This paper provides a method for Design (Size) optimization. Finite Element Software provides the Graphical User interface (GUI) to pre-process and post process the optimization variable and results. It deals with the stiffness values for different joints using Finite Element Software. To simulate the joints in Finite element model we need stiffness values to simulate the same. There are so many techniques to find out the stiffness values using known variable. To confirm the stiffness values we have used Design Sensitivity and Optimization technique in MSC.NASTRAN SOL 200. Bush element plays a major role to simulate the joints in Finite element model. To model the simple one dimensional Bush elements we need 6 stiffness values which are 3 translations (Kx, Ky and Kz) and 3 rotations (Kxx, Kyy and Kzz). It is therefore necessary to study the behavior of the joints and its characteristics and controlling factors. The current work is an effort to study the phenomenon of joint stiffness. The focus of study is mainly concentrated on the bush element behavior in Joints. Commercial software MSC.PATRAN/NASTRAN is used to model the bush element and a comparative study between the various joints is performed to understand the same. This paper is intended to provide a practical process to solve real engineering Problems and not for comprehensive review of optimization theory.