Hi Bean, My bursitis started from an overuse injury. I had not exercised for several months, then over did it. For me, one day I was fine, then the next day I couldn't walk. I've been told bursitis can come spontaneously out of the blue, but overuse is the most common cause. Also, it does seem to just go away mysteriously over time for some people. It doesn't necessarily get worse with age as arthritis often does. My hip also feels bruised and the tendons etc feel very sore. I also have better days than others. Hope this helps answer some of your questions.