COMPROMISED TRABECULAR BONE OF THE KNEE IS A DOSE-DEPENDENT CORRELATE OF MORE SEVERE OSTEOPHYTES AND ADVANCED KLG

Abstract

INTRODUCTION

Previous studies have shown that bone turnover is elevated, and fracture risk is higher among knee osteoarthritis (KOA) patients, especially in later stages of disease. While there have been mixed findings with respect to areal bone mineral density (BMD)’s association with KOA severity, it remains unclear how volumetric bone morphometry at the knee is related to the development of radiographic disease features such as osteophytosis and attrition.

OBJECTIVE

It was hypothesized that having definite osteophytosis and attrition are each associated with compromised subchondral bone, including lower volumetric(v) BMD, apparent v.Tissue Mineral Density (vTMD) and a wider Tb.Sp.

METHODS

In this cross-sectional study, women 50-85 years old were recruited by convenience sample if they experienced knee pain ≥3 days a week, each lasting >3 hours, and if self-reported body mass index (BMI) was <30 kg/m². On the knee with worse symptoms, they completed a peripheral quantitative CT (pQCT) knee scan, one slice (2.3±0.5mm, 200µm in-plane) prescribed per tibiofemoral compartment; and an anteroposterior knee X-ray for KLG, including breakdown semi-quantitative evaluation of osteophytosis, attrition, JSN, and sclerosis. pQCT knee images were analyzed using a previously reported iterative threshold-seeking algorithm (Tam et al. Skeletal Muscle 27(14) 2024) to separate trabecular bone from marrow. Apparent structural parameters were derived from bone volume, bone surface, and total volume according to equations by Parfitt’s model of parallel plates. General linear models examined how KLG and osteophyte score, and each of established (score > 2) KOA (KL), osteophytosis, and attrition were related to knee vBMD, vTMD, app: Tb.Sp, Tb.Th, Tb.N, and BV/TV. Models adjusted for age, BMI, use of pain medications, antiresorptives, glucocorticoids or intra-articular steroid injections.

RESULTS

Among 105 women (mean(SD) age: 62.6(9.0)yrs, BMI: 24.2(3.5)kg/m², median KLG: 1(1,2), 41(39.1%) with established KOA), a higher KLG or established KOA were each associated with lower vBMD and vTMD (with effects larger for vTMD), and a larger app.Tb.Sp; though, only in advanced stage (KLG3/4) individuals (Table1). Attrition was only associated with larger Tb.Sp in the lateral femur. Having more advanced osteophytosis was dose-dependently linked to lower vBMD and larger app.Tb.Sp (Figure 1). These effects were only present at the femur and not the tibia, with magnitudes appearing larger in themedial compartment among moderate grade (score 2) knees, but dose-dependently only in the lateral compartment.

CONCLUSION

Among peri- to post-menopausal women without obesity, compromised bone characterized by lower apparent bone density and less intact trabecular structure, may be key correlates of having more advanced radiographic KOA largely driven by osteophytosis. Structural differences may not be adequately apparent in the subchondral tibia using pQCT, perhaps due to damage that may simulate higher bone volume fraction. More sensitive techniques or metrics are needed to distinguish damaged bone from intact but diminished structures.