Professional sport keeps pace with the modern world, and puts increasing physical and mental challenges on the professional athlete. In such conditions, sports injuries are an indispensable part of everyday life for the first group, recreationists, as well as for the second, professionals. Injuries most commonly affect the locomotor system - up to 80% of all sports injuries. When we look at all the injuries that have occurred as a result of playing sports, almost half of them are some kind of knee injury. Due to its complexity and the importance of participating in movement, while withstanding heavy loads, it is often a knee-related injury. When an injury occurs, an accurate diagnosis is needed in order for the injury to be treated properly. A key role is played by modern diagnostics, which allows us to have a multiplanar view of the structures that have been injured. Here in the foreground we mean CT and MR diagnostics. MR is the diagnostic of choice for knee injuries, due to the specificity of the presentation of soft tissue structures, and we do not expose the patient to ionizing radiation. MR also gives the best insight into the structure of the anterior cruciate ligament. The anterior cruciate ligament plays an important role in the biomechanics of the knee joint. In addition to participating in the stabilization and control of joint movement, its major role is in resisting anterior tibial translation. The usual mechanism of that kind of injury is on excessive anterior tibial translation and knee valgus associated with additional tibial rotation. This paper describes the complexity of the knee anatomy and the role of the anterior cruciate ligament in it, as one of the reasons for frequent injuries, types of knee injuries and how they occur, and finally the principles of diagnosis of such injuries by magnetic resonance imaging and technical features of the examination.