Magnetic Resonance Imaging of Cartilage in the Athlete: Current Techniques and Spectrum of Disease

Abstract

In the athletic population, reproducible imaging of cartilage damage is vital for treatment considerations. With appropriate pulse sequencing, magnetic resonance imaging has been shown to be an accurate noninvasive method for the evaluation of articular cartilage injuries and for evaluating postoperative changes following chondral repair. In addition, magnetic resonance imaging does not utilize ionizing radiation, has direct multiplanar capabilities, and allows high-resolution imaging of soft-tissue structures. The purposes of the present review are to update orthopaedic surgeons on the applications and techniques for magnetic resonance imaging of cartilage in the athletic population, to define the normal magnetic resonance imaging characteristics of articular cartilage, to illustrate the spectrum of articular cartilage lesions that are detectable with magnetic resonance imaging, and to review normal and abnormal magnetic resonance imaging findings following cartilage repair. After reviewing this article, the reader should (1) have a basic understanding of pulse sequences and terminology for cartilage-sensitive magnetic resonance imaging, including proton-density-weighted high-resolution fast-spin-echo sequences; (2) be able to identify normal and abnormal articular cartilage in the hip, knee, elbow, shoulder, and ankle; and (3) be able to identify normal and abnormal findings on postoperative magnetic resonance images after chondral repair techniques. An understanding of the structure of articular cartilage is crucial in order to understand the magnetic resonance imaging appearance of normal and abnormal cartilage morphology and is also the basis for the development of new imaging techniques. Articular cartilage is a viscoelastic material composed of chondrocytes (approximately 1%) embedded in an organized extracellular matrix composed primarily of water (65% to 80%), collagen, and proteoglycan. The predominant collagen is type II (95%), although smaller amounts of other collagen types (types IV, VI, IX, X, and XI) have been identified1. Collagen provides the structural framework and tensile strength of articular cartilage. Chondroitin and keratin sulfates …