The Effect of Aging and Mechanical Loading on the Metabolism of Articular Cartilage.

OBJECTIVE: The morphology of articular cartilage (AC) enables painless movement. Aging and mechanical loading are believed to influence development of osteoarthritis (OA), yet the connection remains unclear.

METHODS: This narrative review describes the current knowledge regarding this area, with the literature search made on PubMed using appropriate keywords regarding AC, age, and mechanical loading.

RESULTS: Following skeletal maturation, chondrocyte numbers decline while increasing senescence occurs. Lower cartilage turnover causes diminished maintenance capacity, which produces accumulation of fibrillar crosslinks by advanced glycation end products, resulting in increased stiffness and thereby destruction susceptibility.

CONCLUSION: Mechanical loading changes proteoglycan content. Moderate mechanical loading causes hypertrophy and reduced mechanical loading causes atrophy. Overloading produces collagen network damage and proteoglycan loss, leading to irreversible cartilage destruction because of lack of regenerative capacity. Catabolic pathways involve inflammation and the transcription factor nuclear factor-κB. Thus, age seems to be a predisposing factor for OA, with mechanical overload being the likely triggering cause.