What Happens When You Break Your Femur?

Breaking your femur sets off a cascade of events that goes far beyond the bone itself. The femur is the largest, strongest bone in your body, and when it fractures, the surrounding muscles, blood vessels, nerves, and soft tissue all take a hit. You lose a significant amount of blood into the thigh, you may go into shock, and the injury almost always requires surgery to repair. Recovery takes months, and the complications that can develop along the way range from blood clots to fat entering your bloodstream. The experience differs depending on where along the femur the break occurs, your age, and how quickly you receive care.

Why the Femur Is So Hard to Break and What It Takes

The femur runs from your hip to your knee and bears most of your body weight when you stand and walk. In healthy adults, it takes a tremendous amount of force to fracture it. High-energy impacts like car crashes, falls from height, and sports collisions are the usual culprits in younger people. Cadaver studies have shown that under impact conditions, the force needed to break the femur is substantially higher than during slow, sustained loading.

For older adults, the story changes. Bones weakened by osteoporosis can fracture from something as simple as a fall from standing height. The vast majority of hip fractures in the elderly are actually fractures of the proximal femur, the part near the hip joint, and they can happen with surprisingly little trauma. This distinction matters because a 25-year-old who breaks their femur in a motorcycle accident and a 78-year-old who breaks theirs tripping on a rug face very different injuries, surgeries, and recoveries.

What Happens in the First Minutes

The pain is immediate and severe. Studies measuring pain scores in patients with femoral shaft fractures have recorded average ratings above 9 out of 10 on a visual analog scale, essentially the upper limit of what patients report.¹ The leg typically appears shortened and rotated because the powerful thigh muscles, which normally pull against the intact bone, now pull the broken ends past each other. You cannot put any weight on it. Even small movements are agonizing.

Internally, you start bleeding right away. The femur has a rich blood supply, and the broken bone ends and torn soft tissue release blood into the thigh compartment. This hidden blood loss is larger than most people realize. A study of hip fracture patients found that the mean drop in hemoglobin before any surgery was performed was about 1.4 g/dL, a clinically meaningful amount of blood loss caused by the fracture alone.² In midshaft fractures, where the marrow cavity is wider and the surrounding muscles create more space for blood to pool, the loss can be even greater. That said, hemorrhagic shock purely from a femoral shaft fracture is uncommon. When a patient with a broken femur is hemodynamically unstable, emergency clinicians are trained to look for other sources of bleeding as well, such as pelvic injuries or internal organ damage.³

Emergency Care Before the Hospital

In the field, paramedics focus on stabilizing the fracture and managing pain. The classic tool is a traction splint, a device that applies a steady pull along the length of the leg to counteract muscle spasm, reduce pain, limit further soft tissue damage from loose bone fragments, and decrease the space inside the thigh where blood can accumulate.⁴ However, traction splints come with contraindications and technical challenges. They should not be used when the fracture is near the hip or the knee, when there is a suspected pelvic fracture, or when there are injuries at the ankle where the traction strap attaches. In those situations, a simple static splint that immobilizes the leg without pulling on it is the safer choice.³

Pain control in the emergency setting can be remarkably effective with a femoral nerve block, an injection of local anesthetic near the nerve that supplies sensation to the front of the thigh. In one study, patients went from pain scores above 9 to below 2 within ten minutes of receiving the block, and the relief lasted an average of nearly four hours with no side effects.¹ This buys time for imaging, transport, and surgical planning without relying solely on systemic painkillers.

Fat Embolism, a Rare but Dangerous Complication

One of the more alarming things that can happen after a femur fracture is fat embolism syndrome. When the bone breaks, fat from the marrow cavity can enter the bloodstream through ruptured veins inside the bone. These fat droplets travel to the lungs and can lodge in the tiny blood vessels there, triggering breathing problems, a rapid heart rate, confusion, fever, and a characteristic rash of tiny red spots called petechiae.⁵ In patients who have an opening between the right and left sides of the heart (a condition called patent foramen ovale, which roughly a quarter of people have without knowing it), fat can cross into the arterial circulation and reach the brain or other organs, causing more severe damage.⁶

The good news is that modern surgical techniques and supportive care have driven the incidence of full-blown fat embolism syndrome down to roughly half a percent of femur fracture cases.⁵ Still, the window of concern lasts from the moment of injury through the first few days after surgery, and medical teams monitor patients closely for early signs during that period.

Surgery and How the Fracture Gets Fixed

Almost every femur fracture in an adult requires surgery. The specific approach depends on where the bone broke. For shaft fractures (the long straight middle portion), the standard treatment is an intramedullary nail: a metal rod inserted through the marrow cavity of the bone, held in place with screws at either end. This allows the bone to share load with the implant, and patients can often begin putting weight on the leg soon after surgery.⁷ For fractures near the ends of the bone, plates and screws fixed to the outside of the bone may be used instead.

Fractures of the femoral neck, the short segment connecting the ball of the hip joint to the shaft, pose a unique challenge. The blood supply to the femoral head (the ball itself) runs along the neck, and a fracture there can cut it off. When that blood supply is disrupted, the bone of the femoral head can die, a condition called avascular necrosis.⁸ The risk of this depends heavily on whether the fracture displaced the bone fragments and how long the patient waits for surgery.⁸ In younger patients, surgeons usually try to save the native hip by pinning the fracture back together. In older patients with displaced fractures, replacing part or all of the hip joint is often the more reliable option, since the risk of avascular necrosis and the need for a second surgery are otherwise high.⁹

The choice among internal fixation, partial hip replacement (hemiarthroplasty), and total hip replacement for older patients with femoral neck fractures remains genuinely debated. A review of national surgical data found no difference in 30-day mortality rates among the three approaches, though internal fixation and hemiarthroplasty were associated with a lower chance of respiratory complications compared to total hip replacement.¹⁰ Practice varies widely between surgeons and hospitals, and each option carries trade-offs in terms of reoperation risk, mobility, and long-term function.¹¹

How the Bone Actually Heals

The way a femur heals depends on how stable the repair is. When an intramedullary nail or plate holds the broken ends in tight contact, healing can occur directly across the fracture line without forming a large visible callus. When the fixation allows some movement between the fragments, which is more common, the body takes a different route. It first lays down a soft cartilage scaffold around the break, which gradually mineralizes and is replaced by real bone. This secondary healing process produces a bulge of new bone called a callus that bridges the gap and eventually remodels to match the original shape.¹²

For a healthy adult with a well-fixed midshaft fracture, expect roughly three to six months before the bone is solid enough for normal activities. But healing does not always go according to plan. When the body’s ability to form new bone is impaired (from poor blood supply, infection, smoking, certain medications, or inadequate stabilization), the fracture may fail to unite altogether. This is called a nonunion, and it sometimes requires additional surgery, bone grafting, or experimental cell-based therapies to jump-start the healing process.¹³

Blood Clots After a Femur Fracture

Venous blood clots are one of the most common serious complications after femur fractures. The combination of major tissue injury, immobility, and the body’s inflammatory response to trauma creates near-ideal conditions for a clot to form in the deep veins of the leg. The risk rises immediately after the injury and stays elevated through surgery and the early recovery period.¹⁴ For elderly patients with hip fractures, the risk is especially high due to their typically weaker immune responses and the prevalence of underlying diseases.

When a clot breaks loose and travels to the lungs, it becomes a pulmonary embolism, which can be life-threatening. Analysis of a national surgical registry found that longer surgeries significantly increased the odds of both deep vein thrombosis and pulmonary embolism. Each additional hour of operative time raised the odds of a clot by roughly 19 percent.¹⁵ Patients with disseminated cancer were at even greater risk, with nearly triple the odds of pulmonary embolism compared to cancer-free patients.¹⁵ Blood-thinning medications are given routinely after femur fracture surgery to lower these risks.

Rehabilitation and Getting Back on Your Feet

After surgery, you will not simply wait for the bone to heal. Modern rehabilitation starts almost immediately. Physical therapy typically focuses on weight bearing as early as the surgical fixation allows, alongside range-of-motion exercises for the hip and knee and progressive strengthening of the muscles that have weakened from the injury and from disuse. A case study of a patient with a midshaft femur fracture found that early weight bearing and aggressive strengthening allowed a return to physically demanding manual labor within six months.¹⁶ That is a best-case scenario in a young, motivated patient, but it illustrates what is possible with modern fixation techniques and early rehab.

For elderly patients, the timeline is much longer and the stakes are higher. Many older adults never fully return to their pre-fracture level of mobility. The enforced immobility and pain contribute to muscle wasting, loss of balance, and fear of falling, which in turn increases the risk of another fall. A significant proportion of elderly hip fracture patients require assistance with daily activities permanently.

The Psychological Toll

The mental health impact of a femur fracture, especially in older adults, is easy to underestimate. Research has consistently found that elderly patients with femoral fractures face heightened rates of anxiety, depression, sleep disorders, and social isolation.¹⁷ The fracture disrupts physical independence, which for many older people is closely tied to their sense of identity and purpose. A review of quality-of-life studies found that hip fractures exert a severe impact on both physical and mental functioning in the majority of elderly patients.¹⁸

This psychological dimension feeds back into physical recovery. Patients who are depressed or anxious participate less in rehabilitation, eat less, sleep worse, and heal more slowly. There is growing recognition in orthopedic and geriatric medicine that psychological support should be a routine part of femur fracture care in older adults, not an afterthought.

Femur Fractures in Children

Children break their femurs too, usually from high-energy trauma like car accidents or falls from playground equipment. Because a child’s skeleton is still growing, the injury behaves differently in several important ways. The bone heals faster than in adults, often in a matter of weeks rather than months. But the growth plates near the ends of the femur, which are responsible for the bone’s lengthening as the child grows, can be damaged. A meta-analysis of growth plate injuries found that roughly half of growth plate fractures led to some degree of growth disturbance, and fractures with displaced fragments had more than four times the rate of growth arrest compared to those without displacement.¹⁹

Paradoxically, children who break the shaft of their femur sometimes end up with the injured leg slightly longer than the uninjured one. The healing process stimulates blood flow to the growth plate, which can accelerate growth temporarily. One study found statistically significant overgrowth (averaging about 3 mm) in children who were between 4 and 8 years old at the time of their fracture, though the effect was not significant in older children.²⁰ Shortening can also occur, depending on the fracture pattern and the child’s age. In a study that followed children after femoral fractures, 38 out of 45 patients with a leg-length discrepancy had overgrowth rather than shortening.²¹ Most of these differences are small enough that they cause no functional problems.

Leg Length Discrepancy in Adults

Adults can also end up with legs of slightly different lengths after a femur fracture, especially when the bone shattered into multiple pieces. Even with careful surgical fixation, getting the length perfectly matched is difficult when the fragments are comminuted. A study of adult patients with complex femur fractures found that nearly all had some measurable discrepancy, with an average of about 0.6 cm. Only about 7 percent had a difference greater than 1.25 cm.²² Discrepancies under a centimeter rarely cause noticeable symptoms, though larger ones can affect gait, contribute to back pain, and require a shoe lift or, in severe cases, further surgery.

The Financial Weight of the Injury

A femur fracture is one of the most expensive fracture types to treat. U.S. hospitalization data for osteoporosis-related fractures found that femoral fractures carried the highest average hospital costs, around $16,400 per stay, with an average length of stay of nearly six days.²³ That figure covers only the initial hospital admission, not the outpatient follow-up, physical therapy, mobility aids, home modifications, or lost wages that follow. In a Dakar teaching hospital, proximal femur fractures accounted for over 43 percent of the total cost of fracture care among elderly patients, outweighing all other fracture types combined.²⁴

The cost extends beyond the patient. A study in Tanzania found that informal caregivers, usually family members, lost an average of 9 percent of their annual income while caring for a hospitalized patient with a femur fracture. Each additional day in the hospital added nearly $5 in direct costs to the caregiver.²⁵ In settings where the patient is the household’s primary earner, the ripple effects through a family can last years.

How Treatment Has Changed Over Decades

The history of femur fracture treatment is a useful reminder of how far orthopedic surgery has come. Before the 1950s, femur fractures near the knee were treated without surgery, using prolonged bed rest and traction. The results were grim: high rates of deformity, stiff joints, and long-term disability.²⁶ The introduction of surgical fixation with metal plates in the 1950s was a turning point, and the techniques have been refined continuously since then. Intramedullary nails, locking plates, and minimally invasive approaches have shortened hospital stays, reduced infection rates, and allowed earlier return to weight bearing. Newer materials like carbon-fiber-reinforced polymer nails are now being tested, with early results showing high union rates, though the evidence base is still small.⁷ The trajectory is clear: what used to mean months in a hospital bed and a lasting limp now often means same-day surgery and walking within 24 hours.

1
PubMed Central. Femoral nerve block for acute pain relief in fracture shaft femur in an emergency ward
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PubMed Central. The hidden blood loss in proximal femur fractures is sizeable and significant
3
PubMed Central. Prehospital Trauma Compendium: Management of Suspected Femoral Shaft Fractures – A Position Statement and Resource Document of NAEMSP
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PubMed Central. Prehospital Traction Splint Use in Midthigh Trauma Patients
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PubMed Central. Fat embolism syndrome after femur fracture fixation: a case report
6
American College of Surgeons. A Feared Complication of Long Bone Fracture: Fat Emboli in Transit
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Orthopedic Reviews. Intramedullary nail: the past, present and the future – a review exploring where the future may lead us
8
PubMed Central. Avascular Necrosis of Femoral Head-Overview and Current State of the Art
9
PubMed. Avascular necrosis of the femoral head after femoral neck fracture
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PubMed. Open reduction internal fixation versus hemiarthroplasty versus total hip arthroplasty in the elderly: a review of the National Surgical Quality Improvement Program database
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Journal of Bone and Joint Surgery. Randomized Comparison of Reduction and Fixation, Bipolar Hemiarthroplasty, and Total Hip Arthroplasty
12
ScienceDirect. Fracture Healing Principles of Fracture Healing
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PubMed Central. Bone fracture healing: cell therapy in delayed unions and nonunions
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PubMed Central. Preoperative deep venous thrombosis (DVT) after femoral neck fracture in the elderly, the incidence, timing, location and related risk factors
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PubMed Central. Time, Tumor, and Thrombosis: Drivers of 30-Day VTE After Femoral Fracture Surgery
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Physical Therapy. Early Rehabilitation Following Surgical Fixation of a Femoral Shaft Fracture
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PubMed Central. Progress of systematic psychological interventions in elderly patients with femoral fractures: A comprehensive review
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PubMed Central. Quality of life and psychological consequences in elderly patients after a hip fracture: a review
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PubMed Central. Pediatric neglected distal femoral fracture with growth arrest
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PubMed. Assessing leg length discrepancy following elastic stable intramedullary nailing for paediatric femoral diaphyseal fractures
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PubMed. Leg length inequality after childhood femoral fractures–permanent or temporary phenomenon?
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PubMed Central. Assessing Leg Length After Fixation of Comminuted Femur Fractures
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Bone Reports. Hospitalizations for osteoporosis-related fractures: Economic costs and clinical outcomes
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PubMed Central. Economic Cost of the Treatment of Fractures Among Old People A Preliminary Study in Dakar Teaching Hospital
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PubMed Central. The Initial Economic Burden of Femur Fractures on Informal Caregivers in Dar es Salaam, Tanzania
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PubMed. Distal femur fractures management and evolution in the last century