In this study, Dynamic Magnetic Elastography (DMRE) is applied to a clinical cohort. DMRE scans were carried out in patients with severe OA pre and post-op Total Knee Replacement. Muscle recruitment was identified through increased muscle stiffness. Post operatively, muscle stiffness changes observed during dynamic loading were markedly less compared with their pre-op scan. This study supports the use of personalised targeted physiotherapy in muscle rehabilitation.