Hyaline cartilage lining the surfaces of diarthrodial joints is an important construct for transmission of load and to reduce friction between the bones. Normal wear and tear accounts for about 3-5 percent knee cartilage loss ever year in otherwise healthy people after the age of 30 years. Several conditions and diseases lead to premature cartilage degeneration. Standardized description of cartilage loss, detailed evaluation of the joint health and determining the underlying etiology of cartilage loss are important for effective reporting, multidisciplinary communications and patient management. In this article, the authors discuss normal and abnormal imaging appearances of the hyaline cartilage of knee with focus on using controlled terminology and MRI classifications. The reader will benefit and learn key MR imaging features of a spectrum of common and uncommon conditions and diseases affecting the knee cartilage, such as trauma, secondary injury associated with meniscus and ligament injury related instability, arthritis, ischemia, idiopathic, and hereditary conditions including Matrix metalloproteinase-2 (MMP-2) mutations and mucopolysaccharidosis type IX disease with illustrative case examples.Copyright © 2020 Elsevier B.V. All rights reserved.