A broken femur is a fracture of the thighbone, the longest and strongest bone in your body. The femur runs from your hip to your knee, averages about 18 inches long in adults, and can support up to 30 times your body weight. Because of that strength, breaking it usually requires serious force, like a car accident or a major fall, and it’s treated as a significant injury that almost always needs surgery.
Why the Femur Is So Hard to Break
The femur is built like a load-bearing column. Its long shaft forms the structure of your thigh and carries your full body weight every time you stand, walk, or run. In a healthy adult, it takes extraordinary trauma to fracture this bone. Car crashes, falls from height, and high-speed impacts are the most common causes in younger people.
For older adults, the picture changes. Osteoporosis gradually thins bone tissue over the years, and conditions like cancer or certain medications can weaken the femur further. In these cases, something as ordinary as tripping and falling can be enough to cause a fracture. The incidence rate reflects this: people 75 and older break their femurs at roughly four times the rate of people between 15 and 49. Globally, there were over 11.5 million femoral fractures (excluding hip fractures) in 2021.
Types of Femur Fractures
Not all femur breaks look the same on an X-ray. The bone can fracture along its shaft, near the hip, or near the knee, and the break pattern itself varies depending on how the force was applied.
- Transverse fracture: A straight horizontal break across the shaft, typically caused by a direct blow.
- Oblique fracture: An angled break, running diagonally across the bone.
- Spiral fracture: A break that twists around the shaft, usually caused by a rotational force like a twisting fall.
- Comminuted fracture: The bone shatters into multiple fragments. This pattern is common in high-energy crashes and is the most complex to repair.
- Open (compound) fracture: A piece of bone pierces through the skin. This carries a high risk of infection on top of the fracture itself.
Doctors classify femur fractures by location (upper, middle, or lower third of the shaft) and by how many fragments are involved. That classification directly shapes the surgical plan.
What It Feels Like
A broken femur is not subtle. You’ll feel immediate, severe pain in your thigh, and you won’t be able to stand or put any weight on the leg. The thigh often looks visibly deformed or shortened because the powerful muscles surrounding the femur pull the broken ends out of alignment. Swelling sets in quickly, and bruising may spread across a large area. In an open fracture, bone may be visible through the wound.
Because femur fractures usually result from high-energy trauma, they often come alongside other injuries to the pelvis, spine, chest, or abdomen. Emergency teams treat the whole picture, not just the broken bone.
How It’s Diagnosed
X-rays of the full length of the femur, including both the hip and knee joints, confirm the fracture and show its pattern. In high-energy injuries, doctors also image the pelvis, chest, and spine to check for fractures that aren’t immediately obvious. A CT scan of the pelvis is particularly important after a high-speed crash because a hairline fracture in the femoral neck (the angled section near the hip) can hide on a standard X-ray and cause serious problems if missed.
Surgery Is Almost Always Necessary
Nearly every adult femur fracture requires surgery. The standard approach is an intramedullary nail: a metal rod inserted down the hollow center of the bone, secured with screws at each end. This method preserves the surrounding soft tissue better than other options, leads to faster healing, and allows earlier movement of the leg. It’s considered the go-to treatment for femoral shaft fractures.
In some cases, surgeons use metal plates and screws attached to the outside of the bone instead, particularly for fractures very close to the hip or knee joint. External fixation, where a metal frame stabilizes the bone from outside the body, is sometimes used as a temporary measure when a patient has other life-threatening injuries that need to be addressed first.
Treatment in Children
Children’s bones heal differently than adults’. Young children with femur fractures can often be treated without surgery using a spica cast, a large plaster cast that wraps from the chest down to the ankle of the injured leg and sometimes extends to the opposite leg for stability. Children’s bones tolerate a surprising degree of misalignment and still remodel into a normal shape as they grow. Shortening up to 2 centimeters and significant angulation can correct on their own over time.
The spica cast typically comes off in 4 to 6 weeks once X-rays show healing, though running and jumping are restricted for about three months. Older children and teenagers with unstable fractures may need flexible metal rods placed inside the bone, similar to the adult approach but with hardware designed for growing bones.
Recovery Timeline
Full recovery from a broken femur takes 4 to 6 months for most adults. The early weeks involve limited or no weight-bearing on the injured leg, depending on the fracture pattern and the stability of the surgical repair. Your surgeon and physical therapist will set a specific timeline for when you can begin putting partial weight on the leg, and that schedule varies from person to person.
Physical therapy starts relatively early, often within days of surgery, with gentle range-of-motion exercises for the hip and knee. As the bone heals, therapy progresses to strengthening the thigh muscles, which lose significant mass during the weeks of limited use. Most people transition from a walker to crutches to a cane over the course of several months. Returning to physically demanding work or sport typically falls toward the later end of the recovery window, and some people notice residual stiffness or aching for a year or more.
Serious Complications to Know About
A broken femur is a major injury, and it carries risks beyond the bone itself.
Blood loss. The femur is surrounded by large blood vessels and thick muscle. A fracture can cause significant internal bleeding into the thigh, sometimes enough to require a transfusion.
Blood clots. Immobility after a femur fracture increases the risk of deep vein thrombosis, a clot forming in the leg veins. If a clot breaks loose and travels to the lungs, it becomes a pulmonary embolism, which is a medical emergency. Hospitals routinely use blood-thinning medication and compression devices to reduce this risk.
Fat embolism syndrome. When a large bone like the femur breaks, fat droplets from the bone marrow can enter the bloodstream and travel to the lungs or brain. This happens in roughly 0.5% to 2% of isolated femur fractures. Symptoms include difficulty breathing, confusion, and a distinctive spotted rash on the chest and neck, usually appearing 24 to 72 hours after the injury. Fat embolism syndrome is fatal in 5% to 20% of cases, which is why hospitals monitor femur fracture patients closely in the first few days.
Non-union. In a small percentage of cases, the bone fails to heal properly and the fracture site remains unstable. This may require additional surgery, sometimes replacing a plate with an intramedullary nail to promote healing.
Leg length difference. Even with good surgical alignment, some people end up with the injured leg slightly shorter or longer than the other. Small differences of a few millimeters are common and rarely cause problems. Larger discrepancies may need a shoe lift or, rarely, further surgery.