I Had Sudden, Intense Bilateral Lower Leg And Ankle Cramping

i had sudden, intense bilateral lower leg and ankle cramping lasting for about 10 minutes. Cramping started in my calves, but also went to the shin area and ankles. The cramping would seize an area and after a while let up and start somewhere else. I was sleeping and it woke me up. I recently returned from walking several miles but that is my norm and it wasn't particularly warm. I don't feel dehydrated. I am on Prolia and take a calcium supplement, usually 1X/day but also a glass of milk/day. I drank a glass of OJ prior to going to bed. The intense cramping finally subsided but would come back less intense with movement of my legs. I have had leg cramping occasionally, but never this bad. Any ideas?