---

- Diff Dx:
    - Intracapsular Fractures
    - Toxic Synovitis of the Hip
    - Septic Arthritis
    - Osteomyelitis
    - Legg Perthes disease in children.
- Clinical Features:
    - person suffering from a painful Hip Joint effusion is most comfortable when seated with the painful thigh lightly abducted and externally rotated at the hip joint;
    - this orientation reduces tension in synovial membrane to minimum because it maximizes encapsulation of femoral head by acetabular cavity and labrum;
- Radiographic Features:
    - most sensitive indicator of Hip Joint effusion in AP radiograph is inferolateral displacement of femoral head from acetabular cavity;
    - in children: look for medial displacement of psoas line or obturator line