This paper introduces a fully compliant spherical joint with an optimized stiffness profile specifically for balancing a pendulum. The design builds on previous work that has successfully created a fully compliant spherical joint using tetrahedron-shaped elements connected in series. To efficiently compute and optimize the balancing behaviour of these compliant joints, a novel algorithm is developed and presented. Using this algorithm, optimizations are conducted to obtain simulated pendulum balancers under five different conditions. The performances of these results are analysed to assess the potential and limitations of the algorithm and these spherical joints. Based on one of the optimized results, a prototype is fabricated and expermentally validated, achieving a moment reduction of 90.5%. The deformation calculated by the TetraFEM tool closely matches the prototype’s deformation with an accuracy of 89.6%, demonstrating its potential for application in the development of shoulder exoskeletons.