Human articular cartilage can degrade, losing functional quality and eventually exposing bone surfaces;​ when significantly advanced, this cartilage degradation can be diagnosed as osteoarthritis (OA). At least 12% of adults in the United States over age 60 have symptomatic knee OA [33], which limits their ability to complete activities of daily living such as walking, kneeling and squatting. Currently, knee OA can be diagnosed only when the disease is advanced and the patient is suffering from pain. There is no cure for knee OA, nor are there proven preventative therapies;​ current treatment strategies relieve the pain of OA or completely replace the knee joint.

To evaluate potential therapies and treatments, we must find a method that can identify and measure changes to cartilage prior to the onset of degradation. Magnetic resonance imaging (MRI) is a potentially powerful tool to non-invasively evaluate the progression of knee OA by mapping MR image parameters to molecular and material properties that are known to change with disease.

The goal of this dissertation was to determine MR image parameters that can be used to evaluate the progression of OA. To characterize the cartilage material properties, we created a new resource to determine the biphasic material properties of cartilage from indentation creep tests. We also determined that a viscoelastic model, an alternative to the more commonly used biphasic model, accurately represents complete indentation creep tests with the added advantage of determining an initial elastic modulus, an important material property in physiological loading conditions. Finally, we compared initial elastic modulus and cartilage macromolecules to MRI parameters, specifically T2 and T1ρ relaxation times and T1ρ dispersion. We determined that a predictive model based on T1ρ relaxation time maps, which accounts for T2 relaxation time and the effects of age, may estimate longitudinal trends in GAG content in the same person. In addition, ∆T1ρ(500-0 Hz), a simple estimate of T1ρ dispersion, has the potential for substantial clinical impact by measuring changes in cartilage initial elastic modulus and cartilage macromolecules non-invasively. This work is an important step toward developing clinical methods for evaluating cartilage functional condition and, in turn, to advance work towards preventing and treating knee OA.