The Correlation Between Gastrocnemius Muscle Thickness And Activity Limitations In Patients With Severe OA

Abstract

Abstract Muscle thickness offers an excellent indicator of maximal force generating capacity, and, accordingly, a reduction in muscle thickness may contribute to muscle weakness; this in turn may be related to functional limitations in patients undergoing total knee replacement. The purpose of this study was to correlate the morphologic changes in the gastrocnemius muscle in relation to muscle activity in subjects with severe knee osteoarthritis (OA), in order to establish an objective means of measuring muscle function and muscle recovery. Two subject groups participated in this study, one group of 10 non-pathological subjects (NP) and a separate group of 10 subjects with severe OA. The muscle thickness (MT) and EMG muscle activity (MA) of the medial gastrocnemius (MG) and lateral gastrocnemius (LG) were assessed using ultrasonography (US) and electromyography (EMG), respectively. The correlation between MA and MT was thus investigated, and linear regression analysis performed to determine prediction equations for muscle activity. The results showed that MA is highly related to MT for both MG and LG in NP subjects. The MA prediction equation based on linear regression analysis resulted in R2 values of 0.90 and 0.95 (p<0.05) for LG and MG, respectively, while in OA subjects, a good correlation was shown between MA and MT within the MG, with R2 = 0.80, though a more moderate correlation was found for LG, with R2 = 0.52. The thickness of the MG was not significantly increased during maximum voluntary contraction (MVC) as compared with the resting state, while the thicknesses of LG significantly increased, from 15 to 22 mm, on moving from resting to MVC. This study thus demonstrated that MG is more useful parameter than LG for the prediction of muscle force generating intensity in patients with severe OA.