2025 · Journal of Bone and Joint Surgery American Volume
Do CPAK Distribution, aHKA, and JLO Differ with OA Severity?
As KL increased, the most frequent CPAK type shifted from II to I (P < 0.05). LDFA and JLCA increased; HKAA, MPTA and aHKA decreased beyond KL 2.
Research question and design
Enlarge FigureCPAK, aHKA and JLO distributions were compared by KL grade in 17,365 knees.
Journal of Bone and Joint Surgery American Volume (2025). DOI: 10.2106/JBJS.24.00316 · Original explanatory chart based on reported data
The research question
Participants and Methods
Main Findings
Implications for clinical and surgical practice
Limitations
Let's put it briefly.
Which clinical question does this address?
This cautions against assuming that CPAK in an arthritic knee directly represents its original anatomical alignment when planning reconstruction.
Keywords
- Osteoarthritis, Knee
- Knee Joint
- Retrospective Studies
- Cross-Sectional Studies
- Radiography
- Severity of Illness Index
- TKA
- CPAK
Abstract · Original text
Sung Eun Kim, Samuel MacDessi, Daeseok Song, Joong Il Kim, Byung Sun Choi, Hyuk-Soo Han, Du Hyun Ro. Coronal Plane Alignment of the Knee (CPAK) Type Shifts Toward Constitutional Varus with Increasing Kellgren and Lawrence Grade: A Radiographic Analysis of 17,365 Knees. The Journal of bone and joint surgery. American volume. 2025;107(3):297-303. doi:10.2106/JBJS.24.00316.
BACKGROUND
Studies investigating constitutional alignment across various grades of osteoarthritis (OA) are limited. This study explored the distribution of Coronal Plane Alignment of the Knee (CPAK) types and associated radiographic parameters with increasing OA severity.
METHODS
In this retrospective cross-sectional study, 17,365 knees were analyzed using deep learning software for radiographic measurements. Knees were categorized on the basis of the Kellgren and Lawrence (KL) grade and CPAK type. Radiographic measurements were the hip-knee-ankle angle (HKAA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), arithmetic HKAA (aHKA), joint line obliquity (JLO), and joint line convergence angle (JLCA). Age-stratified analysis was performed to differentiate the impact of age on OA severity.
RESULTS
A shift in the most common CPAK type from II to I was found with increasing KL grade (p < 0.05). Furthermore, there was a corresponding increase in LDFA and JLCA with increasing KL grade, while HKAA, MPTA, and aHKA decreased after KL grade 2. Age exhibited limited association with LDFA and MPTA, suggesting that OA severity is the dominant factor related to the CPAK distribution.
CONCLUSIONS
The study found a shift in CPAK type with worsening OA. It is possible that constitutional varus types are more susceptible to OA, or that their increased OA prevalence is related to anatomical changes. This analysis offers new insights into alterations in CPAK type that occur with OA and underscores the importance of understanding pre-arthritic anatomy when performing joint reconstruction.
LEVEL OF EVIDENCE
Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.
Copyright © 2024 The Author(s). Published by The Journal of Bone and Joint Surgery, Incorporated.
The original paper.
Coronal Plane Alignment of the Knee (CPAK) Type Shifts Toward Constitutional Varus with Increasing Kellgren and Lawrence Grade: A Radiographic Analysis of 17,365 Knees
Sung Eun Kim, Samuel MacDessi, Daeseok Song, Joong Il Kim, Byung Sun Choi, Hyuk-Soo Han, Du Hyun Ro
Journal of Bone and Joint Surgery American Volume · 2025 · online 2024