I have had a decent response from glucosamine, in only about a month.
All I have read tells of waiting three months or more for an improvement, but Renaeden (I think it was) told me that it had helped her much faster.
I have to agree. My funky hip injury has mostly cleared up and my back is better, even considering I have just fended off a cold.
I have no higher recommendation to make for joint pain, assuming you get plenty of exercise already.