Problems with thyroid
leads to mental instability and it has nothing to do with arthritis
. As the age is 60yr which is commonly associated with arthritis. In this case my suggestion is to test for thyroid and start treatment accordingly. For arthritis she has to take rest, a little walking exercise in a garden is good for both mental stability and for joint pains
. She can wear knee cap to keep it warm and take painkillers to relieve pain if necessary but under supervision.