I love this topic !
I have always described myself as an “ischial bursa sceptic” !
I have never been convinced it even exists.
My scepticism is based on scanning hundreds, if not thousands of them and never being convinced there is a true bursa appearance and then it is reinforced by guiding hundreds / or thousands of injections into the area.
When you inject the tissue superficial to the hamstring origin and deep to G-max (the so called ischial bursa) it does not behave like a bursa at all. There is a potential space there and all of the liquid injected runs down the lateral side of the hamstring origin and collects in a sump with he floor being quadrates femurs, the roof being G-max and the sciatic nerve gets a free drink of steroid and local anaesthetic !!!
So, no I AM NOT BUYING THE BURSA STORY.
I have seen increased flow and inflammatory change in this potential space area and I am happy that you can get a peritonitis of the hamstring origin which is usually associates with hamstring origin tendinosis (just like all bursitis, fat pad inflammation etc is associated with an underlying degenerate tendinosis or enthesopathy). You could also convince me there is a potential for an adventitial bursitis in this area similar to the situation with intersection syndrome of the wrist ( APL / EPB over ECRL / ECRB )
Steve