Those massive hindquarters look more daunting than they are, but you need a good starting point. There is more than one way to cut up a hind-quarter, but I like to start by finding the ball joint on the inside of the leg.
Use your knife like a sewing machine and trace the femur from the ball down to the knee. With the initial incision, work your knife around the femur, cutting as close to the bone as possible. The meat should then only hang at each joint. Cut it free.