1. It seems your mother is suffering from age-related osteo-arthritis
of the spine,
2. Forward slipping of L4 over L5 vertebra is called anterolisthesis. Sideways curving of spine is called as scoliosis
. Since both are minimal, they can be age-related changes / osteo-porosis.
3. SI = sacro-iliac joints. These are the joints connecting the spine / sacrum
with the pelvic bone.
4. If your mom is suffering from pain in low back more on lifting objects / on prolonged forward leaning posture = indicates instability at L4 and L5 segment ---> then you might need CT-scan to find there is any defect in the spine and MRI to rule-out any nerve compression / canal stenosis / associated disc disease
5. If she is otherwise able to tolerate pain, then few analgesics along with calcium supplements