Measurement Position Influences Sex Comparisons Of Distal Femoral Cartilage Thickness With Ultrasound Imaging

Knee position during ultrasound imaging may influence cartilage measurements. Knee loading during gait varies by sex and may contribute to regional differences in cartilage features. PURPOSE: The purpose was to examine (1) the effect of measurement position and sex on femoral cartilage outcomes, and (2) the association between gait biomechanics and cartilage outcomes. METHODS: 25 males and 25 females who were matched by age and BMI participated (Females; Age = 20.6 ± 1.8 years, BMI = 23.2 ± 2.8, Males; Age = 20.6 ± 1.7 years, BMI = 23.5 ± 2.6). Ultrasound measured femoral cartilage thickness and echo-intensity (EI) at 90°, 115°, and 140° of knee flexion and was segmented into medial, central, and lateral regions. Gait outcomes included the external knee adduction and knee flexion moments. Cartilage outcomes were compared using 2(sex) x 3(position) repeated measures ANOVA. Gait and cartilage associations were assessed using stepwise regression. RESULTS: There was sex by measurement position interaction effect on medial (F2-96 = 6.11, p < 0.01, ηp2 = 0.20) and central cartilage thickness (F2-96 = 9.73, p < 0.01, ηp2 = 0.17). Males had thicker medial cartilage at 90° than 115° (p = 0.02) and 140° (p < 0.01) and at 115° than 140° (p < 0.01) and had thicker central cartilage at 90° than 115° (p = 0.01) and 140° (p < 0.01) and at 115° than 140° (p < 0.01), but females only had thicker cartilage in the central region at 90° than at 115° (p < 0.01) and 140° (p < 0.01). Cartilage was thicker at 90° compared with 140° across both sexes within all regions (p < 0.01). Males had thicker cartilage than females in all positions (p < 0.01). EI was lower at 90° than 115° (p < 0.01) and 140° (p = 0.01) in the central region and lower at 90° than 115° (p < 0.01) and 140° (p = 0.03) in the lateral region. No association was found between gait and cartilage outcomes (all p > 0.05). CONCLUSION: Imaging position has a larger effect on cartilage features in males compared with females when measured using ultrasound. To comprehensively evaluate cartilage, 3 positions may be needed for males compared to 2 positions for females. Future study designs should consider males have thicker cartilage than females and joint position influences cartilage thickness and EI. Single step gait biomechanics may be insufficient to establish associations between habitual loading and cartilage features. Natural Science and Engineering Research Council of Canada (RGPIN-2022-04804, PI: DN Pamukoff); Western University Strategic Support for NSERC (Proposal ID: 000052849; PI: DN Pamukoff); and Western University Faculty Research Development Fund (Proposal ID: 0000052443; PI: DN Pamukoff).