What to Know About the Femur Bone

Medically Reviewed by Mahammad Juber, MD on September 28, 2022
5 min read

The femur is the longest, strongest, and heaviest bone in the human body, making it a difficult one to break. It’s also protected by various muscles and is important, helping you maintain your posture and balance. 

Your femur connects many important muscles, tendons, and ligaments in your hips and knees to the other parts of your body, including areas of the circulatory system. More than that, it helps you carry your body weight when you stand and move. Your femur is critical in helping you maintain stability so you don’t fall over easily.  

Having some basic knowledge about the femur structure and its function could help you recognize its value and avoid possible injury to this part of your body.

The femur is more commonly referred to as the thigh bone. It is the only bone in the upper portion of your leg and is covered all around by your thigh muscles. The adult femur is typically around 18 inches long.

Parts of the femur. The long middle part of your femur is called the femoral shaft. The femoral shaft supports your body weight and forms your thigh structure. It starts below the hip and ends at the knee where the bone begins to widen. This hollow portion of the bone is about an inch and a half thick and has a rounded shape on either end.  

On the femur’s upper end (proximal aspect) are the femoral head and neck. The hip joint connects the head of the femur and the pelvis like a ball and socket. The bone widens at the lower end (distal aspect), which forms the top of the knee joint and connecting to your shin bone (tibia) and patella (kneecap). 

Muscles around the femur. As previously mentioned, your femur is covered on all sides by your thigh muscles, which are divided into three compartments – the anterior, medial, and posterior. The femur is located in the anterior compartment, which is made of the muscles you use to move your hip and extend your knee.   

Within the three compartments are four important muscles, which include:

  • quadriceps (quads) on the front side 
  • hamstrings on the back side 
  • gluteal muscles
  • groin muscles (adductors) on the inner section

Injuries of the femur. As the strongest bone in your body, your femur can support as much as 30 times your body weight. Because it’s so strong, it usually takes a lot of force to break or fracture it. 

To properly fix your femur, you would need to have an operation. Depending on the severity of the injury, your doctor may use strong metal screws and plates, or even long titanium rods, to piece the femur bone back together. These materials are commonly used in surgery today to help heal broken bones in various parts of the body.

The most common problems that affect the femur are fractures, osteoporosis, and patellofemoral pain syndrome.

Femur fractures. If your femur bone was fractured (broken), you would be in a lot of pain. Your femur is an incredibly strong bone, so it would take a huge amount of force to break it. Nonetheless, that happens, and some causes include car accidents and high-impact falls. Common symptoms to look out for include: 

  • Pain 
  • Swelling
  • Tenderness
  • Inability to move your leg normally
  • An abnormal bump on your leg
  • Bruising or discoloration

Common types of femur fractures:

  • Transverse fracture. Femur broken in a horizontal line directly through the shaft. 
  • Oblique fracture. When you break the femur bone at an angle.
  • Spiral fracture. A break that’s caused by a twisting motion in your thigh and forms a fracture line that curls around your bone like a corkscrew.
  • Comminuted fracture. A type of fracture where the bone breaks into more than two pieces. These fractures only happen when there's an extreme amount of force put on the bone.
  • Open fracture. A break that causes the bone fragments to puncture through your skin or a case where the wound passes down to the broken bone. Open fractures are also called compound fractures and they usually cause more damage to the muscles, ligaments, and tendons around your thigh. This means they take longer to heal and carry a greater risk of infections and other complications.

If you do experience a fracture, you’ll likely need surgery to repair your bone and physical therapy to help you regain your strength and ability to move. 

Osteoporosis. Your femur, like all bones, can be affected by osteoporosis – a condition that causes your bones to gradually become weak and brittle. The older you get, the more likely you are to be affected by osteoporosis and the weakening of your bones can make you much more susceptible to fractures in your femur and other bones in your body.

Patellofemoral pain syndrome. This is a condition that causes pain in the front of your knee near the patella (kneecap). It’s sometimes called “runner’s knee” because it usually affects people who play sports that involve running or jumping. The patella sits on a tiny groove at the end of the femur, which is why this syndrome affects both of these structures and the surrounding area.

If there is something wrong with your femur or the surrounding area, you might experience: 

  • difficulty moving the leg
  • inability to stand or walk
  • pain or swelling in the thigh, possibly with bruising
  • deformity (abnormal shape) of the thigh
  • bone pushing out through the skin — sign of a severe fracture

Your femur is a big part of your bone structure, and just like the rest of the bones in your body, it's constantly changing. You build strong and healthy bones in your childhood and adolescent years so that they sustain you through adulthood. As you age, though, your bones start to slightly lose more mass than they gain. 

Luckily, there are ways to prevent or slow this process, some of which include:

  • Getting enough calcium in your diet or taking calcium supplements 
  • Watching your Vitamin D levels
  • Engaging in daily physical activity
  • Staying clear of drugs and tobacco and keeping alcoholic beverages to a minimum 

Be sure to talk to your doctor about any potential concerns you may have about bone health issues like osteoporosis so they can guide you.