Fibula (Calf Bone)

The fibula is the third longest bone in your body. It isn’t weight-baring, but it supports muscles, tendons and ligaments. If your bones are weakened by osteoporosis, you have an increased risk for fractures you might not even know about.

Overview

Labled anatomy of a fibula
The fibula is your calf bone. It's one of two bones in your lower leg.

What is the fibula?

The fibula is your calf bone. It’s the smaller of the two bones in your lower leg. It gives your calf its structure and forms the top of your ankle. Your fibula also supports lots of important muscles, tendons, nerves and ligaments.

Because it’s not as strong as other bones in your leg like your femur (thigh bone) or tibia (shin bone), it’s more common to break your fibula. If you do experience a fracture, you might need surgery to repair your bone and physical therapy to help you regain your strength and ability to move.

Your fibula — like all bones — can be affected by osteoporosis.

Fibula vs. tibia

The fibula and tibia are the two bones that form your lower leg.

The tibia is longer and forms part of your knee at its top (proximal) end and your ankle at its lower (distal) end. The tibia is weight-bearing, which means it supports your body when you stand and move.

The fibula is closer to the outside of your body (lateral) than the tibia. The fibula doesn’t support as much weight and mostly provides structure to your leg.

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Function

What does the fibula do?

Your fibula has several important jobs, including:

  • Forming the structure of your calf and the outside of your lower leg.
  • Supporting your ankle.
  • Supporting muscles and tendons in your leg and ankle.
  • Connecting your knee ligaments to the rest of your lower body.

Anatomy

Where is the fibula located?

The fibula is the smaller of the two bones in your lower leg. The other is the tibia. The fibula runs from just under your knee to your ankle. It’s closer to the outside of your body (lateral) than the tibia.

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What does the fibula look like?

The fibula has a wedge-shaped end where it meets the tibia just below your knee, a long middle shaft and a notch at the bottom where it forms your ankle.

Even though it’s one long bone, your fibula is made up of several parts. These include:

Fibula head (proximal aspect)

The upper (proximal) end of your fibula meets the tibia and moves with it when you move your knee joint.

Fibula shaft

The shaft is the long portion of the fibula that forms the structure of your calf. It’s shaped like a three-sided prism.

Fibula distal aspect

The lower (distal) end of your fibula forms the top of your ankle joint. It meets your tibia and calcaneus (ankle bone).

All of these parts and labels are usually more for your healthcare provider to use as they describe where you’re having pain or issues. If you ever break your fibula — a fibular fracture — your provider might use some of these terms to describe where your bone was damaged.

How big is the fibula?

The fibula is the third longest bone in your body. Only the femur and tibia are longer. Most adults’ fibulae (the plural for fibula) are around 14 inches long.

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Conditions and Disorders

What are the common conditions and disorders that affect the fibula?

The most common issues that affect the fibula are fractures and osteoporosis.

Fibula fractures

A bone fracture is the medical term for breaking a bone. Symptoms of a fracture include:

  • Pain.
  • Swelling.
  • Tenderness.
  • Inability to move your leg like you usually can.
  • Bruising or discoloration.
  • A deformity or bump that’s not usually on your body.

The fibula is sometimes broken in a pattern that’s called an avulsion fracture. This happens when the muscles or ligaments attached to it are jerked or suddenly used. These breaks are also caused by hyperextended knees.

Go to the emergency room right away if you’ve experienced a trauma or think you have a fracture.

Osteoporosis

Osteoporosis weakens bones, making them more susceptible to sudden and unexpected fractures. Many people don’t know they have osteoporosis until after it causes them to break a bone. There usually aren’t obvious symptoms.

Women, people assigned female at birth and adults older than 50 have an increased risk for developing osteoporosis. Talk to your provider about a bone density screening that can catch osteoporosis before it causes a fracture.

What tests are done on the fibula?

The most common test done to check the health of your fibula is a bone density test. It’s sometimes called a DEXA or DXA scan. A bone density test measures how strong your bones are with low levels of X-rays. It’s a way to measure bone loss as you age.

If you’ve experienced a fibular fracture your provider or surgeon might need imaging tests, including:

What are common treatments for the fibula?

Usually, your fibula won’t need treatment unless you’ve experienced a fracture or have been diagnosed with osteoporosis.

Fibula fracture treatment

How your fracture is treated depends on which type it is and what caused it. You’ll need some form of immobilization — like a splint or cast — and might need surgery to realign (set) your bone to its correct position and secure it in place so it can heal.

Osteoporosis treatment

Treatments for osteoporosis can include exercise, vitamin and mineral supplements and medications.

Exercise and taking supplements are usually all you’ll need to prevent osteoporosis. Your provider will help you develop a treatment plan that’s customized for you and your bone health.

Care

Keeping your fibula healthy

Following a good diet and exercise plan and seeing your healthcare provider for regular checkups will help you maintain your bone (and overall) health. If you’re older than 50 or have a family history of osteoporosis, talk to you provider about a bone density scan.

Follow these general safety tips to reduce your risk of an injury:

  • Always wear your seatbelt.
  • Wear the right protective equipment for all activities and sports.
  • Make sure your home and workspace are free from clutter that could trip you or others.
  • Always use the proper tools or equipment at home to reach things. Never stand on chairs, tables or countertops.
  • Follow a diet and exercise plan that will help you maintain good bone health.
  • Use your cane or walker if you have difficulty walking or have an increased risk for falls.

A note from Cleveland Clinic

Even if it doesn’t support your weight, the fibula is important part of your leg. Anything you do to improve your overall health will also help keep your bones strong. Talk to your provider about your osteoporosis risk, and ask them about ways you can support your bones as you age.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 05/23/2022.

Learn more about our editorial process.

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