Magnetic resonance (MR) imaging of articular cartilage has recently become of intense interest because of new developments in the treatment of articular cartilage injury. Recent advances in MR imaging technology has allowed the development of imaging sequences tailored to the assessment of articular cartilage. Several clinical studies have validated the accuracy and reliability of high-resolution, fat-suppressed, three-dimensional, spoiled gradient-recalled MR imaging in the assessment of articular cartilage defects of the knee. The use of other MR imaging techniques is evolving, including the use of fast spin-echo imaging and anionic contrast-enhanced T1-weighted imaging. This article describes the background and rationale to MR imaging of articular cartilage and focuses on its clinical application. Because the knee has been the focus of most research in articular cartilage imaging, the discussion in this article will be largely restricted to this joint.