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Objectives: The idea to aim for an "individualized" alignment, whereby the constitutional alignment is restored, has gained much interest among knee surgeons. This requires insight into the prediseased, natural alignment of our patients' knees. The aim of this study is (1) to determine how the hip-knee-ankle (HKA) angle is influenced during the arthritic process and (2) to investigate the correlation between joint line changes and the progression of osteoarthritis (OA). It is our hypothesis that the most pronounced coronal parameter changes appear at the proximal tibia and at the joint line., Methods: One hundred sequential full-length X-rays with a minimum follow-up of 1 year were retrospectively reviewed from a radiographic joint database. Patients had to be at least 50 years of age needed to have an HKA angle of more than 1.3° varus to be included. Patients with ipsilateral total hip arthroplasty, femoral or tibial fracture, osteotomy, or ligamentous repair were excluded. Fifteen alignment parameters were investigated on the sequential full-length X-rays. Moreover, the relationship between the alignment parameters and the Kellgren-Lawrence grade (KL grade) was determined by using linear mixed models., Results: A progressive KL grade is associated with an increase of the HKA (p < 0.001). Mostly, HKA differs due to decrease of the medial tibial plateau (MPTA) angle (0.93°) and an increase of the joint line angle (JLCA) (0.86°). The mLDFA demonstrated the most pronounced changes in the beginning of OA (KL grade 1-2) (p = 0.049). In particular, the MPTA becomes considerably smaller (p = 0.004) in the later stage of OA (KL grade 3). Also, a progressive increase of the JLCA (p < 0.001) is observed upwards of KL grade 3., Conclusion: By comparing consecutive full-length X-rays in the same patients, it is possible to define the coronal alignment changes during the arthritic process. The HKA angle increases according the arthritic progression, whereby the most pronounced changes appear at the proximal tibia (MPTA) and at the joint line (JLCA).The alignment changes in varus OA knees can be divided in three stadia: (1) erosion of the distal medial femoral condyle, (2) erosion of the medial tibial plateau, and (3) a progressive increase of the joint line angle., Level of Evidence: Therapeutic Study, Level III., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Introduction: High-grade varus osteoarthrosis (OA) is characterized by a pronounced intra-articular varus deformity and associated insufficiency of the lateral ligamentous complex. When performing a total knee arthroplasty (TKA) in such a knee, traditionally the alignment is restored to neutral, and the medial soft tissue structures are released to compensate for the lateral laxity and balance the joint. However, another option would be to leave the medial soft tissues untouched and accept the lateral laxity but to compensate for it using an ML-stabilized constrained-condylar knee (CCK) design. Our aim was to prove our hypothesis that such knees would demonstrate better clinical stability and better functionality as well as subjective outcome scores., Materials and Methods: We searched our bicenter database of 912 primary TKAs (from 2016 to 2019) for primary TKA patients with a preoperative varus alignment of > 8°. After inclusion, 60 patients were divided into three groups by implant design: CCK (n = 21), posterior-stabilized (PS) (n = 20) and cruciate-retaining (CR) (n = 19). Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Knee Society Score (KSS), UCLA-activity score, ML instability scores and both radiographic and clinical data were compared between groups., Results: ML stability was significantly better in CCK designs (86% grade 0) compared to CR (37% grade 0) (p = 0.004) but not PS (70% grade 0) designs. No grade II instability was present in CCK and PS implants compared to 16% of CR implants. KSS and UCLA-activity score were higher in CCK designs compared to PS (p = 0.027, p = 0.041) and CR designs (p < 0.001, p = 0.007). OKS and FJS were higher in CCK designs compared to CR (p = 0.025, p = 0.008) but not to PS., Conclusion: The use of a CCK design to compensate for the lateral laxity in high-grade varus OA knees allowed to refrain from a medial release. CCK designs displayed improved clinical stability and better functionality as well as subjective outcome scores compared to less-constrained designs., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Recent studies highlighted the crucial contribution of subchondral bone to OA development. Yet, only limited data have been reported on the relation between alteration to cartilage morphology, structural properties of the subchondral bone plate (SBP) and underlying subchondral trabecular bone (STB). Furthermore, the relationship between the morphometry of the cartilage and bone in the tibial plateau and the OA-induced changes in the joint’s mechanical axis remains unexplored. Therefore, a visualisation and quantification of cartilage and subchondral bone microstructure in the medial tibial plateau was performed. End stage knee-OA patients with varus alignment and scheduled for total knee arthroplasty (TKA) underwent preoperative fulllength radiography to measure the hip-knee-ankle angle (HKA) and the mechanical-axis deviation (MAD). 18 tibial plateaux were μ-CT scanned (20.1 μm/voxel). Cartilage thickness, SBP, and STB microarchitecture were quantified in 10 volumes of interest (VOIs) in each medial tibial plateau. Significant differences (p < 0.001) were found for cartilage thickness, SBP, and STB microarchitecture parameters among the VOIs. Closer to the mechanical axis, cartilage thickness was consistently smaller, while SBP thickness and STB bone volume fraction (BV/TV) were higher. Moreover, trabeculae were also more superior-inferiorly oriented, i.e. perpendicular to the transverse plane of the tibial plateau. As cartilage and subchondral bone changes reflect responses to local mechanical loading patterns in the joint, the results suggested that region-specific subchondral bone adaptations were related to the degree of varus deformity. More specifically, subchondral sclerosis appeared to be most pronounced closer to the mechanical axis of the knee.