31 year old construction

worker complains of intensive low back pain, irradiating to the lateral side of

the left foot. Pain worsens with motion of spine. Examination: lumbar muscles

are tense, more on the left, no muscle weakness, patellar reflexes R=L,

Achilles reflexes R>L, positive straight leg rise at 40* at the left.

Provide the diagnosis (name exact structure of peripheral nervous system

affected) and most appropriate treatment.