Adults have between 206 and 213 bones. You use all of them each day to sit, stand and move. Your bones also protect your internal organs and give your body its shape. Bones are usually self-sufficient at maintaining themselves, but health conditions like osteoporosis can make you more likely to break bones or have other complications.


The four types of bones (flat bone, long bone, sesamoid bone and short bone) with examples.
Healthcare providers usually classify bones based on their shape and size.

What are bones?

Bones are your body’s main form of structural support. They’re made of hard, strong tissue that gives your body its shape and helps you move.

Your bones are like the frame under the walls of your home. If you’ve ever watched a home improvement show and seen the internal structure of a house, that’s what your bones are — the supports and beams that keep your body strong and stable.

Your bones are living tissue like any other part of your body. It might not seem like it, but they’re constantly growing or changing and reshaping themselves throughout your life.

Visit a healthcare provider if you feel bone pain (a dull ache that feels like it’s coming from inside your body). Go to the emergency room if you experience trauma or think you might have a broken bone.


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What do bones do?

Your bones support your body at all times. They keep your body stable when you’re not moving and help you move when you’re active.

Bones secure and support lots of important tissue throughout your body. Think about the walls of your home again. Instead of holding drywall, plumbing and wiring in place, lots of tissue connects to your bones, including:

Some bones protect your internal organs. For example, your skull safely encloses your brain, and your ribcage shields your heart, lungs and other organs near your chest.

Bones contain and protect your bone marrow. Bone marrow is a soft, fatty tissue that produces critical cells, including:


Where are bones located?

You have bones throughout your body. They support you from head to toe — literally.

How many bones are in the human body?

Adults have between 206 and 213 bones. Babies are usually born with 270 bones that grow together and fuse into their adult skeleton.

It might be surprising to learn that some people have more bones than others. The range of bones people can have comes from differences in people’s skeletons, such as:

  • Having a different number of ribs.
  • Having fewer vertebrae (the bones in your spine).
  • If you have fewer digits (fingers or toes) than usual, you’ll have fewer bones.


What do bones look like?

Healthcare providers usually classify bones based on their shape and size, including:

  • Long bones: Long bones are exactly what they sound like — the longest bones in your body, especially in your arms and legs. Examples of long bones include the femur (your thigh bone) and the humerus (your upper arm bone). The two bones in your lower leg — the tibia (your shin bone) and fibula (your calf bone) — are also long bones.
  • Short bones: Short bones are thinner and weaker than long bones. The bones in your hands and wrists and the talus bone in your ankle are all short bones.
  • Flat bones: Flat bones are wider and less round than other bones. The plates that make up your skull, your ribs and the clavicle (your collarbone) are flat bones.
  • Sesamoid bones: Sesamoid bones are rooted in tendons or muscles. Other bones are connected to other tissues, but sesamoid bones are embedded directly in them. The patella (your kneecap) and some metacarpal bones in your hands are sesamoid bones.

What are bones made of?

Bones are made of cells and proteins. The cortex is the rigid, hard outer layer. It’s the thick shell you see in most illustrations or photos of bones. Cancellous bone (spongy bone) is inside the cortex. It’s much less dense and more flexible. Cancellous bone contains your bone marrow.

Your bones replace their own cells throughout your life. Special cells called osteoblasts and osteoclasts automatically grow and replace your bone tissue. Osteoblasts form new bone tissue. Osteoclasts break down old bone tissue to make room for new, healthier tissue to replace it.


Conditions and Disorders

What are the common conditions and disorders that affect bones?

The most common issues that affect bones are fractures and osteoporosis.

Bone fractures

A bone fracture is the medical term for a broken bone. You can break a bone in a trauma like a fall, car accident or sports injury.

Go to the emergency room (ER) right away if you’ve experienced trauma or think you have a broken bone. A healthcare provider needs to diagnose and treat bone fractures as soon as possible to make sure your bone heals properly.


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.

People assigned female at birth (AFAB) and adults older than 65 have an increased risk of developing osteoporosis. Talk to a healthcare provider about a bone density test that can catch osteoporosis before it causes a fracture.

What are common treatments for bones?

Usually, your bones won’t need treatment unless you’ve experienced a fracture or another injury. You might need treatment if you’ve been diagnosed with osteoporosis.

Bone fracture treatment

How your fracture is treated depends on which bone is broken and what caused it. You’ll need some form of immobilization — like a splint or cast. You 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.
  • Prescription medications.

Exercise and taking supplements may be all you’ll need to prevent osteoporosis. Your provider will help you find a combination of treatments that’s best for you and your bone health.


How can I keep my bones healthy?

Following a diet and exercise plan that’s healthy for you will help you maintain your bone (and overall) health. Seeing a healthcare provider for regular checkups can also help catch any issues or symptoms that affect your bones as soon as possible.

Talk to your provider about a bone density test if you’re older than 65 or have a family history of osteoporosis.

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.
  • Use a cane or walker if you have difficulty walking or have an increased risk of falls.

Additional Common Questions

What is the longest and strongest bone in the body?

The femur (your thigh bone) is the longest bone in your body. Most adults’ femurs are around 18 inches long.

The femur is also the strongest bone in your body. It can support up to 30 times the weight of your body.

What is the smallest bone in the body?

The three ossicle bones in your ear are the smallest bones in your body. These tiny bones help your hearing by carrying sound vibrations to your inner ear. The malleus (hammer), incus (anvil) and stapes (stirrup) are all less than an inch long. The stapes is the smallest — it’s usually one-tenth of an inch long (3.5 millimeters).

A note from Cleveland Clinic

Whether you’re having a lazy day at home or training for a half marathon, your bones support your body and help you move (or sit still on the couch). All the bones in your body, from the tiny bones in your ear to the long bones in your legs, are important.

Anything you do to maintain your overall health will help keep your bones strong and healthy. Talk to a healthcare provider about a bone density test if you’re older than 65 or have a family history of osteoporosis.

Medically Reviewed

Last reviewed on 08/07/2023.

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