It’s very likely that your mother has what is called limited joint mobility or LMJ. This could be mistaken for arthritis if you’re looking at her hands and how she is limited as to how she can bend her fingers. However, this is a different issue. In LMJ, there doesn’t seem to be pain, just the inability to straighten out the fingers as much as before. For example, if someone without LMJ or any joint problems puts their hand palm down flat on a table, their fingers would naturally spread out as the hand goes flat. For someone with LMJ, if they put their hand flat, their fingers won’t spread out and they can’t put their fingers and palm on the table at the same time.