My uncle has thickened nerve root on right side at l5/s1 level. he can't sit and stand properly. almost a year his situation is like that, already take some medicines that his doctor wrote but still there's no effect. what should we do?

If there is no surgical option, he should probably go to physical therapy. The physical therapist can help him compensate for his problem so he can learn to sit and stand again, perhaps in a different way. They can also recommend a brace, if needed. So, he should see his doctor for a physical therapy evaluation and treatment. Good luck to both of you!

Has he had spinal surgery which is the usual cause of nerve root thickening? If so, it's a nondiagnosic finding. Otherwise the issue here is whether he's experiencing radicular symptoms. An MRI with contrast showing enhancement of that thickened root is good evidence that it's the cause of symptoms. See a neurosurgeon who will take a good history,perform a thorough examination & review the MRI