Need help with a phantom symptom

Hi everyone, I have fibro, pretty severe, for 4 years. I need help with a symptom that I've had a few times of the past 6-8 months. I don't know when it started excactly, but it is a sharp stabbing pain in one of my shins. It in the leg I had a knee replacement 2 years ago so I thought, blood clot.
It is one of the worst pains I've eve felt and I have dealt with a lot of different pains. This comes on wothout warning, lasts for 10 seconds to a minute, then it's gone. My knee doctor said it wouldn't be a blood clot, It hit in the middle of the night last night and I had to go to the ER. ER did ultrasound, no blood clot, probably nerve pain? Nothing to do about it.
I don't go to the ER, not that kind of person. That's how bad it was. It just happened again tonight 3 times. It makes me scream. Has any Fibro brothers or sisters have this happen to any part of your body?
Thanks everyone, Kim