Post-traumatic knee lipohemarthrosis: Temporal evolution with progressive separation of the three layers of the joint effusion by Ultrasonography and Computed Tomography

We report a case of intra-articular fracture of the knee joint showing at a first Ultrasonographic (US) evaluation two layers within joint effusion: a superior hyperechoic layer with oval hypoechoic structures interpreted as blood trapped in the layer of fat and an inferior hypo-anechoic layer of blood. After joint immobilization three layers were shown by Computed Tomography (CT) scan (double fluid–fluid level): a superior hypodense layer of fat, an intermediate water-density layer of serum and an inferior hyperdense layer of red blood cells.