by the posterior long. ligament, compress on the thecal sac and the transversing nerve roots including L5 nerve root.
At L5-S1 disc level, there is advance disc desiccation associated with disc protrusion which is again diffuse but mainly central effaces the epidural fat and minimally indenting on the thecal sac, associated posterior osteophytic spurring is noted. No displacement or significant compression on the nerve roots seen at this level, if anything slightly abutting the S1 nerve root without displacement.
The remainder of the disc spaces showed no disc herniation. No significant central canal stenosis apart from above described mild discogenic narrowing.
No destructive changes. No facetal hypertrophy or narrowing of the lateral recesses.
Normal conus medullaris and paraspinal soft tissue