Sport-associated knee-joint alterations are frequent. A correct and rapid differentiation between traumatic lesions, chronic degenerative changes, and adaptive processes is important with regard to therapy as well as training and competitive planning for athletes. After the case history and physical examination, X-ray images are an absolute necessity for more in-depth diagnostic procedures. Depending on the clinical symptoms, partial aspects of the knee-joint can be visualized by sonography as well as by conventional tomography and computed tomography. If, however, a comprehensive evaluation of all knee-joint structures is needed, magnetic resonance imaging of the knee-joint should be performed. As a rapid, noninvasive procedure with high diagnostic reliability for all essential knee-joint structures only magnetic resonance imaging presently fulfills the specific demands placed on a modern diagnostic procedure by doctors working in sports-medicine.