This is a young patient came to a casualty with a history of trauma and requested CT and discovered isolated posterior dislocation of the right hip joint and after reduction is attempted, CT is performed to assess joint congruence, evaluate for intra-articular fragments, and search for associated bone and soft-tissue injuries. Postreduction CT image shows anatomic reduction with a congruent joint. 

The presence of intra-articular gas in the setting of hip trauma may imply a prior dislocation (not provided in our case). 

The hip is a highly stable joint owing to its osseous, labral, ligamentous, and soft-tissue anatomy, usually requiring high-energy trauma to dislocate.

The most common mechanism of posterior hip dislocation is a posteriorly directed force against a flexed knee, with the hip flexed and adducted, such as from a dashboard injury in a motor vehicle crash. 

A posterior hip dislocation with either no fracture or an insignificant acetabular fracture (Levin 1, Thompson-Epstein ) is typically treated with a closed reduction only.

At an initial radiological examination in the setting of trauma, the radiologist must identify and characterize the dislocation and communicate any features that contraindicate rapid closed reduction.