I wouldn't have thought it would be that uncommon to have the leg weakness that makes you fall.

Many many years ago I was unable to use my legs properly.
I had bulging discs at L3/L4 L4/L5 and L5/S1.

It was also found at the time that I had sliding S1 - Spondylolisthesis.
The sliding S1 caused a lot of instability and particularly with the already terrible muscle and ligament spasms I had above it and around the whole lumbar area. I also have hypermobility problems so that didn't help.

I had a wonderful physiotherapist who literally used to come to my bed and half carry me to her car and take me to a hot water swimming pool. ugh, those were horrible days. I didn't ever have surgery... I'm going back 30 years now. I had been laying pavers and rolling out turf and doing ridiculous things considering the state of my spine but all that was unknown to me at the time until I wound up in bed unable to walk and with numb toes.