Mri lumbar spine... There is mild facet hypertrophy of l4- L5 and l5-s1 bilaterally. Impression: mild facet of l4-l5 and l5-s1. Pkease explain..

Normal. Nothing to worry about . Essentially normal finding . Usually won't cause big problems.
Degenerative changes. As the spine ages the intervertebral disks can provide less stability. This causes more pressure on the facet articulations at the back of each vertebral body. They respond by broadening or hypertrophying. Usually this is asymptomatic but can sometimes cause back pain and stiffness.