The focus of the work was the evaluation of the real degree of freedom of compliant mechanisms or their correct prediction by means of standard an a new adapted modelling. For this purpose, the widely used Pseudo Rigid Body Model (PRBM) was initially applied, whereby contradictions arise between modelling and real motion behavior. Based on this approach an extension was developed. This allows the structural analysis of flexible elements to be performed realistically. The development engineer is thus provided with an essential aid for the selection of suitable support and coupling conditions for the mechanics synthesis. On the basis of this new replacement model, the fuzzy motion behavior of the compliant mechanisms can also be clarified and solutions for completely constrained structures can be identified.