What could cause grinding under my shoulder blades when i shrug?

Need evaluation : Please see your doctor for exam and possibly an X-Ray to determine the cause. It could be benign. Hope this helps

Varies: There are a number of conditions that can contribute, most of which involve an abnormality on the under surface of the scapula. Osteochondroma a and other bony prominences can impinge on the rib cage, with motion; sometimes an increased thoracic kyphosis or a hyper mobility syndrome can contribute as well. Don't hesitate to be seen and evaluated .