The glucosamine is a good start.
Is she declawed?
One of the first things I would suggest if she isn't declawed is to her toes for curled toenails that could be in the nail bed. This happens often in older cats and could be an issue. Also, check between the pads of her feet for litter that could be stuck.
Don't forget to check her dewclaws either (thumbs).
If none of these are an issue I would keep an eye on her and make sure she is eating and drinking normally. There could be an electrolyte imbalance and I would then suggest bloodwork and a possible radiograph of that limb to be sure there are no issues internally.
Please let me know if further assistance is needed.
Thanks Teresa. she is not declawed. I trim her nails monthly. I use feline pine for litter, so nothing between the toes. her appetite and fluid intake is probably to much. thanks for the suggestions...