Women who have taken bisphosphonate drugs like Fosamax, Actonel, or Boniva for years to prevent osteoporosis fractures are, paradoxically, suffering unusual bone breaks — and the reason comes down to what happens when you suppress the body’s natural bone repair process for too long. These medications work by slowing the breakdown of old bone, which strengthens density in the short term. But after years of use, that suppression can make the femur — the large thighbone that bears most of your body weight — brittle and prone to snapping with little or no trauma. These atypical femoral fractures, as they are clinically known, have sparked thousands of lawsuits, FDA warnings, and a difficult reckoning for patients and doctors who relied on these drugs as a frontline defense against osteoporosis.
For the millions of older women managing both bone loss and cognitive decline, this issue carries particular weight. Dementia caregivers already navigate a maze of medications, fall risks, and mobility concerns. Adding a drug that might quietly weaken the very bones it was prescribed to protect creates a cruel catch-22. A woman with early-stage dementia who has been on Fosamax for a decade may not be able to articulate the dull thigh pain that often precedes these fractures — a warning sign that, if caught early, could prevent a catastrophic break. This article examines exactly how bisphosphonates cause these fractures, who is most at risk, what the latest research and legal developments mean, and what patients and caregivers should discuss with their doctors.
Table of Contents
- How Do Osteoporosis Drugs Cause the Very Fractures They Are Meant to Prevent?
- Who Faces the Highest Risk and When Does the Danger Escalate?
- The Risk-Benefit Equation That Doctors Are Struggling to Balance
- Drug Holidays and What the FDA Now Recommends
- Warning Signs That Caregivers and Patients Should Not Ignore
- The Legal Reckoning Over Fosamax and What It Means for Patients
- Where Bisphosphonate Research and Policy Are Headed
- Conclusion
- Frequently Asked Questions
How Do Osteoporosis Drugs Cause the Very Fractures They Are Meant to Prevent?
Bisphosphonates — including alendronate (Fosamax), risedronate (Actonel), and ibandronate (Boniva) — are the most widely prescribed osteoporosis drugs in the world, and for good reason. Clinical trials have shown they reduce hip and vertebral fractures by 40 to 70 percent. For the first several years of treatment, the math is overwhelmingly favorable. But bone is living tissue, constantly being broken down by cells called osteoclasts and rebuilt by cells called osteoblasts. This remodeling cycle is how your skeleton repairs microdamage from everyday stress. Bisphosphonates work by suppressing the osteoclasts, which slows bone loss but also slows the repair side of the equation. Over years, this over-suppression accumulates.
The femur shaft, which absorbs enormous mechanical load with every step, develops tiny stress fractures that would normally be repaired during healthy remodeling. When that repair process is chemically dampened, those microcracks can quietly propagate until the bone gives way entirely. According to research published in the Cleveland Clinic’s Consult QD, this mechanism explains why atypical femoral fractures tend to occur in the mid-shaft of the thighbone rather than at the hip — the shaft endures repetitive bending forces that demand constant micro-repair. The comparison to a bridge is useful here. Regular maintenance — patching small cracks, replacing worn bolts — keeps a bridge standing for decades. But if you halt all maintenance while traffic keeps flowing, the structure looks intact on the surface while quietly deteriorating underneath. That is essentially what prolonged bisphosphonate therapy does to weight-bearing bones.
Who Faces the Highest Risk and When Does the Danger Escalate?
The risk of atypical femoral fractures is not evenly distributed, and duration of use is the single most important factor. According to data published in the Cleveland Clinic Journal of Medicine, the incidence of these fractures is extremely low during the first three years of bisphosphonate therapy but climbs to 113 per 100,000 patient-years after eight or more years of use. That is a dramatic escalation, and it explains why medical guidelines now emphasize reassessing patients after three to five years rather than keeping them on the drug indefinitely. Women face roughly three times the risk of atypical femoral fractures compared to men, according to a nationwide study published in PMC. After four or more years of use, the age-adjusted relative risk of these fractures reaches a staggering 126-fold in women, with an absolute risk of approximately 11 fractures per 10,000 person-years.
Ethnicity also plays a significant role. Research from Kaiser Permanente found that Asian women have approximately five times the risk of atypical femoral fractures with prolonged bisphosphonate use compared to white women — a disparity that remains poorly understood but may relate to differences in bone geometry and femur curvature. However, if a patient has been on a bisphosphonate for less than three years and has no thigh pain or stress symptoms, the risk of an atypical fracture remains extremely small. The danger is specifically tied to long-term, uninterrupted use, and that distinction matters enormously when weighing whether to continue, pause, or stop the medication. For dementia patients who may have been placed on these drugs years ago and whose medication reviews have lapsed, this is exactly the kind of quiet risk that falls through the cracks.
The Risk-Benefit Equation That Doctors Are Struggling to Balance
The conversation around bisphosphonates is not as simple as labeling them dangerous. For most patients, particularly in the first several years, the benefits far outweigh the risks. A major study published in the new England Journal of Medicine found that after three years, bisphosphonates prevented 149 hip fractures and 541 clinical fractures for every two atypical femoral fractures caused — at least in white populations. That is a ratio most clinicians would accept without hesitation. The problem emerges when treatment extends well beyond that initial window without reassessment. A 72-year-old woman diagnosed with osteoporosis at 60 may have been refilling her Fosamax prescription for over a decade with no one pausing to ask whether she still needs it or whether the risks have shifted.
In a dementia care context, this scenario is alarmingly common. Cognitive decline can disrupt the continuity of medical care, and a drug that was appropriate five years ago may now represent an unacceptable gamble — especially for a patient who is already at elevated fall risk due to balance and coordination problems associated with neurodegeneration. The calculus also differs by individual. A woman with severe osteoporosis and a history of vertebral fractures may genuinely need long-term bisphosphonate therapy despite the atypical fracture risk. A woman with mild bone density loss and no prior fractures probably does not. The trouble is that many patients were never given this nuanced assessment, and the default in clinical practice for years was simply to keep refilling the prescription.
Drug Holidays and What the FDA Now Recommends
The FDA requires bisphosphonate labels to state that the optimal duration of use is uncertain, and the agency recommends that doctors reassess fracture risk after three to five years of therapy. Current clinical guidelines have formalized this into the concept of a “drug holiday” — a planned break from the medication during which residual bone protection from the drug’s long half-life continues to provide some benefit. For patients at low-to-moderate fracture risk, guidelines recommend a drug holiday after five years of oral bisphosphonate use. High-risk patients may continue for up to ten years before pausing, according to a review published in PMC. The encouraging news is that atypical femoral fracture risk drops by approximately 70 percent per year after stopping bisphosphonates, meaning the danger recedes relatively quickly once the drug is discontinued.
There is a meaningful tradeoff between specific bisphosphonates worth noting. Alendronate (Fosamax) users face higher atypical fracture risk than risedronate (Actonel) users, according to 2026 bisphosphonate guidelines. However, alendronate provides more residual bone protection during a drug holiday, meaning bones retain their density longer after stopping. Risedronate’s protective effects fade faster, which may require closer monitoring or earlier resumption of treatment. Neither option is clearly superior — the choice depends on the individual patient’s fracture risk, duration of prior use, and overall health profile.
Warning Signs That Caregivers and Patients Should Not Ignore
Atypical femoral fractures rarely happen without warning. Most patients experience a prodromal period of dull, aching pain in the thigh or groin weeks or even months before the bone actually breaks. This pain is caused by a developing stress fracture and represents a critical window in which imaging can detect the problem and intervention — including stopping the bisphosphonate and sometimes prophylactic surgical stabilization — can prevent a complete fracture. The challenge for dementia caregivers is that patients with cognitive impairment may not report this pain clearly or consistently. They may limp or resist walking without being able to explain why.
They may become more agitated or withdrawn. Caregivers who notice unexplained changes in gait, reluctance to bear weight, or complaints about leg pain in a patient who has been on a bisphosphonate for several years should bring this to a physician’s attention immediately and request imaging of both femurs. Bilateral involvement — stress fractures developing in both thighbones simultaneously — occurs in a meaningful percentage of cases. A limitation worth acknowledging is that standard bone density scans (DEXA) do not detect these stress fractures. An X-ray of the full femur shaft is needed, and even then, early stress reactions may only be visible on MRI. If a doctor dismisses thigh pain in a long-term bisphosphonate user without imaging, that is a red flag worth pushing back on.
The Legal Reckoning Over Fosamax and What It Means for Patients
The legal landscape around bisphosphonate injuries has shifted dramatically. In September 2024, a federal appeals court ruled that atypical femoral fracture cases against Merck, the maker of Fosamax, could proceed to trial. When the U.S. Supreme Court declined to review that decision in June 2025, it cleared the path for more than 500 previously dismissed lawsuits to move forward.
Approximately 3,115 Fosamax lawsuits are now pending against Merck in federal and state courts under a multidistrict litigation consolidated in the District of New Jersey. Merck previously settled roughly 1,200 osteonecrosis of the jaw claims for $27.7 million, but the femoral fracture cases remain unresolved and are being actively litigated. Notably, Organon — which was spun off from Merck in 2021 and acquired Fosamax — has agreed to indemnify Merck against liability from these lawsuits. For patients and families considering legal action, the key question is whether Merck adequately warned about the atypical fracture risk and for how long it knew about the danger before updating its labeling.
Where Bisphosphonate Research and Policy Are Headed
The medical community is moving toward more personalized osteoporosis treatment, and the era of indefinite bisphosphonate prescriptions appears to be ending. Researchers are investigating biomarkers that could identify which patients are most susceptible to bone over-suppression before atypical fractures develop. There is also growing interest in sequential therapy approaches — using bisphosphonates for a defined period and then transitioning to anabolic agents like romosozumab or teriparatide that actively build new bone rather than simply slowing its loss.
For the dementia care community, the broader takeaway is that medication reviews matter profoundly and should happen on a regular schedule regardless of cognitive status. A drug prescribed a decade ago under different circumstances deserves fresh scrutiny, especially when the patient’s risk profile — fall frequency, mobility, ability to communicate symptoms — has changed. The bisphosphonate story is a reminder that even well-intentioned, evidence-based treatments require ongoing vigilance.
Conclusion
Bisphosphonates remain valuable tools for preventing osteoporosis fractures in the short and medium term, reducing hip and spine fractures by as much as 40 to 70 percent. But the evidence is now clear that prolonged use — particularly beyond five years — carries a real and escalating risk of atypical femoral fractures, especially for women, and most acutely for Asian women and those on alendronate specifically. The FDA’s recommendation to reassess after three to five years is not a suggestion to be filed away — it is a clinical imperative that too many patients and providers have overlooked.
For caregivers managing a loved one with dementia, this issue demands proactive attention. Review all current medications with a physician, ask specifically about bisphosphonate duration, and watch for unexplained thigh or groin pain. If your loved one has been on Fosamax, Actonel, or Boniva for more than five years, a conversation about a drug holiday is overdue. The goal is not to abandon fracture prevention but to ensure the treatment itself has not quietly become the threat.
Frequently Asked Questions
How long is it safe to take bisphosphonates like Fosamax?
Current guidelines recommend reassessing after 3 to 5 years. For low-to-moderate risk patients, a drug holiday after 5 years is advised. High-risk patients may continue up to 10 years, but even they should be monitored closely for signs of atypical fracture.
What are atypical femoral fractures and how are they different from normal breaks?
Atypical femoral fractures occur in the shaft of the thighbone, often with minimal or no trauma — a patient may simply be walking when the bone snaps. Normal osteoporotic fractures typically occur at the hip joint or spine and result from falls. Atypical fractures are specifically linked to long-term bisphosphonate-induced suppression of bone remodeling.
What symptoms should I watch for in a family member on long-term bisphosphonates?
Dull, aching pain in the thigh or groin that develops gradually over weeks is the primary warning sign. In dementia patients who cannot articulate pain clearly, watch for limping, reluctance to walk, agitation during movement, or guarding of one leg.
Does the risk go away after stopping the drug?
Yes, atypical femoral fracture risk drops by approximately 70 percent per year after discontinuing bisphosphonates. However, the residual fracture prevention benefit also fades over time, so patients and doctors must weigh both sides.
Are some bisphosphonates safer than others?
Risedronate (Actonel) carries a lower atypical fracture risk than alendronate (Fosamax), but alendronate offers longer-lasting bone protection during a drug holiday. The choice depends on individual risk factors and should be discussed with a physician.
Can I sue over a Fosamax-related femoral fracture?
Potentially, yes. As of 2025, over 3,100 Fosamax lawsuits are pending in federal and state courts, and the Supreme Court’s refusal to block these cases means litigation is actively proceeding. Consult a personal injury attorney who specializes in pharmaceutical cases to evaluate your specific situation.
