Which bone is more slender of the two leg bones?

The fibula is the more slender of the two leg bones. It runs parallel to the tibia and is much thinner in comparison. While the tibia, also known as the shinbone, is the larger and stronger bone that bears most of the weight during activities such as walking and running, the fibula primarily serves to provide stability to the ankle and support for muscles of the lower leg. Its slender shape allows it to play this role without adding much weight to the overall structure of the leg. This anatomical distinction is important for understanding the functions and mechanics of the lower limb.

The patella, although an important bone in the knee joint, is not a bone in the leg itself, and the coccyx is part of the vertebral column. Therefore, they are not considered in comparison when discussing the slenderness of the leg bones.