Effectiveness of ultrasonographic skeletal muscle assessment in patients after total knee arthroplasty

OBJECTIVES: This study aimed to characterize the skeletal muscles of patients who underwent total knee arthroplasty (TKA) using ultrasonography in order to investigate the effectiveness of ultrasonographic skeletal muscle assessment after TKA. METHODS: This study included 50 TKA patients (TKA group) and 41 residents with osteoarthritis who have not received TKA (non-TKA group). Ultrasonography was used to assess the characteristics of several different muscles. Various postoperative outcomes were evaluated. Muscle thickness (MT) and echo intensity (EI) results were compared among operated knees in the TKA group, nonoperated knees in the TKA group, and more severely affected knees in the non-TKA group. For the TKA group, multiple regression was conducted to examine the association between skeletal muscle characteristics of operated knees and postoperative outcomes. RESULTS: The MTs of the vastus medialis, vastus intermedius, and rectus femoris (RF) were significantly smaller and the RF-EI was significantly greater for both operated and nonoperated knees in the TKA group compared with the non-TKA group (P < 0.017). Several parameters of physical function were significantly poorer in the TKA group than in the non-TKA group (P < 0.05). Multiple regression demonstrated that RF-MT was associated with knee range of motion, knee strength, and physical functional performance in the TKA group (P < 0.05). CONCLUSIONS: The quantity and quality of skeletal muscles were lower in the TKA group than in the non-TKA group. Ultrasonography may be useful for assessing skeletal muscles in TKA patients because MT assessed with ultrasonography was associated with various parameters of physical function.