Suggest Remedy For Large Fluid Filled Blisters On The Back Of Legs

I woke up yesterday morning with two large fluid filled blisters on the back of my leg, either side of my knee joint. This morning a few more blisters have developed around the surrounding area of the original blisters (now popped). Any ideas what they may be, and why so isolated? I am a very active 46 year old female, no allergies, no medical conditions and not on any medication.