Sex-related differences in femorotibial cartilage thickness: a matched pair analysis

Women are more frequently affected by knee osteoarthritis (OA) than men. Differences in knee cartilage thickness have been proposed as an explanation, but it remains unclear whether these differences reflect true sex-specific variation or differences in body size. Clarifying this may improve our understanding of sex-specific mechanisms in knee OA development. The objective of this study was to quantify and visualize cartilage thickness differences between men and women without radiographic knee OA matched for age and body size. Subjects without radiographic signs of knee OA were selected from the Osteoarthritis Initiative (OAI). Male-female pairs were matched (1:1) for age (±5 years), BMI (±2 kg/m²), and height (±1 cm). Cartilage thickness was assessed from 3 T MRI data using compartmental analysis and whole-joint 3D cartilage surface mapping (CaSM). Paired t-tests (for compartmental analysis) and statistical parametric mapping (F-tests for CaSM) were applied to compare sexes. 126 Subjects were included (age 57.7±8.4 years; BMI 26.4±3.7 kg/m²; height 169.5±5.3 cm). Cartilage was thicker in men than in women in both the lateral (0.41±0.56 mm) and medial (0.38±0.62 mm) femorotibial compartment (both p<0.001). CaSM identified five femorotibial regions with significant sex differences (p<0.05), largest in the trochlea (16.1%; men: 2.83±0.46 mm; women: 2.44±0.36 mm). Even when matched for age and body size, men display thicker femorotibial cartilage than women, with the greatest disparity in the trochlea. These inherent sex-related cartilage thickness differences may contribute to the higher prevalence of knee OA in women and highlight the importance of considering sex in OA research and treatment strategies. • Men have thicker femorotibial cartilage than women matched for age, BMI, and height • Sex differences were present in both medial and lateral femorotibial compartments • 3D cartilage surface mapping identified five regions with sex-related differences • Largest sex-related cartilage thickness disparity observed in the trochlea region