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