The purpose of this study is to present a forward kinematics model of the human lumbar spine and to compare the internal loads and trunk flexion extension with existing literature. The forward kinematics model of lumbar spine with 30 DOF was designed using Solidworks and used Matlab to simulate the results for different postures. The forward kinematics model predicted similar trend for trunk flexion extension, compression force, shear forces and moment as described in literature for in vivo studies. The comparison between the proposed model and in vivo measurement showed a pressure difference of less than 15% on the disc L4-L5 for all activities whereas the compression force and moment differed by ~17% on the disc L5-S1. The modeling methodology presented in this thesis provides a more accurate representation of compression forces and moments of the human lumbar spine since the model makes no assumptions regarding muscle force and does not rely on any other software for kinematics data.