What Causes Electrical Pulse In Ankle?

I have a reoccurring pulse in my left ankle, it feels like a mild electrical pulse that lasts for seconds. It started a few months ago & was infrequent, but not its every other day. It only lasts seconds, but it is a strange feeling. I have had no surgeries & I have not injured this ankle. What could This be? Do I need an ultra sound?
Thanks