Hip Effusion (Transient Synovitis) of the hip
Hip effusion as a self-limiting condition in which there is an inflammation of the inner lining (the synovium) of the capsule of the hip joint.
Physical exam and radiography are common tools for diagnosis, sonography is a great tool that increases accuracy.
Patients typically present with limping. In the hip you can see an anechoic space consistent with fluid within the joint capsule. If very large or infectious etiology is of concern an Ultrasound guided needle aspiration may be performed.
Read more:
http://ard.bmj.com/content/59/3/178.full
http://eradiology.bidmc.harvard.edu/LearningLab/…/Easter.pdf
Sonographic Tendencies 