Wolff's law in action: a mechanism for early knee osteoarthritis.

Andrew J Teichtahl,Anita E Wluka,Yuanyuan Wang,Ali Ghasem-Zadeh,Flavia M Cicuttini,Pushpika Wijethilake

doi:10.1186/s13075-015-0738-7

Abstract

There is growing interest in the role of bone in knee osteoarthritis. Bone is a dynamic organ, tightly regulated by a multitude of homeostatic controls, including genetic and environmental factors. One such key environmental regulator of periarticular bone is mechanical stimulation, which, according to Wolff’s law, is a key determinant of bone properties. Wolff’s law theorizes that repetitive loading of bone will cause adaptive responses enabling the bone to better cope with these loads. Despite being an adaptive response of bone, the remodeling process may inadvertently trigger maladaptive responses in other articular structures. Accumulating evidence at the knee suggests that expanding articular bone surface area is driven by mechanical stimulation and is a strong predictor of articular cartilage loss. Similarly, fractal analysis of bone architecture provides further clues that bone adaptation may have untoward consequences for joint health. This review hypothesizes that adaptations of periarticular bone in response to mechanical stimulation cause maladaptive responses in other articular structures that mediate the development of knee osteoarthritis. A potential disease paradigm to account for such a hypothesis is also proposed, and novel therapeutic targets that may have a bone-modifying effect, and therefore potentially a disease-modifying effect, are also explored.

Highlights

Osteoarthritis (OA) had been considered a disease predominantly affecting articular cartilage
A disease paradigm for primary and secondary knee osteoarthritis OA is a heterogeneous disease with multiple pathways of varied etiologies leading to a common endpoint of joint damage, we propose a “bone adaptation” paradigm with a common final pathway of cartilage damage in both primary and secondary knee OA
As theorized by Wolff’s law, when knee bone is subject to increasing loads, it responds with compensatory geometrical changes, most notably an expansion in subchondral bone cross-sectional area. Paralleling these geometric changes is the remodeling of bone architecture with a long-term increase in periarticular bone mineral density (BMD) and remodeling of the trabeculae network

Summary

Introduction

Osteoarthritis (OA) had been considered a disease predominantly affecting articular cartilage. Obesity and subchondral bone cross-sectional area Obesity is another factor that can increase knee joint loading. This was partly answered in a study of knee OA, wherein baseline medial meniscal extrusion was associated with increased expansion of tibial plateau bone area over the course of 2 years [22].

Results

Conclusion