they can go bad and cause bursitis. Spousal came home one evening and said his elbow felt funny. We rolled up his sleeve and he had a ping pong ball under the skin. I mean a HUGE bump. I sent him over to the pediatric MD across the street because it looked like a ER serious problem and we were about to sit down for dinner. Burst bursa was the diagnosis. We were told it can and usually heals itself but sometimes requires surgical repair. All the liquid in his elbow bursa leaked out from some trauma- all he did was lean his elbow on his desk at the office. It took a good long while but eventually resolved itself.