Osteochondral Alterations in Patients Treated with Total Knee Arthroplasty Due to Rheumatoid Arthritis and Primary Osteoarthritis: Cross-Sectional Study with Focus on Elucidating Effects of Knee Malalignment.

Micro-computed tomography assessment of osteochondral microstructural properties of the distal femur and proximal tibia was comprehensively conducted to compare adult patients with knee rheumatoid arthritis (RA) and primary knee osteoarthritis (KOA), with special focus on the effects of knee malalignment. This study encompassed 402 bone samples divided into three groups: the RA group [patients who were subjected to total knee arthroplasty (TKA) due to RA, = 23, age: 61 ± 10 years], the KOA group [individuals subjected to TKA due to KOA, = 24, age: 71 ± 9 years] and the control group [sex-matched cadavers without degenerative knee diseases, = 20, age: 67 ± 11 years]. Our data revealed that the RA, KOA, and control groups differ significantly in osteochondral microstructural properties depending on the knee alignment. Specifically, increasing femoral and tibial cortical porosity, coupled with thinner articular cartilage, were noted in the RA and KOA groups, compared to the controls. Furthermore, larger femoral and tibial cortical pores, lower tibial and femoral subchondral trabecular bone fraction, and thinner tibial articular cartilage were noted in the RA group in comparison to the KOA group, implying that the medial-to-lateral load distribution in the knee joint could be most affected in these patients. Our data illustrated that the thinnest cartilage, a thicker and less porous cortex, along with lower trabecular bone volume, were present in the lateral femoral and tibial condyles of RA individuals with valgus knee alignment. Observed subchondral trabecular microarchitectural alterations could be morphological factors contributing to different effects of surgical treatment and variable implant stability in individuals with RA, warranting further research.