Identification of important interactions between subchondral bone ...

2.3 The pathology of Osteoarthritis
CHAPTER 2: Introduction
OA is a complex disease of the entire joint. It is mainly characterized by the progressive
degradation of articular cartilage, formation of osteophytes (bone outgrowths) and alterations and
thickening of the subchondral bone (fig. 8) 60,61 . The main focus in the past decades has been on
the articular cartilage as the affected tissue and biomechanics as the causative agent. The
alterations in subchondral bone were believed to be secondary to the enforced inactivity.
However, several studies have shown that normal cartilage turnover is dependent on a healthy
subchondral bone 62,63 . Today, it is openly debated whether the pathogenesis of OA originates in
the bone or in the cartilage compartment, and it is not clear to which extend these two
compartments drives disease progression. An increased amount of evidence suggests a strong
coupling between the subchondral bone and the articular cartilage turnover with pathological
processes occurring concurrently in both compartments. Therefore, an optimal intervention
strategy for OA likely includes the targeting of both bone and cartilage compartments that affects
the pathophysiology of the whole joint by modulating and altering the interactions between the
different cell types.
Fig. 8. Illustration of a knee with severe osteoarthritis.
A severe chronic osteoarthritic knee, with eroded cartilage,
eroded meniscus, exposed bone and osteophytes (bone
outgrowths). Adapted with few modifications 64 .
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