Yes, an MRI would definitely be indicated in your case and you should probably get one done. X rays show only the bony abnormalities and do not tell us anything much about nerve root compression
which is the cause of sciatica
, weakness, etc. An MRI would give these details.
Subluxation indicates movement of one vertebra over the adjacent (I'm assuming it is anterior subluxation of L4 over L5) and retrolisthesis
means backward movement of the vertebra over the lower one (L3 over L4). These are usually due to break in the posterior vertebral
portion (lysis) or due to facetal arthropathy, both of which are not mentioned in your X ray report.
Subluxation/listhesis often leads to compression of nerve roots and needs to be operated if symptoms are severe. You would need to meet an orthopedic surgeon to discuss your options. Till then, avoid lifting heavy objects, doing heavy work, etc and wear a lumbar support (belt) if you have one.