I thought I had a shoulder problem. The doctor says it's the AC joint. My shoulder still hurts. What's the difference between these two problems?

The true shoulder joint is where the head of the upper arm bone (humerus) inserts into a shallow cup in the shoulder blade. The cup is called the glenoid cavity. It's a ball and socket joint.

Just above the true shoulder joint is a bony projection coming around from the back of the shoulder blade. This piece of bone is called the acromion. The end of the acromion meets the collarbone to form a shelf over the shoulder.

Pain from any of the structures around or above the shoulder joint can cause pain that seems like it's coming from the joint. A careful exam by your doctor can pinpoint the exact cause. This is helpful information so the right problem is treated.