In this paper, a new soft finger with a pneumaticactuated movable joint is introduced, optimized and characterized in terms of degrees of freedom, workspace and fingertip force. The finger mainly consists of one soft link as the body and one soft joint as the bending actuator. Due to the additional translation and rotation movement capabilities of the joint carried out by two stepper motors, the finger can bend in any direction while having different lengths. This not only results in more flexibility of the finger dealing with obstacles limiting the workspace but also increases the possible configurations in which the finger can reach and exert force to any specific point in the 3D space. Regulating the air pressure in the hollow space inside the link, the stiffness of the finger and consequently the applied force can vary up to two times. Finite element analysis was used to optimize the joint geometry in order to maximize the bending angle and minimize the joint dimensions. Furthermore, the variations of each design parameter and the consequent effects on the optimization objectives were analyzed. The optimized values of geometrical parameters were then utilized to fabricate a prototype with silicone rubber. Bending angle and tip force tests were conducted on the prototype in order to validate the numerical modeling. The experimental results showed that the finger can exert force up to 650 mN.