The objective of this thesis is to develop design approaches and models for prosthetic ankle joints using kinematic models of the human ankle and compliant mechanisms technology. Compliant mechanisms offer several potential design advantages over traditional rigid-body designs including high reliability and low cost. These design advantages are ideal for use in prosthetics. Some prosthetic ankle/foot systems currently on the market have multiple degrees of freedom yet are expensive. Additionally, even though these systems have multiple degrees of freedom, none of them are designed after the actual movements of the biological ankle. In this thesis a two, single degree-of-freedom hinge joint model, which is a kinematic model based on the biological ankle during walking, is used to develop compliant prosthetic ankle joints. The use of the model together with compliant mechanisms may provide the ability to develop highly functional prosthetic ankle joints at a lower cost than current high-performance prosthetic systems. Finally, a design approach for ankles may facilitate future development for knees, hips or other biological joints.