Study on the Distribution Characteristics of Coronal Plane Alignment of the Knee （CPAK） Classification in Patients with Knee Osteoarthritis and Healthy Individuals in Yunnan，China

Jia CHENG; Anli ZHOU; Zhihang SUN; Hao TANG; Wenjin LI; Ning LU

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Jia CHENG, Anli ZHOU, Zhihang SUN, Hao TANG, Wenjin LI, Ning LU. Study on the Distribution Characteristics of Coronal Plane Alignment of the Knee （CPAK） Classification in Patients with Knee Osteoarthritis and Healthy Individuals in Yunnan，China[J]. Journal of Kunming Medical University.

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Study on the Distribution Characteristics of Coronal Plane Alignment of the Knee （CPAK） Classification in Patients with Knee Osteoarthritis and Healthy Individuals in Yunnan，China

Department of Orthopedics ，The Second Affiliated Hospital of Kunming Medical University，Kunming Yunnan 650101，China

Received Date: 2026-01-18
Available Online: 2026-05-24

Abstract

Abstract

Objective To investigate the distribution characteristics of the Coronal Plane Alignment of the Knee （CPAK） classification in patients with knee osteoarthritis （KOA） and healthy individuals in Yunnan, China . Methods A total of 243 KOA patients （263 knees） from Yunnan were enrolled as the KOA group, and 69 healthy young adults （138 knees） as the healthy group. Based on parameters including the hip-knee-ankle angle （HKA）, lateral distal femoral angle （LDFA）, and medial proximal tibial angle （MPTA）, the arithmetic hip-knee-ankle angle （aHKA） and joint line obliquity （JLO） were calculated to determine the CPAK classification. Differences in classification distribution among subgroups were compared. Results The healthy group was predominantly composed of CPAK type 2 （37.7%）, type 1 （23.9%）, and type 3 （17.4%）, with no cases of types 7, 8, or 9. The KOA group was mainly composed of CPAK type 1 （53.2%） and type 4 （22.1%）, with no cases of type 8 and only one case of type 9. After adjusting for age, BMI, and gender, no statistically significant differences were found in any CPAK type between the two groups （P > 0.05）. In the healthy group, there were no significant differences in CPAK distribution between genders （P > 0.05）, and bilateral consistency of CPAK classification was only 39.1%. In the KOA group, no significant differences in CPAK types were observed among subgroups stratified by gender, age （<65 years vs. ≥65 years）, or BMI （<25 kg/m² vs. ≥25 kg/m²）（P > 0.05）, with type 1 and type 4 being predominant in all subgroups. The proportion of constitutional varus in the KOA group （77.6%） was significantly higher than that in the healthy group （32.6%）. Compared with the healthy group, the KOA group had lower MPTA, higher LDFA, and higher aHKA （P < 0.001）. Conclusions The most common distributions in Yunnan healthy and osteoarthritic populations were types 2 and 1, respectively. Gender, BMI, and age do not affect the distribution of CPAK types. The contralateral limb should not be used as a reliable reference for coronal alignment planning in total knee arthroplasty.
- Coronal plane alignment of the knee,
- Osteoarthritis,
- Constitutional alignment,
- Total knee arthroplasty

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References(41)

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