Unfortunately, your letter doesn't contain enough information for me to even try and give a diagnosis. However, Alzheimer's doesn't usually cause pain in the legs, so I think something else
is going on. You do not say how far along your mother is in her Alzheimers, so I don't know how reliable her version of the story is, but it sounds like she can tell you she has pain at the very least. It also sounds like it is happening in both legs. So, so here are the questions I would ask a person if I heard about pain in their legs:
1) Circulation problems: Does it occur when walking? Does it stop when you rest?
2) Muscle cramping: Does it feel like leg cramps? Does massage or heat make it better?
3) Neuropathy: Does your mother have diabetes or back problems?
4) Injury: Did your mother fall or injure her legs? Are they swollen, bruised, or difficult to move?
5) Arthritis: Is the pain worse in the morning, better after she has been up for a while?
Once you ask yourself these questions, I would give her healthcare provider a call. They may want to examine her to see what is going on with her legs, and perhaps prescribe some treatment, like pain medication or therapy. Good luck.