What is a good treatment for calcium buildup in knee joints?

Several things: Chodrocalcinosis is calcium deposits in the cartilage, which can cause pseudogout, a type of arthritis or rheumatism. It is now known to be associated with primary or secondary hyprparathyroidism, the latter most associated with vitamin d defiency. You need an evaluation by someone in rheumatology to both treat the condition and determine cause.