Limbs not rotating correctly

It was working fine untis suddenly the limbs didn’t rotate, they just deform in some wierd way:(

Here is a picture:


More than likley you have more than one vertex group assigned to the same vertices, i.e. more than one bone is controlling the lower arm mesh. You can check that either in weight paint mode (select the armature, put it into pose mode, then select the mesh, switch to weight paint mode (CTR-TAB, then SH-LMB click on the mesh and the name(s) of the bones/vertex groups will be listed. If there is more than one, that’s the problem. You’ll have to remove the unwanted one either by selecting the un-wanted bone and weight painting the affected mesh areas with Weight=0 or select the mesh in EDIT mode and use the EDIT butons/ Vertex groups panels to choose the verts, then use the Remove button to remove them from the un-desired vertex group.