IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFULL
PRAISE BE UPON HIM, THE ONLY ONE GOD
well, i can understand how it feels.i also had a grandmother like his condition.
first, we must know the diagnose of his disease. and i suspect it is rheumatoid arthritis
and some differential diagnoses.and then after decide diagnose,we give the medicine.but I am so afraid of his age.because synthetic medicines have some contraindication and so related with liver
and renal function which we know that in that age, he has lower and lower function of liver and renal.so i suggest to consume herbal product namely habbatus sauda as Rasulullah Muhammad saw.says:
"Actually, in the habbatus sauda, you can find medicine that can cure all diseases except death."
you can find that product in near supermarket.and blend it with some honey and milk.honey is medicine as the Holy Qur'an says.
I hope you can try all truth from hadist Rasulullah saw and from the holy Qur'an.
praise be upon ALLAH, THE ONLY ONE GOD.