Welcome to HealthcareMagic.Knee pain
at your father's age could be praobably of some arthritic origin. Hope of all investigations, he has been investigated well for Gout as well. Because , this is very common about this age.He might be having osteoarthritis
could or it could even be a tendinitis
. Well that also reminds me that, at this juncture, if he hasnt got any pain relief, need to look for some systemic cause too, like any malignancy so to say... multiple myeloma
.So i would suggest, if he had been seen only by an orthopedician all this while, then he might be taken to a rheumatologist
or a physician for that matter.Thank you.