Muscle stiffness can be measured using ultrasound shear wave elastography. However, until now only longitudinal muscle fibers have been measured, although muscle properties differ longitudinally and transversely (anisotropy).

The project “Measuring muscle tension?” investigated the longitudinal and transverse stiffness of the individually most painful muscles in knee osteoarthritis during relaxation and activity in comparison to equally old and young control subjects using shear wave elastography.

The subjective perception of the symptoms was assessed using the Knee Osteoarthritis Outcome Score and correlated with longitudinal and transverse stiffness. The test subjects with knee osteoarthritis did not show increased longitudinal stiffness of their painful muscles, but rather lower stiffness, especially when standing. In contrast, there was increased transverse stiffness during relaxation. Perceived and measured stiffness did not correlate. This strengthens the evidence for no objectively increased longitudinal stiffness and no correlation between objective and perceived stiffness in painful muscle tension.

Our study included measurements of transverse stiffness for the first time. This brings the cross-connections between muscle fibers (extracellular matrix) and mechanisms of lateral force transmission into the focus of research on muscle tension.