Aging-related changes present in the tissues that make up the musculoskeletal system contribute to a number of common chronic conditions seen in older adults. In fact, musculoskeletal disease is the most common cause of chronic disability in people older than age 65 years. This is attributable both to the prevalence of diseases affecting the musculoskeletal system and the central role of the musculoskeletal system in physical function. Despite the prevalence of musculoskeletal disease, however, there is still much to learn about the pathogenesis of these diseases, including the role of aging in their development.
A number of diverse tissues, including muscle, tendon, ligament, cartilage, and bone comprise the musculoskeletal system; aging-related changes, as well as changes secondary to disuse, have been noted to occur in all of these. As in other systems, it is often difficult to separate aging from disuse from disease. Because the musculoskeletal tissues must function in concert for normal joint motion and thereby appropriate movement to occur, it is easy to see why physical function so commonly declines with age. However, it is also clear that regular submaximal stress to the musculoskeletal system through exercise can prevent or slow the age-related decline in physical function as well as improve function of diseased tissues.
There are a number of age-related changes common to tissues of the musculoskeletal system, which have also been noted in other tissues within the body (Table 112-1). Because of the relatively slow turnover rate of cells and matrix components in musculoskeletal tissues, aging-related changes such as the accumulation of advanced glycation end-products (AGEs) in matrix proteins and oxidative damage to cell and matrix components can have particularly profound effects on the aging musculoskeletal system. This chapter reviews aging in each of the major components of the musculoskeletal system including cartilage, muscle, ligaments and tendons, and intervertebral disks. Although bone is a key player in the musculoskeletal system, aging changes in this tissue are discussed in more detail in Chapter 117.
Table 112-1 Genral Mechanisms of Musculoskeletal Tissue Aging |Favorite Table|Download (.pdf)
Table 112-1 Genral Mechanisms of Musculoskeletal Tissue Aging
Accumulation of modified and degraded extracellular matrix components
Increased collagen cross-linking by advanced glycation endproducts
Decreased numbers of mesenchymal stem cells to replace lost cells
Decreased mitogenic response to injury
Decreased synthetic capacity in response to growth factor stimulation
Normal Structure and Function
Articular cartilage is the tissue present on the ends of bones that comprise diarthrodial joints (Figure 112-1). This cartilage serves to provide a smooth surface with a very low coefficient of friction necessary for rapid, painless, and smooth joint motion. During joint motion, the opposing cartilage surfaces, separated by a thin layer of viscous and slippery synovial fluid, easily glide over each other. In addition to providing a form of lubrication for the joint surface, the synovial fluid also ...