I got something very similar to what Scott descibes. I had a scrape on my elbow and was fishing in the Yakima. a couple days later the elbow swelled up and they stuck me with a needle, pulling out a lot of nasty looking fluid. It was a strep B infection. They figured from leaking septic tanks along the river or cattle. Strep B is associated with raw sewage.
So, basically, I had poopy elbow.
The big danger is getting the infection deep in the elbow. There isn't a lot of blood flow in the joint so it is hard to deliver antibiotics. They said I could have lost it!
Good vibes out to Porter