My 83-year-old mother has osteoarthritis and her knees are basically bone-on-bone. She is having trouble getting out of her chair. Right now she rocks back and forth in her chair and grabs on the walker, but I'm afraid she's going to keep going and fall head over heels when I'm not there.
May I suggest that when you assist your mom, do not pull on her hands or arms, they are easily dislocated. Help her to move her rear end to the front edge of the chair and put her knees over her feet. Better body mechanics will help her stand up easier. Make sure the chair isn't too low to the ground. Make sure it isn't a rocking chair that works against her. There are also portable seat risers available online. That may have an advantage in that it can be moved from chair to chair.
Cortisone shots in the knees may help, as well as ice packs to reduce swelling. Unfortunately, there really isn't much that can be done. The Supartz shots did nothing for my MIL even though we tried them several times. I now have the same diagnosis and can relate to the pain.
Couple tips about the chairs. They are simple to operate but people with dementia may not be able to remember how. Also, if cognitive skills are bad they can dump themselves on the floor.
My mom does not have dementia but still forgets to use the assist to get up and down most of the time.
My mother had a lift recliner that she spent a lot of time in with her legs up to help reduce swollen calves and ankles. Whether getting into the reclining position or getting out of it - mom was continually punching a hole in the wall behind her with the top corner of the chair. This was while she lived in a NH and they kept patching the wall even though we told them it was fine to leave - since we knew it would just keep occurring. When mom passed and we were settling the account the NH kept the hefty damage deposit- citing having to continually patch the hole in the wall! (Sigh)
One time when Mom was getting PT, he showed me how to help her do things, how she could help herself, how to use a gait belt. Later they showed me how to transfer her without injuring myself. But videos are helpful too.
These chairs come in different sizes, the store asked how much did my Dad weigh and how tall was he, thus he got a chair that was a perfect fit. Later down the road, I could purchase a brand new chair or buy the rented chair with a nice discount.
That chair made it so easy for my Dad to stand up, as in the past he would try to use the arms of his standard recliner or grab the rolling walker seat and try to pull himself up. He fell a few times trying to do that.