Selected muscle architecture characteristics of the quadriceps and adaptation to total knee arthroplasty
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Muscle architecture has a direct impact on force and excursion capabilities. The use of B-mode ultrasound has proven to be a valid and reliable method of assessing these characteristics in vivo. Muscle thickness (MT), pennation angle (PA), and fascicle length (FL) show adaptation to conditions of muscle enlargement, although the effects of disuse are not clear. Total knee arthroplasty (TKA) is a procedure that is commonly associated with disuse manifested through knee extensor weakness following surgery, and provides a unique model in which to examine the muscle structure/function relationship at the architectural level. In this study, subjects undergoing TKA (n=14) were compared to controls (n=15) using measures of muscle architecture assessed by B-mode ultrasound. Across a three-month time period (including pre- and post-operative in TKA subjects), no significant group × time interactions were observed. Significant angle × region interactions were observed for muscle thickness, pennation angle, and fascicle length. Muscle thickness and pennation angle were increased in the proximal muscle region, and at 70°, while pennation angle was increased in the distal muscle region, and at 0°. Lack of adaptation in muscle architecture characteristics among surgical knees did not correlate with three-month improvements in range-of-motion and Knee Society scores. Distinct adaptations in muscle architecture were not seen after TKA. These results would predict no changes in force and excursion characteristics in this group of subjects. The use of ultrasound can provide information beyond that of a traditional clinical examination and can be used in rehabilitation to help identify and explain potential areas of muscle weakness.