Recent mri due to left leg pain and weakness in back of thigh calf and foot. results show no herniated disc. so painful walking standing sitting! help?

MRIs are not magic: You need to see a talented specialist in the orthopedic spine issues to evaluate your problem. Just having an MRI does not necessarily mean that's nothing is wrong. If all tests are negative and the spine specialist does not feel your problem is back related then you would probably want to see a regular ortho for the leg. The MRI is just one tool for a orthopedic specialist to use, and it's not a substitute for a good clinical examination and history.

MRI: Which part of the body was the MRI performed? It should be have been done at the lumbo sacral region of your low back. Sound like a nerve root compression. You may require an epidural block. Apply ice to your low back to see if symptoms improve for now along with an anti inflammatory for pain if not allergic.