Joint-adjacent Adipose Tissue by MRI is Associated With Prevalence and Progression of Knee Degenerative Changes: Data from the Osteoarthritis Initiative

Background: Adipose tissue has recently gained interest as an independent imaging biomarker for osteoarthritis. Purpose: To explore 1) cross-sectional associations between local subcutaneous fat (SCF) thickness at the knee and the extent of degenerative changes in overweight and obese individuals and 2) associations between local fat distribution and progression of osteoarthritis over 4 years. Study Type: Retrospective cohort study. Population: 338 obese and overweight participants from the Osteoarthritis Initiative cohort without radiographic evidence of osteoarthritis. Field Strength: 3T: 3D-FLASH-WE; 3D-DESS-WE; T1w-SE; MSME. Assessment: Baseline SCF thickness was measured in standardized locations medial, lateral and anterior to the knee and the average joint-adjacent SCF (ajSCF) was calculated. Right thigh SCF cross-sectional area was assessed. Quantitative cartilage T₂ relaxation times and semi-quantitative whole organ MRI scores (WORMS) were obtained at baseline and 4-year follow-up. WORMS_sum was calculated as sum of cartilage, bone marrow edema, subchondral cyst, and meniscal scores. Statistical Tests: Associations of SCF measures with baseline, and 4-year change in T₂ and WORMS were analyzed using regression models. SCF measurements were standardized using the equation (Formula presented.). Analyses were adjusted for age, sex, physical activity, and BMI. Results: Cross-sectionally, significant associations between lateral SCF, lateral compartment WORMS and T₂ were found ((Formula presented.), [95% CI]: 0.53, [0.12–0.95], P < 0.05; ΔT₂: 0.50, [0.02–0.98], P < 0.05). Moreover, greater lateral SCF was associated with faster progression of lateral WORMS_sum gradings (OR = 1.50, [1.05–2.15], P < 0.05). No significant positive associations were found for thigh SCF and WORMS_sum (P = 0.44) or T₂ measurements (medial: P = 0.15, lateral: 0.39, patellar: P = 0.75). Data Conclusion: Joint-adjacent SCF thickness was associated with imaging parameters of knee osteoarthritis, both cross-sectionally and longitudinally, while thigh SCF was not, suggesting a spatial association of SCF and knee osteoarthritis. Based on these findings, joint-adjacent SCF may play a role in the development and progression of knee osteoarthritis. Level of Evidence: 4. Technical Efficacy: Stage 5.