The age-related loss of muscle strength, namely dynapenia, is a condition resulting from a loss of muscle mass, motor control impairments and/or innervation problems (activation inhibition), which can be exacerbated by ongoing pathological conditions such as osteoarthritis or musculoskeletal disorders. As the population ages, the need for effective treatments and (surgical and non-surgical) interventions become more apparent. However, before any such measure can be implemented, a deeper understanding of the mechanisms behind dynapenia is necessary. This thesis was carried-out within three research projects focused on the investigation of the mechanisms underpinning the loss of both muscle force and neuromuscular function in the elderly (with a specific focus on arthritic patients), and conducted at the IRCCS Rizzoli Orthopaedic Institute (Bologna, Italy) and at the LISiN laboratory (Torino, Italy).