Animal legs are capable of a tremendous breadth of distinct dynamic behaviors. As robots pursue this same degree of flexibility in their behavioral repertoire, the design of the power transition mechanism from joint to operational space (the leg) becomes increasingly significant given the limitations current actuator technology. To address the challenges of designing legs capable of meeting the competing requirements of various dynamic behaviors, this paper proposes a technique which prioritizes explicitly encoding a set of dynamics into a robot’s leg design, called dyno-kinematic leg design (DKLD). This paper also augments the design technique with a method of evaluating the suitability of an individual leg’s workspace to perform dynamic behaviors, called the effective dynamic workspace (EDW). These concepts are shown to effectively determine optimal leg designs within a set of three, increasingly complex, case studies on different robots. These new legs designs enable a 5 kg robot to climb vertical surfaces at 3 Hz, allow a 60 kg robot to efficiently perform a range of behaviors useful for navigation (including a run at 2 m/s), and endow a small quadrupedal robot with all of the necessary behaviors to produce running and climbing multimodality. This design methodology proves robust enough to determine advantageous legs for a diverse range of dynamic requirements, leg morphologies, and cost functions, therefore demonstrating its possible application to many legged robotic platforms.