The leg is the part of the limb that is between the knee and ankle.

It has 3 compartments: the anterior, the lateral, and the posterior compartment.

All these compartments have different roles in regulating the body movement. 

Tibia and fibula are the bones in the leg that connect the knee and the ankle.

They are arranged in parallel.


 Source: eorthopod.com


As you can see from the picture above, tibia is a lot more massive than the fibula. 


Source: nlm.nih.gov 


Tibia participates in the knee joint formation whereas the fibula doesn't. 

Tibia articulates with the femur at the knee.