So your mother is suffering from Knee osteoartheritis. The need for joint replacement
arise when the joint is fully damaged and pain interferes with daily activities. This surgery has 95% good results.
For lesser damaged knees, there are alternatives in the form of Intraarticular stem/Activated platelet therapy.
But only your doctor, after seeing ur mother and x rays, can advise u on the feasibility and success of the alternative methods.
If not, 67 years is still young. And i will advice to to give joint replacement surgery a second thought. It has shown to improve the quality of life.
You can contact me, in case u require any further help.
Bye. Wish ur mother best of health.