Interesting case,
It indeed could be a large iliopsoas bursa in a slightly more medial location to what I normally expect.
I can’t think of anything else that would be so large and cystic in that location,
It is close to the femoral ring also,
The patient is very young so it is hard to believe the hip joint has significant arthritis or degenerative changes.
Big iliopsoas bursae like this one are usually associated with a hip degenerative condition and they communicate with the hip joint.
You can get a pure bursitis and perhaps that is the case here after the exercise in Melbourne.
I also wonder about rheumatoid when I see a big bursa this size,
It will be a good one to follow up,
An MRI would be interesting.
Nice one,
Steve.