Mechanical-based treatment strategies for patellofemoral osteoarthritis (OA) have had limited success. This is likely because the magnitude of mechanical change required to improve clinical symptoms has not been quantified because, until recently, the tools required to do so were not available. The aim of this thesis was to develop and characterize MRI-based assessments of in vivo joint mechanics (three-dimensional patellar kinematics and contact areas) that can be used in studies of patellofemoral OA.

Three studies of three-dimensional patellar kinematics were carried out. Study 1 examined the effect of load on kinematic measurements. The results showed that increased load caused patellae to flex, tilt medially and translate proximally and posteriorly (p<0.05). In Study 2, the need to carry out a full kinematic assessment through the range of knee flexion was assessed. The results showed that a single, widely used measure of patellar position and orientation was an inadequate surrogate marker and a full kinematic assessment was required. In Study 3, the effect of a patellofemoral brace on kinematics was examined in patients with patellofemoral OA. The brace caused the patellae to extend, spin externally, tilt medially and translate distally, medially and posteriorly (p<0.05).

In Study 4, a method of assessing contact areas using an MRI scan of less than a minute was developed and yielded measurements with errors similar to methods employing significantly longer scans. This method can also be used in series with the kinematic method, allowing kinematics and contact areas to be assessed simultaneously.

In Study 5, a simple, patient specific, kinematics-driven multibody model to predict contact area was developed and validated. The model showed good agreement with direct measures of contact area from MRI but was sensitive to the proximity threshold value used to define contact and to the kinematic input data. This model may be useful in studies where direct measures of contact area are not possible.

The MRI-based tools for assessing patellofemoral joint mechanics in vivo characterized and validated in this thesis can potentially be used to identify the magnitude of mechanical change required to improve symptoms in patients with patellofemoral OA.