Sex-specific differences in coronal knee alignment and CPAK distribution in an Austrian population

To describe coronal plane alignment patterns and Coronal Plane Alignment of the Knee (CPAK) type distribution in an Austrian population, and to evaluate associations with sex, age, and body mass index (BMI). In this retrospective study, 400 knees with complete demographic and radiographic data from standardized long-leg standing radiographs were analyzed. Mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), arithmetic hip–knee–ankle angle (aHKA), and joint line obliquity (JLO) were measured, and CPAK types were assigned. Statistical analysis included Shapiro–Wilk tests, Welch’s t-test, Chi-square, Fisher’s exact, binary logistic regression, linear regression, and multinomial logistic regression, with significance set at p < 0.05. The cohort comprised 266 females (68%) and 134 males (32%), with a mean age of 68.3 years and mean BMI of 30.4 kg/m². Mean aHKA was − 0.03°, with males showing greater varus alignment than females (− 1.40° vs. +0.67°, p = 0.00011). The most frequent CPAK types were I and II (each 21.8%), followed by VI (15.5%), III (15.3%), V (12.5%), and IV (11.3%). CPAK distribution differed by sex (p = 0.023) but not by age group. Male sex increased the odds of varus alignment (OR ≈ 2.27, p < 0.001) and reduced the odds of valgus alignment (OR ≈ 0.40, p < 0.001). BMI was associated with varus alignment in males (p = 0.033) but not in females. In this Austrian cohort, males exhibited greater varus alignment and a distinct CPAK distribution compared to females, while age showed no effect on alignment patterns. BMI predicted varus alignment only in males. These findings provide valuable region-specific CPAK reference data for Austria, supporting individualized alignment strategies in total knee arthroplasty.