One should condsider that the lower limb nerves run through the thing, left and foot. I would get your physio to look for possible sites of entrapment in those areas. Perhaps some neural testing and posturing will highlight where the tract is getting blocked. Releasing this (joint, fascial tension etc) might well resolve the big toe issue.

In summary don't just blame the back itself as we all (well most of us) exhibit those changes you mention on your Wikipedia reference-linkMRI. One might say in fact that they are pretty darn normal.