Human: What is the difference between a femur, tibia, and fibula? Assistant: 
A femur is the largest bone in the body. It is located in the upper leg and is connected to the hip joint. The tibia is the second largest bone in the body and is located in the lower leg. It is connected to the knee joint. The fibula is the third largest bone in the body. It is located in the lower leg and is connected to the ankle joint.