What is the Difference Between Tibia and Fibula

The main difference between tibia and fibula is that tibia is the inner and the comparatively larger bone of the lower leg, whereas fibula is the second bone of the lower leg, being outer and the smaller. Furthermore, tibia connects the knee to the ankle joint while the head of the fibula occurs below the level of the ankle joint and its lower extremity forms the lower part of the ankle joint. Besides, the tibia is the second largest bone of the human body. 

In brief, the tibia and fibula are the two long bones, which form the lower part of the leg below the knee joint. Generally, the tibia is also known as the shinbone, while fibula is also known as the calf bone.  

Key Areas Covered 

1. What is Tibia
     – Definition, Anatomy, Function
2. What is Fibula
     – Definition, Anatomy, Function
3. What are the Similarities Between Tibia and Fibula
     – Outline of Common Features
4. What is the Difference Between Tibia and Fibula
     – Comparison of Key Differences

Key Terms 

Ankle Joint, Calf Bone, Fibula, Knee, Long Bones, Lower Leg Bones, Shinbone, Tibia 

What is Tibia 

Tibia or shinbone is the second largest bone of the human body, occurring between the knee and the ankle joint. Apart from its larger size, the tibia is the stronger bone, which occurs anterior to the second bone of the lower leg. Also, it occurs closer to the median plane. Significantly, it is a long bone with a diaphysis and two epiphyses. 

Figure 1: Tibia

Furthermore, the upper extremity of the tibia directly involves in the formation of the knee joint. Also, the superior articular surface of the bone contains two facets called medial and lateral facet. In contrast, the lower extremity of the tibia along with the fibula and the talus forms the ankle joint. Typically, the inferior surface of the bone contains five surfaces, inferior surface, anterior surface, posterior surface, lateral surface, and medial surface. Significantly, the medial surface is prolonged downward, and it contains a strong pyramidal process called medial malleolus. 

What is Fibula 

The fibula of the calf bone is the other bone of the lower leg, occurring parallel to the tibia. In comparison, it is thinner than the tibia. However, it has the same length as the tibia. Also, fibula occurs on the lateral side of the tibia. Generally, fibula connects to the tibia by the interosseous membrane, forming a fibrous joint called syndesmosis. Significantly, this joint has very little movement.

Figure 2: Tibia and Fibula

Moreover, the fibula is also a long bone whose upper extremity does not take part in the formation of the knee joint. Also, it places towards the back of the head of the tibia. On the other hand, the lower extremity of the fibula occurs a little forward with respect to the plane of the upper end. Also, it projects below the level of the tibia. Significantly, the lower extremity of the bone forms the lateral section of the ankle joint. 

Similarities Between Tibia and Fibula 

• Tibia and fibula are the two types of long bones, which occur in the lower part of the leg. 
• They compose of a diaphysis and two epiphyses.  
• Both of them occur parallelly below the knee joint and above the ankle joint. 
• Also, they have the same length. 
• They are interconnected by the interosseous membrane. 
• Besides, they provide numerous types for the attachment of muscles. 
• Their function is to stabilize the ankle while providing support to the muscles of the lower leg. 
• They cause lower leg fractures. 
• Generally, tibia fractures are always associated with the fibula fractures due to the transmission of the force through the interosseous membrane. 

Difference Between Tibia and Fibula

Definition 

Tibia refers to the large bone, which occurs in the lower front portion of the leg while fibula refers to the outer and usually smaller of the two bones between the knee and the ankle. 

Also Known as  

Tibia is also known as the shinbone while fibula is also known as the calf bone. 

Size 

Tibia is large while fibula is small. 

Diameter 

Tibia is wider while fibula is thinner. 

Position 

Tibia occurs anteriorly while fibula occurs laterally. 

Articulation 

Tibia connects the knee to the ankle joint while the head of the fibula occurs below the level of the ankle joint and its lower extremity forms the lower part of the ankle joint.

Function 

Tibia bears the bodyweight while fibula stabilizes the ankle joint. 

Conclusion 

Tibia is the second largest bone of the human body. Also, it occurs in between the knee and the ankle joint anterior to the second bone of the lower leg, which is fibula. Importantly, it contributes to the weight-bearing of the body. On the other hand, the fibula is the posterior and the thinner bone, which mainly stabilizes the ankle joint. Therefore, the main difference between tibia and fibula is their anatomy and function. 

References:

1. “The Tibia.” TeachMeAnatomy, Available Here.
2. Barclay, Tim. “Fibula Anatomy and Function.” Innerbody, Available Here.

Image Courtesy:

1. “Tibia – frontal view” By Anatomography – en: Anatomography  (CC BY-SA 2.1 jp) via Commons Wikimedia     
2. “811 Tibia and fibula” By OpenStax College – Anatomy & Physiology, Connexions Web site. (CC BY 3.0) via Commons Wikimedia