The Material Point Method (MPM) is a numerical boundary value problem (BVP) solver developed from particle- in-cell (PIC) methods that discretises the continuum into a set of material points. Information at these material points is mapped to a background Eulerian grid which is used to solve the governing equations. Once solved information is updated at the material points and these points are convected through the grid. The background grid is then reset, allowing the method to easily handle problems involving large deformations without mesh distortion. However, imposition of essential boundary conditions in the (MPM) is challenging when the physical domain does not conform to the background grid. In this research, an implicit boundary method (IBM), based on the work of Kumar et al. [1], is proposed to ensure that essential boundary conditions are satisfied in elastostatic MPM problems.