Imaging biopsy composition at ACL reconstruction.

Purpose: Early-stage osteoarthritis (OA) includes glycosaminoglycan (GAG) loss and collagen disruption that cannot be seen on morphological magnetic resonance imaging (MRI). T1ρ MRI is a measurement that probes the low-frequency rate of exchange between protons of free water and those from water associated with macromolecules in the cartilage's extracellular matrix. While it has been hypothesized that increased water mobility resulting from early osteoarthritic changes cause elevated T1ρ MRI values, there remain several unknown mechanisms influencing T1ρ measurements in cartilage.