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.
Arthroplasty ; Arthroplasty, Replacement, Knee ; Humans ; Knee ; Muscle, Skeletal ; Muscles ; Osteoarthritis ; Quadriceps Muscle ; Range of Motion, Articular ; Ultrasonography

Methods: This cross-sectional study included 361 individuals aged ≥65 years (mean age, 75.0 years) living in a local mountain area and underwent medical check-ups from 2014 to 2018. The survey items included kyphosis index, body mass index, back pain prevalence, back pain Visual Analog Scale score, Oswestry Disability Index, walking speed, grip strength, skeletal mass index, osteoporosis (% young adult mean [YAM]), LOCOMO 5 score, and presence of sarcopenia (Asian Working Group for Sarcopenia). The participants were divided into the N (kyphosis index: <12; n=229, 63.4%), M (kyphosis index: 12–15; n=99, 27.4%), and K (kyphosis index: ≥15; n=33, 9.2%) groups. p -values of <0.05 were considered statistically significant. An association factor of kyphosis (kyphosis index: ≥15) was investigated with logistic regression analysis. Results: Age and LOCOMO 5 scores were significantly higher (p <0.05) and %YAM and walking speed were significantly lower (p <0.05) in the K group than in the M and N groups. Other survey items showed significant differences. Only %YAM (odds ratio, 0.20; 95% confidence interval, 0.04–0.96) was an independent factor associated with a kyphosis index of ≥15. Conclusions Decreased muscle mass and muscle strength would be related to kyphosis; however, no such relations were noted. Bone loss was significantly related to kyphosis. Osteoporosis-induced decrease in vertebral body height is present in the background. Sarcopenia and locomotive syndrome were not related to kyphosis, whereas decreased bone density was independently associated with kyphosis in older individuals living in a mountain area.