One hundred and thirty osteoarthritic knees(65 males, 65 females) from a Chinese population were measured by computed tomography for tibial mediolateral (ML), middle anteroposterior (AP), medial anteroposterior (MAP), lateral anteroposterior (LAP) dimensions and ML/AP aspect ratio. The ML/AP aspect ratio were classified into 3 groups based on AP dimensions(<48 mm, 48–52 mm, >52 mm) to compare the morphologic differences of proximal tibia between males and females. The mean ML, AP, MAP and LAP dimensions of proximal tibia showed significant differences for sex (P < .01). We found a progressively decreased in the ML/AP aspect ratio with an increasing AP dimension, and males have larger ML/AP aspect ratio than that of females under a given AP dimension (P < .01). This indicates that under a given AP dimension prosthesis, the tibial ML dimension have the potential to be undersized in males and to overhang in females. This study may provide important reference in designing proper gender-specific tibia prosthesis with different ML/AP aspect ratio for Chinese males and females.