Why tibia is homologous with radius of forearm?

Answer 1

Ulna is medial to radius in the forearm and tibia is medial to fibula in the shank. However it is tibia which is homologous to radius (not fibula), because the form of those two bones are the same.

Answer 2

The tibia in the lower limb and the radius in the forearm are considered homologous bones because they both have similar developmental origins and perform analogous functions in their respective limbs. They are both long bones that serve as weight-bearing structures, with the tibia supporting the body's weight during standing and walking, while the radius helps to support the forearm and facilitate movements of the hand and wrist. Additionally, both bones exhibit similar anatomical features, such as a shaft and distinct articulations at either end.