There are many conditions, like Guillain-Barré Syndrome, that can eventually lead to muscle and especially leg weakness.
Sudden leg weakness. Where is the problem? What is the cause?
Low back pain - acute Information
The Benefits of Working Out At Home
Not all low back pain is the same - Mayo Clinic Health System
Stroke Signs and Symptoms
4 leg problems and what might be causing them - Harvard Health
Weakness in Legs: 10 Causes & What to Do - Tua Saúde
Weakness - Brain, Spinal Cord, and Nerve Disorders - MSD Manual Consumer Version
SCIATICA AND LEG WEAKNESS: A WORRYING COMBO