I have low back pain & down the back of my lt leg to my knee. an mri showed occult sacral meningocele. could this be the cause?

These typically are: Incidental or accidental findings on some patients' mri's as they occur usually without any symptoms except in older patients with bone density loss and when large can cause bone erosion sometimes leading to a sacral fracture but otherwise of no consequence and most likely unrelated to your symptoms. See a spine specialist for a specific evaluation.