Compositional MR imaging of cartilage and joint mechanics

MRI-based compositional measurements of cartilage have been developed to characterize the biochemical composition of articular cartilage and the menisci, allowing the assessment of cartilage quality before cartilage loss has occurred and changes are still potentially reversible. They have also been used to investigate the complex relationship between biomechanics and cartilage health. This review focuses on cartilage T_1rho and T₂ cartilage compositional measurements as these techniques have been most frequently used in studies involving joint biomechanics. Recent clinical and in vitro studies are covered, including those investigating the relationship of cartilage composition with physical activity, gait, muscle strength, and biomechanical loading of specimens. These studies clearly illustrate the impact of physical activity on cartilage, how gait alterations after anterior cruciate ligament reconstruction may lead to early degenerative disease, and the complex interplay between muscle strength, gait, and cartilage composition. In vitro work also demonstrates how indentation stiffness correlates with cartilage composition. The review further consolidates the important role of cartilage compositional imaging in understanding the biomechanics and pathophysiology of degenerative joint disease.