I have tried to figure out what this is but its quite hard to google it and not get sidetracked.
It only hurts when I do really wide moves where I am almost at full width of arm extension and I am pulling in hard to compress something like an arete. I think I did it a few months back but I'm not sure. At the time it was easily replicable by doing pull ups. It would hurt right near the bottom of the pullup if I did wide arm pullups.
It doesn't seem to happen with the pullups anymore but on wide compression moves it happens without fail if I have to pull hard.
The pain isn't there until it suddenly comes on sharply and I have to let go.
I have attached a diagram to show where it hurts. (black circle is the pain area)
Its just in the join between the bottom of the deltoid and the top outside of the bicep.
Anyone have an idea what this might be and if there is anything I can be doing to fix it or even conclusively diagnose it?