Stage-Dependent Changes in Subchondral Trabecular Bone Mechano-Structure in Primary Knee Osteoarthritis with Varus Malalignment.

Background: Reports on subchondral bone mechano-structure in individuals with various stages of knee osteoarthritis (KOA) are limited and often conflicting in contemporary literature. Our study aimed to assess differences in subchondral trabecular bone mechano-structure across late KOA stages in a homogenous group of patients with varus malalignment (confirmed by negative hip-knee-ankle-angle values). Methods: This retrospective cross-sectional study included micro-computed tomography scanning and Vickers micro-hardness testing of 90 bone samples (30 femoral and 60 tibial) collected from 15 adult patients with primary KOA undergoing total knee arthroplasty (TKA). The Kellgren-Lawrence grading system was used to assess the severity of KOA lesions in the included individuals, and bone samples were divided into the following groups: moderate KOA (42 samples from seven patients, age: 70 ± 7 years, females: 3/7) and end-stage KOA (48 samples from eight patients, age: 70 ± 6 years, females: 5/8). Results: Our data revealed site-specific sclerotic alterations in subchondral trabecular bone mechano-structure (thicker trabeculae, coupled with higher bone mineral content and increased bone micro-hardness) in individuals with end-stage KOA compared to moderate KOA, supporting its role in KOA pathogenesis beyond the exclusive cartilage degeneration effect. Our data also revealed that most heterogeneous subchondral trabecular mechano-structure was present in bone samples obtained from the medial part of the tibial and femoral condyle, revealing the substantial effect of mechanical loading during varus knee malalignment. Conclusions: Observed site-specific alterations in subchondral bone mechano-structure in individuals with end-stage KOA supported the role of subchondral sclerosis in primary KOA pathogenesis beyond its exclusive effect on cartilage degeneration.