In　this　paper,　we　present　a　novel　moving　mesh　finite　element　method　for　solving　the　porous　medium　equation,　using　the　Onsager　variational　principle　as　an　approximation　framework.　We　first　demonstrate　that　a　mixed　formulation　of　the　continuous　problem　can　be　derived　by　applying　the　Onsager　principle.　Subsequently,　we　develop　several　numerical　schemes　by　approximating　the　problem　within　a　nonlinear　finite　element　space　with　free　knots　(movable　nodes),　following　the　same　variational　approach.　We　rigorously　prove　that　the　energy　dissipation　structure　is　preserved　in　both　semi-discrete　and　fully　implicit　discrete　schemes.　Additionally,　we　propose　a　fully　decoupled　explicit　scheme,　which　requires　only　the　sequential　solution　of　a　few　linear　equations　per　time　step.　Other　variants　of　the　method　can　also　be　derived　analogously　to　preserve　mass　conservation　or　to　enhance　stability.　The　numerical　schemes　achieve　optimal　convergence　rates　when　the　initial　mesh　is　carefully　chosen　to　ensure　good　approximation　of　the　initial　data.　Through　extensive　numerical　experiments,　we　evaluated　and　compared　the　efficiency　and　stability　of　the　proposed　schemes　with　existing　approaches.　For　cases　involving　uniform　initial　meshes,　all　schemes　exhibit　good　stability,　with　the　fully　decoupled　scheme　demonstrating　superior　computational　efficiency.　In　contrast,　when　addressing　singular　problems　on　nonuniform　meshes,　the　stabilized　explicit　scheme　strikes　a　good　balance　between　stability　and　computational　efficiency.　In　addition,　the　method　inherently　captures　the　waiting　time　phenomenon　without　requiring　user　intervention,　further　illustrating　its　robustness.　©　2025　Elsevier　Inc.