Purpose: (1) To identify the relationship between anteromedial notch ridging, a recently identified non-contact anterior cruciate ligament injury risk factor, and patient demographics in a general population. (2) To characterize the symmetry of the femoral notch between knees.
Methods: The femoral notches of 170 non-arthritic archival skeletal specimens devoid of soft-tissue attachments (n = 79 females, 90 males, 34.3 ± 15.7 years) were measured for notch width, ridge thickness, and outlet stenosis due to ridging. Measurements were compared by race and sex by ANOVA, and Pearson correlations were calculated for all continuous measures.
Results: Percent stenosis was associated with increasing age (p < 0.001, r = 0.40). Ridge thickness was similar among men (2.7 ± 1.6 mm) and women (3.1 ± 1.5; n.s.). Women had narrower notches (16.0 ± 2.1 mm) and higher percent stenosis (19.6 ± 9.9 %) than men (p ≤ 0.001; men 19.3 ± 2.4 mm; 14.4 ± 8.7 %). African American men have narrower notches than Caucasian men (20.4 ± 2.5 vs. 18.7 ± 2.3 mm, respectively; p = 0.002) with no difference between women of both races (16.2 ± 2.5 vs. 15.8 ± 1.6 mm, respectively; n.s.). A positive association was observed between height and notch width among men only (18+ years men p = 0.004, r = 0.33; women n.s., r = 0.21). Finally, both total notch width and ridge thickness are symmetric between knees (p < 0.001; r = 0.98 and 0.93, respectively).
Conclusions: Women have narrower femoral notches overall and also exhibit greater percent notch stenosis due to anteromedial ridging than men. Anteromedial ridging increases with age, suggesting progressive formation over time. Finally, both notch width and ridge thickness are highly symmetric between knees.