Associations between Weight Change, Knee Subcutaneous Fat and Cartilage Thickness in Overweight and Obese Individuals: 4-Year Data from the Osteoarthritis Initiative.

OBJECTIVE: To assess (i) the impact of changes in body weight on changes in joint-adjacent subcutaneous fat (SCF) and cartilage thickness over 4-years and (ii) the relation between changes in joint-adjacent SCF and knee cartilage thickness.

DESIGN: Individuals from the Osteoarthritis Initiative (total=399) with >10% weight gain (n=100) and >10% weight loss (n=100) over 4 years were compared to a matched control cohort with less than 3% change in weight (n=199). 3.0T MRI of the right knee was performed at baseline and after 4 years to quantify joint-adjacent SCF and cartilage thickness. Linear regression models were used to evaluate the associations between the (i) weight change group and 4-year changes in both knee SCF and cartilage thickness, and (ii) 4-year changes in knee SCF and in cartilage thickness. Analyses were adjusted for age, sex, baseline BMI, tibial diameter (and weight change group in analysis (ii)).

RESULTS: Individuals who lost weight over 4-years had significantly less joint-adjacent SCF (beta range, medial/lateral joint sides: 2.2mm to 4.2mm, p<0.001) than controls; individuals who gained weight had significantly greater joint-adjacent SCF than controls (beta range: -1.4mm- -3.9mm, p<0.001). No statistically significant associations were found between weight change and cartilage thickness change. However, increases in joint-adjacent SCF over 4-years were significantly associated with decreases in cartilage thickness (p=0.04).

CONCLUSIONS: Weight change was associated with joint-adjacent SCF, but not with change in cartilage thickness. However, 4-year increases in joint-adjacent SCF were associated with decreases in cartilage thickness independent of baseline BMI and weight change group.