Popping sound in knee while riding today

This morning I was on my morning "go get some doughnuts ride" and while climbing a grade (maybe 5% or so) I was pushing pretty hard to maintain momentum, I heard and felt a rapid and multiple popping noise in my right knee.  Imagine the sound made when you step on a sheet of bubble wrap.  It did not hurt and still does not hurt however it did surprise me.  Is this normal?