There are a lot of elder females in Japan who have problem on their knees. It is "knee osteoarthritis", "henkei-sei-shistu-kansetsu-shou"（変形性膝関節症）in Japanese. My mother is one of them.
She developed this problem about 4 years ago. The pain on her right knee had grown day by day and finally she could not walk smoothly. About three months of nursing my father might make her condition worse.
I had recommended her to see a doctor in a relatively big hospital and receive an advice about an operation to replace her knee with an"artificial joint" but she didn't. But she decided to go to a hospital when she felt a strong pain in her knee in the middle of February.
The doctor explained her that Total Knee Arthroplasty ( TKA ) is the most effective way to get rid of her pain, and she agreed. Now, she is in the hospital (ironical speaking, it is where my father died!) and will receive the operation next week. I really hope her success in the operation.