Osteoarthritis (OA) is the most common form of arthritis, and affects approximately 1.8 million people in Australia, with prevalence rates expected to increase due to our ageing population and obesity crisis. The knee joint is most commonly affected by OA of all the weight-bearing joint. Studies involving people with knee OA have focused on the tibiofemoral joint, with little acknowledgement on the patellofemoral joint. The aim of this thesis was to investigate the prevalence, clinical features, treatment strategies and prognosis of patellofemoral OA. Five studies were conducted in order to explore this aim. Firstly, a systematic review and meta-analysis determined the prevalence of patellofemoral osteoarthritis, by pooling data from published studies that reported radiographically confirmed compartmental patterns of knee osteoarthritis. Following, a reliability and validity study validated an assessment tool for patellofemoral OA using magnetic resonance imaging (MRI). Prior to this thesis, there were no tools to specifically assess OA features in the patellofemoral joint. Using the assessment tools assessed in this study, a cross-sectional study using the data from the Long-Term Evaluation of Glucosamine Supplements (LEGS) evaluated whether pain, activity limitations and quality of life differ between people with different compartmental distributions of MRI-based OA structural features in the knee. People with MRI-defined patellofemoral OA were identified, and used to investigate the effectiveness of glucosamine and chondroitin supplements on MRI-based OA features in the patellofemoral joint in a randomised placebo-controlled study design. Finally, this cohort was followed up two years after the study period for a fifth study that investigated the prognosis of MRI-based patellofemoral osteoarthritis using this cohort of people with baseline knee pain. The results from this thesis provided new insights to the literature on patellofemoral OA as well as knee OA.