SIRT1 and osteoarthritis: Based on this evidence, our study aimed to (i) provide a characterization of the expression of mainly cell cycle regulators and relevant factors released by aged cells in the skeletal muscle of elderly patients with osteoporotic bone fracture or patients with osteoarthritis, and (ii) evaluate the expression of SIRT1 to suggest its potential involvement in cellular aging processes that lead to skeletal muscle senescence during aging.