Brief Answer:
Chronic lower limb ischemia
Detailed Answer:
Hello!
Thank you for the query.
The problem is most likely caused by Chronic lower limb ischemia due to
atherosclerosis. As she is over 90, her arteries are narrowed due to
cholesterol accumulation in the arteries walls. This causes lack of blood circulation in some arteries, some gets closed.
The typical symptoms of such ischemia are pale, cold limb with pain and numbness. The pain usually appears after walking (depending of the distance we can set a level of ischemia).
Her symptoms can be also caused by arteries obstruction due to
embolism. The difference is that the symptoms appear suddenly, the foot gets pale, pulse less, painful,
paresthesia appears. If not treated the limb gets dark or black, pain goes away.
As your mothers foot has not gotten black and become warm, obstruction is less probable.
I suggest her to have arteries
ultrasound of this leg and consult vascular surgeon.
Hope this will help. Feel free to ask further questions.
Regards.