I had a patient with rather audible and palpable snap with neck rotation. She was concerned she had loose joints in neck. It turned out to be coming from a snapping Splenius cervicis muscle.
The splenius cervicis in the neck extends to T4:
With head rotated I could feel tight bands coming down to insert on T1-4. I massaged them out some and the snapping greatly reduced. She said her head even felt much better. The muscle must snap over the transverse processes on its way down.
any other snapping causes come to mind?