The knee is one of the most injured joints in the human body, accounting for an estimated 1.3 million visits to the emergency department annually in the USA and approximately 6% of all acute injuries in a prospective European study. Radiographs have low yield for the diagnosis of clinically relevant fractures and are often negative despite significant internal derangement of the knee. Computed tomography (CT) allows for a fast and accurate examination of patients for whom there is a high clinical suspicion of a radiographically occult fracture and to determine the intra-articular extent of the injury for presurgical planning. CT angiography is indicated in cases of supracondylar fracture or knee dislocation, even if spontaneously reduced, as there is a higher incidence of popliteal artery injury. Soft tissue injuries and internal derangements of the knee are best evaluated on MRI given its high soft tissue spatial resolution.