Most common reason for knee pain in old age is osteoarthritis only. Severe osteoarthritis can be associated with severe pain and swelling too. Permant solution for sever osteoarthritis knee is joint replacement only
Next Steps
Looking at current circumstances it might not be safe for her to undergo surgery immediately. so she can follow precautionary measures e.g. to avoid squatting, cross leg sitting, climbing stairs
Health Tips
use knee cap/ knee brace, ice pack application, dolo 650....2 times