Knee osteoarthritis (OA) is caused by cartilage degeneration which has been shown to be accompanied by the changes in adjacent subchondral bone. Simultaneous PET-MRI enables investigating the biomarkers of cartilage degeneration in OA with MRI (i.e. T1ρ, T2 and Gadolinium uptake) as well as biomarkers of bone remodeling in OA with PET (uptake of NaF tracer in bone) at the same time. PET-MRI also allows for probing the associations between different bone and cartilage markers. Voxel-wise assessment of these associations provides insight into the local correlations between different OA markers and yields comprehensive assessment of knee OA progression.