Well, not grease, but rather medicine:
About two weeks ago, as my hand was healing up, the elbow on my other arm began to hurt. I didn't recall hitting it or anything. My best guess was that it was some delayed pain from the sidewalk fall which broke my hand. However, I did NOT mention this to the doctor. I thought it was just a sprain and would heal on its own. I just couldn't face the thought of having a cast on my hand AND my elbow.
But where my hand has been healing just fine, this elbow hasn't gotten any better, and the swelling was getting larger and it felt very warm to the touch. Finally I went to the doctor today and showed him the elbow. He immediately said that it wasn't the bone nor a sprain, but instead I had an infection! Just like when I thought I had a sprain, I have no idea what caused it. So I was given an antibiotic shot, a 3-day course of oral antibiotics, and told to check back tomorrow. He said something about aspirating the infection with a needle if it didn't get better soon!