From history it seems that your mother might be having Osteo-artheritis of both knee joints.
From symptoms it seems that she might require joint replacement
surgery of both the joints.
Consult orthopedic surgeon and get examined.
Mean while ask her to go for patellar exercise and other physiotherapy
Avoid more bending from the joint.
Do not ask her to squat, use commode latrine.
Give her calcium, vitamin A
and D supplements.
Ok and take care.