Broken tibia/fibia (shin bone/calf bone)

What are the tibia and fibula bones?

The tibia and fibula are the two long bones in the lower leg. They are closely linked at the knee and ankle, but they are two separate bones.

Tibia

• The tibia is the bone that forms the shin and is the larger of the two lower-leg bones.
• The top of the tibia connects to the knee joint and the bottom of the tibia connects to the ankle joint.
• Although this bone carries all the body’s weight, it needs support from the fibula.

Fibula

• The fibula forms the calf bone. It is the smaller bone of the two lower-leg bones and runs parallel to the tibia. 

• The top end of the fibula is located below the knee joint, but is not part of the joint itself. The lower end of the fibula forms the outer part of the ankle joint (it can usually be seen as the bony lump on the outside of the ankle).

• The fibula doesn’t carry much weight, but instead acts as a stabilizer for the tibia.

Learn more about the different types of fractures in children.

Causes

What causes a tibia/fibula fracture in children?

Fractures happen when there’s more force applied to the bone than it can withstand.

• A lower-leg fracture usually happens due to a “high-energy” force from falls, trauma or a direct blow. These are often caused by motor vehicle crashes or by direct contact or sudden twisting in sports.

• Whenever there is a trauma to the leg, the impact spreads between the tibia and fibula. Because both bones absorb the blow, the impact usually results in a combined tibia /fibula fracture. 

• A stress (hairline) fracture may also occur in the fibula, although it is far less common than stress fractures to the tibia, which is a weight-bearing bone. Stress fractures in the tibia/fibula are likely to be caused by repetitive motion, as in running, ballet, baseball and basketball.

Certain risk factors may also increase a child’s chances of getting a broken tibia/fibula.

Signs and symptoms

What are the symptoms of a tibia/fibula fracture in children?

Generally, a tibia/fibula fracture is associated with:

• Pain or swelling in the lower leg area
• An obvious deformity or uneven leg lengths
• Inability to stand or walk (more likely with tibia; less likely if only the fibula is broken)
• Limited range of motion in the knee or ankle area
• Bruising or discoloration (may indicate damage to blood vessels)