IN-VITRO AND IN-VIVO MR-IMAGING OF HYALINE CARTILAGE - ZONAL ANATOMY,IMAGING PITFALLS, AND PATHOLOGICAL CONDITIONS

Hyaline cartilage plays an essential role in the maintenance of normal synovial joint function by reducing friction and distributing loads. Histologic analysis of hyaline cartilage reveals zonal variation in ce llular morphology, proteoglycan concentration, and collagen fiber size and orientation. High-resolution magnetic resonance (MR) imaging reve als an analogous laminar anatomy that is often visible on clinical ima ges obtained with proper attention to technique. In vitro and in vivo pulse sequences show three distinct laminae: a hypointense superficial lamina, a hyperintense intermediate lamina, and a heterogeneous deep lamina that consists of alternating hyperintense and hypointense bands perpendicular to the subchondral bone. Imaging pitfalls include magic angle effects, truncation artifact, partial volume effect, regional a natomic variation, chemical shift, and magnetic susceptibility effects . Pathologic conditions that affect articular cartilage include chondr omalacia patellae, osteoarthritis, and localized traumatic lesions. Al though detection of early cartilage disease remains elusive, MR imagin g can demonstrate intermediate and advanced lesions.