Whenever I look up at the sky or try to look at the stars, my neck "clunks". I can't tell if this is a sound it makes, but I can feel the clunking sensation. What could be causing this? There's no pain but it makes me a little nervous thinking something serious is wrong.
There are several possible reasons why you might be experiencing a "clunking" sensation when you extend or hyperextend your head and neck. There could be some misalignment of the cervical spine causing one vertebra to slip over another. As you move your head, you may be subluxing (partially dislocating) the unstable vertebral segment.
In some cases, the bone is already out of place and the movement brings it back into neutral alignment. This is referred to as a reduction of the subluxation. In either case, there is likely some soft tissue damage allowing the vertebra to slide and glide in one direction more than it should.
You may benefit from some medical testing. There are some clinical exams the doctor can perform to test the integrity of the soft tissues, especially the joints and ligaments. X-rays may reveal a fracture or other bone involvement. A more advanced type of imaging may be needed such as CT scan or MRI.
Once the problem is identified, then a treatment or intervention plan can begin. Once the cervical spine is stabilized, the clunking should go away.