Assessment of articular cartilage has become an essential part of magnetic resonance (MR) evaluation of the knee. This has occurred because of recent advances in treatment along with improved accuracy of MR image evaluation of articular cartilage. Detection of articular cartilage defects can provide an explanation for symptoms and allow identification of patients for cartilage therapy and is an important factor for predicting prognosis of patients with knee injury. This review describes the most easily implemented MR techniques for evaluation of articular cartilage and the normal and abnormal appearance of cartilage seen using these techniques. The influence of imaging findings on treatment is described.