# Distribution of coronal plane alignment of the knee classification among Emirati patients with arthritic and healthy knees

## TL;DR

This study examines how knee alignment types are distributed among Emirati patients with arthritis and healthy knees, revealing a tendency for varus alignment in arthritic cases.

## Contribution

The study provides the first CPAK distribution data for an Emirati population, highlighting region-specific alignment patterns in arthritic knees.

## Key findings

- Arthritic knees showed a higher prevalence of CPAK I (varus alignment) compared to healthy knees.
- Arthritic knees had lower MPTA and higher LDFA, indicating more varus alignment.
- The study emphasizes the need for region-specific data in planning knee replacement surgeries.

## Abstract

Although the Coronal Plane Alignment of the Knee (CPAK) classification aids in characterising knee alignment phenotypes, it has drawbacks, such as misclassifying valgus knees as varus and allowing for significant aHKA variance within a single phenotypic. The proportions of each phenotype vary by area, despite the fact that worldwide CPAK distributions are largely stable. However, there is a lack of data from the Middle East, which restricts the system's use in planning total knee arthroplasty (TKA). Therefore, the objective of the present study was to ascertain the distribution of CPAK types among Emirati individuals with healthy knees and those with arthritis, as well as any variations in alignment traits between the two groups.

A retrospective analysis was conducted on 795 Emirati patients (366 arthritic and 429 healthy knees) using standing long‐leg radiographs. Parameters measured included lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), arithmetic hip‐knee‐ankle angle (aHKA), and joint line obliquity (JLO). Knees were classified into CPAK types based on these measurements.

The most common overall was CPAK II (neutral and apex distal) (40.4%), which was followed by CPAK I (varus and apex distal, 35.5%). In contrast to healthy knees, which were mostly CPAK II (45.5%), arthritic knees were primarily CPAK I (51.6%), suggesting a varus alignment tendency. MPTA was lower (84.75° ± 3.32 vs. 86.65° ± 2.51) and mean LDFA was greater (87.59° ± 1.86) in arthritic knees than in healthy knees (87.01° ± 1.96). With a mean aHKA of −2.85° ± 3.99, arthritis‐affected knees displayed more varus alignment than healthy knees, which had a mean aHKA of −0.37° ± 3.23.

The prevalence of varus alignment in arthritic knees and the significance of region‐specific data are highlighted by this study, which offers the first CPAK distribution data for an Emirati population. These results can be used as a basis for future longitudinal and outcome‐based studies as well as to guide customised alignment tactics in TKA.

Level IV cross sectional descriptive study without control.