Coronal lower limb alignment in normal knees--A radiographic analysis of 797 normal knee subjects

Background: This study aimed to resolve uncertainty regarding sex differences in alignment changes with age.

Methods: We measured various parameters of weight-bearing long leg radiographs of 797 legs without osteoarthritic changes, which were classified according to sex and age (young [15-39 years], middle-aged [40-54 years], aged [55-69 years], and elderly [≥70 years]), and performed morphological analysis of the lower extremities. The mean measurements in each group were calculated and compared among the groups.

Results: In the young and middle-aged populations, the femorotibial angle was significantly more varus in male than in female participants (p<0.001). In addition, medial femoral bowing was seen both in male and female participants, but it was more significant in male participants (p<0.005). This was due to greater femoral condylar orientation (p<0.01) and tibial plateau inclination (p<0.01) in male participants compared to female participants with nearly identical joint space narrowing. In aged and elderly populations, on the contrary, lateral femoral bowing was seen in both male and female participants, and there were no differences in any measured values, including the femorotibial angle, between male and female participants.

Conclusions: In relatively young Japanese individuals, male participants' femorotibial angles were more varus and had more medial femoral bowing than female participants, while there was no difference in any measured values between male and female participants in older adults by a radiographic analysis on the alignment of the lower extremities.

Level of evidence: Level 2.