A locking, unactuated knee is added to the Scout II quadruped robot and trotting gaits are studied. The mechanical design of the knee is presented, trotting algorithms are discussed, and a control approach for a robotic leg with an unactuated knee is developed. A model of a single leg is used to determine appropriate leg trajectory parameters and initial conditions to achieve trots. The single leg system and the complete robot are simulated. Experimental implementation of single leg control and quadruped trotting on Scout II are presented.