MSM was already mentioned, but you might consider consuming large quantities of it, working up to as much as half a cup a day. Many folks like myself buy animal-grade MSM (eg. from Amazon) which is fine for humans, and this way it's dirt cheap. If the MSM does not help no matter, it has lots of other benefits. It is supposed to be anti-inflammatory.
Another dirt cheap option is to try a Godzilla zapper on the knee. It basically consists of a large 6v battery connected to wet sponges via wires. Info is on the following Yahoo group, but I can send you info if you like. http://health.groups.yahoo.com/group/microelectricitygermkiller/ -- Alan Jones "The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people." (Tenth Amendment to the US Constitution)