Purpose: To investigate the association of the presence and severity of diabetes mellitus (DM) with articular cartilage composition, using magnetic resonance imaging (MRI)-based T 2 relaxation time measurements, and structural knee abnormalities. Materials and Methods: In the Osteoarthritis Initiative 208, participants with DM (age 63.0 6 8.9 years; 111 females) and risk factors for osteoarthritis (OA) or mild radiographic tibiofemoral OA (Kellgren-Lawrence [KL] grade 2) were identified and group-matched with 208 controls without DM (age 63.3 6 9.1 years; 111 females). Subjects with diabetes-related renal or ophthalmological complications or insulin treatment at baseline (n 5 50) were defined as severe DM. 3T MR images of the right knee were assessed for articular cartilage T 2 , including texture and laminar analyses derived from the patella, medial, and lateral femur and tibia and for structural abnormalities using the modified whole-organ magnetic resonance imaging score (WORMS). Clustered linear regression analyses were used to assess associations of DM with MRI findings. Results: DM subjects had significantly higher cartilage T 2 in the patella (mean difference 0.92 msec [95% confidence interval (CI) 0.79, 1.06]; P 5 0.001) and medial femur (mean difference 0.36 msec [95% CI 0.27, 0.81]; P 5 0.006) compared to controls. Averaged over all compartments, DM subjects showed significantly higher texture parameters (variance, P 5 0.001; contrast, P 5 0.002; entropy, P < 0.001). Subjects with severe DM additionally showed higher T 2 in the medial tibial deep and superficial layers (P 5 0.011 and P 5 0.041) compared to controls. No significant differences in cartilage, meniscus, and overall WORMS were found between the groups (P > 0.05). Conclusion: In comparison to nondiabetic controls, cartilage in DM subjects showed higher and more heterogeneous cartilage T 2 values, indicating increased articular cartilage degeneration. This affected even more compartments in subjects with severe DM. Level of Evidence: 2 Technical Efficacy: 5