What is the most likely cause of shoulder pain with a sensation of grating during overhead movement?

The sensation of grating, often described as crepitus, during overhead movement of the shoulder is commonly associated with rotator cuff tendinitis. This condition arises when the rotator cuff tendons become inflamed, often due to repetitive overhead activities or aging. The inflammation can lead to thickening of the tendons, and as the shoulder is moved, particularly in overhead positions, the inflamed tendon may rub against the bony structures of the shoulder, creating that sensation of grating.

In contrast, while shoulder impingement syndrome could also involve symptoms during overhead motion, it is more specifically characterized by pain during certain movements rather than a distinct grating sensation. Frozen shoulder is primarily associated with stiffness and a limited range of motion, rather than a grating feeling. An acromioclavicular joint injury might cause pain in the shoulder area but typically wouldn’t present with a grating sensation during overhead activities.

Therefore, the combination of pain with a distinct grating sensation during overhead movement points most clearly towards rotator cuff tendinitis as the underlying cause.