The abnormalities demonstrated on recent pelvic x-ray are confirmed. There is an avulsion fracture of the straight head rectus femoris from the anterior inferior iliac spine (AIIS) with a gap of perhaps 6mm as well as the reflected head (nicely seen on the sagittal projection as a Y-shape). Soft tissue swelling with fluid in the intervening gap. The tendon remains attached to these separated bony fragments. This would account the two fragments of bone seen on the plain radiograph.
No other specific bone or joint abnormality. No intrinsic hip joint pathology in particular no joint effusion.
Conclusion: The patient has definite avulsion of the straight head of rectus femoris from the anterior inferior iliac spine with a gap of around 6mm. There is also avulsion of the 2nd rectus femoris head (posterior or reflected) from the rim of the acetabulum. This would account for the two bone fragments seen on the plain radiographs. No other intrinsic hip joint abnormality.