Spinoglenoid Cyst of the Shoulder

In order for muscles to work properly, the nerves that innervate (supply) them must also function appropriately. In some injuries, fluid may escape from the shoulder joint and form a cyst. Depending on the location of the cyst, nerves that pass nearby may become compressed in a smaller space due to the pressure from the cyst. When this occurs, nerve function decreases and the muscle may atrophy (waste away) and weaken.

Some patients may develop a spinoglenoid cyst from a superior labral or capsular injury to the shoulder. The cyst can grow below the spine of the scapula (which runs along the back of the shoulder) and above the glenoid (shoulder socket) in a location called the spinoglenoid notch. The suprascapular nerve runs through this area, and the resulting pressure causes atrophy in the infraspinatus muscle, which is one of the rotator cuff muscles. As a result of this cyst, the patient may experience pain and shoulder dysfunction as the infraspinatus weakens and is unable to perform its typical functions.