I had it with DD and I put it down to her joints 'cracking', just like ors do sometimes. When she was born and even now, she has a knee that cracks rather regularly!
:yeahthat:
I had exactly the same thing with DD2, DH & I could often hear clicks whilst she was inside me. When she was born, her little joints often clicked... it used to worry DH as he hated the sound of it.