This needs a detailed evaluation of your mother’s horoscope using strength of planets, houses and the Mahadasas, antardasas etc. You will have to come through paid consultation to get any advice from us based on the evaluations. These days joint replacements are done by steel rods and kneecaps and similar screws etc. Such a case for the doctor makes him very rich. Astrologers are not competent to diagnose whether the joints need replacement or not.
For contacting a doctor one does not need astrological clearance. An astrologer need be consulted if you need to evaluate a horoscope for which you will have to pay for. Otherwise you can contact a wayside astrologer.