Effect of Total Knee Arthroplasty on Sarcopenia in Patients With Osteoarthritis in the Knee

Osteoarthritis, Knee, Sarcopenia

sarcopenia, Osteoarthritis, Total Knee Arthroplasty

Sarcopenia is a wasting disease with the locomotion system in the aged population. It is defined as the decline in muscle mass (lean body mass) and strength with the advance of age. The prevalence of sarcopenia increases with age, reaching an astounding 50% among the population aged over 75 in the United States. Sarcopenia is often associated with frailty, falls, and disability. Studies have found sarcopenia can be a predicting risk factor for fractures in the elderly. In addition, sarcopenia predicted a higher chance of mortality in nursing homes.

Notably, sarcopenia often accompanies with osteoarthritis (OA). However, the relationship between sarcopenia and OA is still unclear. One understanding is that sarcopenia and OA and co-existing conditions. One study identified sarcopenia as one of the risk factors of OA. There is also a study which speculated that OA may inhibit the progression of sarcopenia since they observed OA patients had higher BMP4-positive tissues, which indicated presence of satellites cells that may increase muscle regeneration capabilities. However, more studies suggested that OA may contribute to the development of sarcopenia among the elderly. First, it is observed that the prevalence of sarcopenia among OA patients is higher than among the normal population. Further, cross-sectional studies demonstrated that hip or knee OA are associated with declines in muscle mass and muscle strength. Most interestingly, female patients with knee OA had declined lean body mass in their lower limbs, but not in their upper limbs or trunks. Major risk factors of sarcopenia include malnutrition and lack of physical exercise. Therefore, diet supplementation and exercise potentially provide means to alleviate sarcopenia. Studies have demonstrated that strength training in the elderly can improve sarcopenia by increasing muscle strength, mass, power and quality. Exercise habit in middle age could prevent sarcopenia in elder age, maintaining better scores in grip strength, gait speed, and one-leg standing time. Possible molecular mechanism of exercise on sarcopenia is the upregulated nuclear factor-erythroid 2 p45-related factor 2 (Nrf2)-mediated antioxidant response cascade in skeletal muscle, which protected the muscle from oxygen species-mediated toxicity. OA patients often adopt a sedentary life style to avoid joint pain and stiffness, which probably triggers the dysfunction of Nrf2 -mediated antioxidant response cascade, eventually leading to skeletal muscle atrophy. With the ultimate solution, total knee anthroplasty (TKA), patients with knee OA gradually regain their mobility and greatly increase their social and physical activities. Therefore, one can expect to see improved sarcopenia in patients with knee OA after TKA.

Hong Kong