Distribution of CPAK types in Chinese Han patients with osteoarthritis of the knee

Objective To analyze the distribution of the types of coronal plane alignment of the knee (CPAK) in patients with osteoarthritis of the knee in Chinese Han population. Methods Full-length films of the lower limbs were collected from 200 Han patients with osteoarthritis of the knee. The lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were measured, and parameters such as arithmetic hip-knee-ankle angle (aHKA) and joint line obliguity (JLO) were calculated. The CPAK types were determined. Results The majority of CPAK types of the knee were type Ⅰ (36.5%), followed by type Ⅳ (29.0%), type Ⅱ (12.7%), type Ⅲ (9.5%), type Ⅴ (6.4%), type Ⅶ (3.5%), type Ⅵ (2.0%), and type Ⅷ (0.4%), without type Ⅸ. Conclusions Among the CPAK types in Chinese Han population, structural inversion alignment with proximal JLO at the apex accounted for the highest percentage.