Why is osteoarthritis an age-related disease?

Abstract

Although older age is the greatest risk factor for osteoarthritis (OA), OA is not an inevitable consequence of growing old. Radiographic changes of OA, particularly osteophytes, are common in the aged population, but symptoms of joint pain may be independent of radiographic severity in many older adults. Ageing changes in the musculoskeletal system increase the propensity to OA but the joints affected and the severity of disease are most closely related to other OA risk factors such as joint injury, obesity, genetics and anatomical factors that affect joint mechanics. The ageing changes in joint tissues that contribute to the development of OA include cell senescence that results in development of the senescent secretory phenotype and ageing changes in the matrix including formation of advanced glycation end-products that affect the mechanical properties of joint tissues. An improved mechanistic understanding of joint ageing will likely reveal new therapeutic targets to slow or halt disease progression. The ability to slow progression of OA in older adults will have enormous public health implications given the ageing of our population and the increase in other OA risk factors such as obesity.

Figure 1. Relationship between musculoskeletal aging and the development of osteoarthritis

Changes that affect joint structure and function with aging increase the susceptibility to developing osteoarthritis but additional factors (OA factors) are usually also present which lead to the development of symptomatic OA. Reproduced with permission from Hazzard's Geriatric Medicine and Gerontology, Sixth Edition, McGraw Hill Medical, 2009.

Figure 2. Relationship between age in years and the prevalence of radiographic knee OA

Data was extracted from the following studies: Johnston County[12], Framingham[11], NHANES (III)[13], and Zoetermeer[14].

Figure 3. Relationship between age in years and the prevalence of symptomatic knee OA

Data was extracted from the following studies: Johnston County[12], Framingham[11], and NHANES(III)[13].