KSSTA - 2026-05-15 - Journal Article
Severity-dependent shift in knee osteoarthritis toward a dominant varus-flexion alignment phenotype on weight-bearing 3D imaging.
Liang Z, He J, Rong F, Li H, Zhang Y, Chen Z, Zhang Y, Yu X, Zhang M, Zheng H, Ye C, Sun X, Xia C, Li Z, Tang J
Topics
Key Takeaway
Weight-bearing 3D spatial HKA alignment correlates more strongly with joint space narrowing (r=0.52–0.61) and WOMAC scores (r=0.45–0.56) than conventional 2D HKA, with 89.1% of KL Grade 4 knees exhibiting a varus-flexion phenotype.
Summary Depth
Choose how much analysis to show on this article page.
Summary
This prospective study used weight-bearing CBCT to measure 3D spatial HKA angles in 296 knees across KL Grades 1–4, comparing multiplanar alignment to conventional 2D radiographic HKA and correlating both with joint space narrowing and WOMAC scores. 3D spatial HKA demonstrated superior correlation with structural and symptomatic outcomes versus 2D measures. Varus-flexion alignment prevalence increased from near-neutral in mild OA to 67.2% in KL Grade 3 and 89.1% in KL Grade 4, with finite element modeling confirming increased medial and posterior cartilage stress in this phenotype.
Key Limitation
The cross-sectional design cannot establish whether varus-flexion malalignment is a cause or consequence of advanced cartilage loss, limiting causal inference and its direct application to alignment correction targets in TKA.
Original Abstract
PURPOSE
To determine whether weight-bearing three-dimensional (3D) spatial hip-knee-ankle (HKA) alignment exhibits severity-dependent changes across knee osteoarthritis (KOA) stages, whether it is more strongly associated with joint structure and symptoms than conventional two-dimensional (2D) HKA alignment, and whether these 3D alignment patterns correspond to distinct cartilage stress distributions.
METHODS
This prospective study enroled 151 patients (296 knees) with radiographic KOA (Kellgren-Lawrence [KL] Grades 1-4). Spatial HKA angles, defined as 3D mechanical alignment angles without projection onto any anatomical plane, were measured using weight-bearing cone-beam computed tomography (CBCT) and compared with conventional 2D radiographic HKA angles. Knees were classified into 3D alignment phenotypes based on their alignment orientation: valgus-extension, valgus-flexion, varus-extension and varus-flexion. Joint space narrowing and Western Ontario and McMaster Universities osteoarthritis index (WOMAC) scores were assessed. For each KL grade, the average spatial HKA orientation was incorporated into finite element models to estimate cartilage stress distributions.
RESULTS
Spatial HKA angles showed stronger correlations with joint space narrowing (r = 0.52-0.61) and WOMAC scores (r = 0.45-0.56) than single-plane alignment measures. Spatial HKA angles increased progressively across KL grades. Knees with mild osteoarthritis clustered near neutral, whereas knees with KL Grades 3 and 4 predominantly shifted toward a varus-flexion pattern. The prevalence of varus-flexion alignment increased markedly with severity, reaching 67.2% and 89.1% in KL Grades 3 and 4, respectively. Medial and posterior cartilage stress increased with severe varus-flexion alignment.
CONCLUSION
The spatial HKA angle derived from weight-bearing CBCT captured severity-dependent multiplanar malalignment and demonstrated stronger structural and symptomatic associations than 2D measures. Advanced KOA was characterized by a dominant varus-flexion alignment phenotype, associated with increased medial and posterior cartilage stress.
LEVEL OF EVIDENCE
Level IV.