Teenager 13 years-old with an ankle injury from the orthopedist with diagnosis of post-traumatic arthritis is aimed to ultrasound.
Visually, the outer part of the ankle looks swollen.
At US on the anterior-medial surface visualized enlargement of anechoic space emanating from the bones of the ankle (fluid in the joint cavity?), on the lateral surface there is the increased blood flow at CFM in the soft tissues.