Traumatic lipohemobursa of the infrapatellar bursa.

Displaced fractures allow spillage of bone marrow and blood into the surrounding soft tissues. When the fracture is intra-articular, the spilled marrow contents may be contained by the associated joint capsule, resulting in a lipohemarthrosis. This is sometimes visible as a fat-fluid level on imaging. At the knee, the characteristic appearance of lipohemarthrosis within the suprapatellar recess signifies the presence of an intra-articular fracture that may otherwise not be radiographically apparent. We present a case in which an extra-articular proximal tibia fracture allowed spillage of marrow contents into the deep infrapatellar bursa, resulting in a lipohemobursa. The radiologic appearance mirrors the classic appearance of lipohemarthrosis with a fat-fluid level.