Sources of pain in osteoarthritis: implications for therapy

Abstract

Osteoarthritis is the leading musculoskeletal cause of disability in western society. Despite this, it is still difficult to gain a precise definition of what osteoarthritis actually is. It is well known that there is a modest correlation between x-ray changes and pain. However, for knee joint structure there is largely consistent evidence that bone marrow lesions, synovitis/effusions and cartilage defects are associated with knee pain and cartilage loss. In addition, muscle strength and obesity predict pain even in the absence of structural knee pathology. Finally, the pain system itself is involved with both pain processing and genetic factors implicated in recent studies. These improvements in basic science have greatly enhanced our understanding that osteoarthritis is an umbrella term for a number of pathways leading to very similar pain and structural outcomes; these outcomes are leading to lesion-specific therapies, which indicate the importance of trying to pinpoint causes of pain in the individual.

Benefit–Risk Assessment of Diacerein in the Treatment of Osteoarthritis

“…It is well known that there is a modest correlation between X-ray changes and pain. However, for the knee joint structure, there is largely consistent evidence that bone marrow lesions, synovitis/effusions and cartilage defects are associated with knee pain and cartilage loss [1]. Thus, it would seem logical to regard knee (and perhaps other forms of) OA as an umbrella term for a number of different pathological processes that result in cartilage loss.…”

“…Its prevalence is increasing markedly because of an ageing population [1]. In all, 10 % of the world's population aged 60 years or older have pain or disability from OA [2].…”

What's new in osteoarthritis pathogenesis?

“…A more recent study suggested the association was also independent of large osteophytes, marked synovitis and macerated meniscal tears suggesting damaged articular cartilage may independently lead to knee pain . This may be mediated by substance P nociceptive fibres, superinduction of cyclooxygenase 2 and prostaglandins or increased load on subchondral bone . Cartilage defects can heal (albeit at low rates after age 45), predict cartilage loss in multiple studies and risk of knee replacement in two studies .…”

“…There is strong human evidence that bone plays an important role in the pathogenesis of osteoarthritis . One of these features, BML, has been recognised as a key component of knee osteoarthritis . A number of studies have linked BML with knee pain.…”

“…They are more common with increasing age, female sex and BMI . Cartilage is aneural, therefore defects in cartilage should not be associated with pain but there is consistent evidence that they are (reviewed in Jones). Cartilage defects correlate strongly with BML suggesting BML and cartilage defects are closely related but both have independent associations with pain .…”