Hi Dave,
Yes, I agree the collagen looks hypo echoic in long axis and hence I don’t trust long axis imaging and depend heavily on short axis assessment.
Short axis is reproducible and reliable.
I also agree there is usually pain with sonopalpation of the ischial tuberosity if there is enthesopathy or tendinosis present. A lack of pain and a hypo echoic , swollen tendon would indicate old disease that is now asymptomatic.
As far as a provocative manoeuvre goes, I would need to consult a sports and exercise physican to find out what clinical test is most reliable.
FAI is a different topic.
You can see early OA changes on ultrasound and paralabral cysts from the early labral degeneration / tears. These are clues to the presence of FAI.
With Cam type FAI you may see that the femoral head / neck contour is not as you would expect and the femoral head continues to bulge down into the expected neck area. You lose the typical “slippery slide” contour from the head down to the neck. You especially see this just lateral to the midline of the femoral neck and you may see an associated bony defect in the lateral margin of the acetabular rim.
I can not see pincer type FAI on ultrasound, just the OA and labral changes associated with it.
In the end a plain radiograph series is always essential.
Steve