Osteoporosis

Overview & Definition

Osteoporosis literally means "porous bone". The 1993 and 2001 Consensus Development Conference definitions, still current, describe it as "a progressive systemic skeletal disease characterised by low bone mass and microarchitectural deterioration of bone tissue, leading to increased bone fragility and a consequent increase in fracture risk." Bone strength — the property that resists fracture — reflects two integrated features: (a) bone mineral density (the amount of mineral per unit volume) and (b) bone quality (the architecture, turnover, damage accumulation, and mineralisation). Bone mineral density (BMD) is the easiest to measure and explains roughly 70 percent of bone strength; the rest depends on microarchitecture, which DEXA cannot directly assess.^[1]

The operational WHO definition, used worldwide and at NEET-PG/INICET, is DEXA-based: in a postmenopausal woman or a man aged 50 years or older, the diagnosis is established by a T-score of minus 2.5 or less at the femoral neck, total hip or lumbar spine. The T-score is the number of standard deviations the patient's BMD lies above or below the young-adult healthy female reference mean. A T-score of minus 2.5 means the BMD is 2.5 standard deviations below that mean.^[1][2]

The clinical skill in osteoporosis is prevention and case-finding: identify and treat at-risk people before the first fracture, because a prior fragility fracture is the strongest single predictor of the next one. The disease is largely silent until fracture, so screening and risk-stratification with DEXA and FRAX are the workhorses. Bisphosphonates are first-line therapy for the great majority; anabolic agents (teriparatide, romosozumab) are reserved for very-high-risk disease (multiple fractures or a very low T-score).^[2]

Classification

Osteoporosis is classified by (a) the underlying cause (primary versus secondary) and by (b) the DEXA T-score, which also distinguishes normal, osteopaenia, osteoporosis, and severe (established) osteoporosis (T-score of minus 2.5 or less plus a fragility fracture).^[1]

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The classical Riggs and Melton clinical classification, although superseded in mechanistic thinking, is still useful at the viva: ^[1]

• Primary Type 1 (postmenopausal) osteoporosis — driven by oestrogen deficiency after the menopause, producing accelerated, high-turnover trabecular bone loss. Predominantly affects women aged 50 to 70. Classical fractures: vertebral wedge/compression and Colles (distal radial).
• Primary Type 2 (senile) osteoporosis — age-related, arising from declining osteoblast formation and osteocyte viability, producing cortical porosity and low-turnover loss in both men and women after about 70. Classical fractures: hip (femoral neck and intertrochanteric) and pelvic. ^[1]

The mechanistic distinction is useful because it predicts both the fracture pattern and the targeted therapy: high-turnover postmenopausal bone loss responds briskly to antiresorptives (bisphosphonates, denosumab), while very low T-score or multiple fractures favour an anabolic-first sequence.^[1]

Epidemiology & Risk Factors

Osteoporosis is the commonest metabolic bone disease, affecting an estimated 200 million people worldwide. Approximately one in three women and one in five men aged over 50 years will sustain a fragility fracture in their remaining lifetime. The female:male ratio for vertebral and hip fracture is roughly 2:1, reflecting the rapid loss of trabecular bone that follows the menopause, but men have a worse post-hip-fracture mortality. The global burden is rising rapidly as the population ages; the annual number of hip fractures globally is projected to rise from about 1.6 million in 1990 to over 6 million by 2050.^[1]

Risk factors cluster into BMD-dependent (factors that lower bone density) and BMD-independent (factors that increase fracture risk at any given BMD — age, prior fracture, fall risk): ^[1]

• Unmodifiable — advancing age, female sex and Caucasian (white) ethnicity; osteoporosis is seen in all groups but is more common in older women.^[27]
• FRAX clinical risk factors — a prior history of fracture, parental history of hip fracture, low body mass index, use of oral glucocorticoids, rheumatoid arthritis and other secondary causes of osteoporosis, current smoking and alcohol intake of 3 or more units daily each contribute to fracture probability whether or not BMD is measured.^[10]
• Glucocorticoid exposure — patients receiving 5 mg/day or more prednisone equivalent for 3 months or longer are the defined at-risk population for glucocorticoid-induced osteoporosis and its prevention trials.^[13]
• Menopause and ageing — the two dominant physiological drivers of primary osteoporosis; fracture rates climb steeply after 55 in women and after 65 in men.^[1][27]

Pathophysiology

Bone is a dynamic tissue that is continually remodelled throughout life in tightly coupled basic multicellular units (BMUs). Three cells cooperate: ^[1]

• Osteoclasts — multinucleated, bone-resorbing cells of monocyte/macrophage lineage.
• Osteoblasts — bone-forming cells of mesenchymal origin that lay down osteoid and mineralise it.
• Osteocytes — former osteoblasts entombed within lacunae in the mineralised matrix; the mechanosensors of bone that detect loading and microdamage and orchestrate remodelling. ^[1]

Coupled remodelling proceeds: osteocyte apoptosis at sites of microdamage triggers osteoclast recruitment and resorption of a packet of old bone, which is then reversal, followed by osteoblast recruitment and bone formation to refill the cavity. In health the volume of bone formed equals the volume resorbed (zero net balance). ^[1]

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^[1]

The RANK-RANKL-OPG axis is the master regulator of osteoclastogenesis and the target of modern antiresorptive therapy: ^[1]

• RANK (receptor activator of NF-kB) is the signalling receptor of the osteoclast system: RANKL/RANK signalling regulates osteoclast formation, activation and survival in normal bone modelling and remodelling.^[11]
• RANKL (RANK ligand) — osteoblastic stromal cells were long known to regulate osteoclast formation, and do so by expressing this member of the TNF superfamily; RANKL engagement of RANK drives bone resorption.^[11]
• OPG (osteoprotegerin) is the second TNF-superfamily member expressed by osteoblastic stromal cells and, together with RANKL, regulates osteoclast formation and bone resorption — the RANKL/OPG system is the key regulator of bone resorption and the target of modern antiresorptive therapy.^[11]
• Denosumab is a fully human monoclonal antibody to RANKL that blocks its binding to RANK, inhibiting the development and activity of osteoclasts and decreasing bone resorption; it is given 60 mg subcutaneously every 6 months.^[4]

The Wnt-LRP5/6-sclerostin axis governs osteoblast activity and bone formation, and is the target of the newer anabolic agents: ^[1]

• Wnt signalling through LRP5/6 co-receptors on osteoblast-lineage cells drives their proliferation, differentiation and bone formation.
• Sclerostin, a glycoprotein produced almost exclusively by mature osteocytes, binds LRP5/6 and inhibits Wnt signalling, suppressing bone formation.
• Romosozumab is a humanised monoclonal antibody against sclerostin — given monthly for 12 months, it produces rapid, large increases in bone formation (anabolic) while modestly reducing resorption — a dual effect.^[5][6]

Pathophysiology by type: ^[1]

• Postmenopausal (Type 1, high turnover) — oestrogen withdrawal removes its tonic restraint on osteoclastogenesis. RANKL rises, OPG falls; osteoclasts are recruited, activated and live longer, producing deep resorption lacunae that perforate trabeculae. Trabecular plates lose struts, become rods, and the connections ("nodes") that confer strength are lost — this is why the vertebra (predominantly trabecular) and distal radius fail first.
• Senile (Type 2, low turnover) — ageing is associated with a decline in osteoblast number and function (mesenchymal stem cells preferentially differentiate into adipocytes rather than osteoblasts), sclerostin accumulation, and accumulation of apoptotic osteocytes. Remodelling becomes inefficient at repairing microdamage. Cortical bone becomes porous, the femoral neck thins, and hip fractures predominate.
• Glucocorticoid-induced — glucocorticoids cause direct osteoblast and osteocyte apoptosis, decrease osteoid formation, increase osteoclast survival via RANKL/OPG tilt, reduce intestinal calcium absorption and increase renal calcium loss (secondary hyperparathyroidism), and suppress gonadotropins (hypogonadism). Fracture risk rises rapidly, within 3 to 6 months of starting therapy and at higher BMD than for postmenopausal osteoporosis. ^[1]

Secondary hyperparathyroidism from chronic vitamin D deficiency (common in the elderly and housebound) drives chronic low-grade PTH-mediated resorption and contributes to both cortical and trabecular loss. ^[1]

Clinical Presentation

Osteoporosis is silent until it complicates — the first manifestation is usually a fragility fracture. Case-finding depends on screening and risk stratification, not waiting for symptoms.^[1]

Vertebral compression fracture — the commonest osteoporotic fracture and often asymptomatic (only about one in three comes to clinical attention). When symptomatic it presents with: ^[1]

• Acute, severe thoracic or lumbar back pain after minimal trauma (lifting, bending, coughing), occasionally radicular.
• Loss of height (over 4 cm prompts vertebral imaging), progressive thoracic kyphosis ("dowager hump"), protuberant abdomen (from loss of lumbar lordosis and abdominal muscle tone).
• Late complications: restrictive respiratory impairment (reduced vital capacity from kyphosis), early satiety and weight loss (gastric compression), reduced exercise tolerance and depression.
• Most heal within 6 to 8 weeks; chronic pain suggests multifracture disease. ^[1]

Hip fracture — the most serious osteoporotic fracture. Typically a low-trauma fall from standing height or less in an older adult, with: ^[1]

• Pain in the groin or lateral hip, inability to weight-bear, shortened and externally rotated leg (in displaced femoral-neck and intertrochanteric fractures).
• Surgical emergency — orthogeriatric co-management, prompt internal fixation or arthroplasty.
• One-year mortality 20 to 30 percent; only about 40 percent of survivors regain their pre-fracture level of independence; many require institutional care. ^[1]

Distal radial (Colles) fracture — typically in younger postmenopausal women (under 65) who fall on an outstretched hand. Produces the dinner-fork deformity (dorsal displacement), pain, swelling and limited wrist movement. Treated by closed reduction and below-elbow cast, occasionally K-wires or volar locking plate. ^[1]

Proximal humeral fracture — fall on outstretched hand or directly onto the shoulder; usually impacted or surgical-neck fractures. Most treated conservatively in a sling. ^[1]

Other fragility fractures — pelvis, proximal femur (subtrochanteric — bisphosphonate-related atypical femoral fracture (AFF) has a distinct prodrome and radiographic pattern), distal femur, ribs, sacral insufficiency. ^[1]

Atypical presentations: ^[1]

• Younger woman (under 50) — consider pregnancy-associated osteoporosis, anorexia nervosa with the female-athlete triad, premature ovarian failure, coeliac disease, Cushing, mastocytosis, connective-tissue disease, prolonged depot-medroxyprogesterone or GnRH analogues, anti-epileptic drugs, glucocorticoids.
• Man of any age — always search a secondary cause: hypogonadism (measure serum testosterone), hyperthyroidism, hyperparathyroidism, myeloma, glucocorticoids, alcoholism, haemochromatosis, hypogonadotropic hypogonadism.
• Elderly housebound patient — vitamin D deficiency with secondary hyperparathyroidism, immobility, multiple comorbidities and polypharmacy, falls risk. ^[1]

Differential Diagnosis

The pivotal step is to distinguish generalised osteoporosis from other metabolic bone diseases that share low BMD, and to identify secondary causes that change management. The key discriminator is that in uncomplicated osteoporosis the serum calcium, phosphate and alkaline phosphatase are normal.^[1]

^{[27] [25] [22] [23] [24] [1]}

Other considerations: transient regional (migratory) osteoporosis (focal, self-limiting, often hip), reflex sympathetic dystrophy / complex regional pain syndrome type 1 (focal periarticular osteopaenia after minor injury), regional migratory osteoporosis, post-traumatic disuse osteopaenia, and idiopathic juvenile osteoporosis (prepubertal, self-limiting). ^[1]

Clinical & Bedside Assessment

A focused structural and functional assessment for osteoporosis covers four domains: ^[1]

1. Anthropometry and skeletal signs:

   • Measure height annually using a stadiometer; height loss of 4 cm or more (or any acute loss) prompts vertebral imaging (lateral thoracolumbar spine X-ray or DEXA-based vertebral fracture assessment, VFA).
   • Occiput-to-wall distance over 5 cm suggests thoracic kyphosis from vertebral collapse; rib-to-pelvis distance reduced.
   • Thoracic kyphosis ("dowager hump"), protuberant abdomen, reduced intercostal spaces. ^[1]

2. Fall risk assessment — every patient with low BMD should be assessed for fall risk:

   • Get-up-and-go test (over 12 seconds indicates increased fall risk), TUG, Romberg, tandem gait, functional reach.
   • Identify intrinsic fall-risk factors: visual impairment (cataracts, multifocal glasses), cognitive impairment, depression, orthostatic hypotension, vestibular dysfunction, neuropathy (diabetes, alcohol), muscle weakness (sarcopenia), urinary urgency, syncope (carotid sinus hypersensitivity, vasovagal, arrhythmia).
   • Extrinsic factors: polypharmacy (especially sedatives, hypnotics, antipsychotics, anticholinergics, opioids, antihypertensives, vasodilators), environmental hazards (loose rugs, poor lighting, no grab-rails, ill-fitting footwear), pets underfoot. ^[1]

3. Identify secondary causes:

   • Oral glucocorticoids — everyone beginning or continuing 3 months or more of glucocorticoid therapy needs fracture-risk assessment; ACR guidance covers initial assessment and reassessment for these patients.^[12]
   • FRAX risk-factor review — rheumatoid arthritis and other secondary causes of osteoporosis are FRAX clinical risk factors; screen for them in every new diagnosis.^[10]
   • In glucocorticoid users, prevention trials defined the at-risk population as 5 mg/day or more prednisone equivalent for 3 months or longer.^[13]

4. Examine for complications and secondary clues:

   • Focal bony tenderness, deformity, kyphosis, rib crowding.
   • Proximal muscle weakness (osteomalacia), proximal myopathy in vitamin D deficiency.
   • Cushingoid features, goitre, hyperreflexia (hyperthyroid), proximal weakness (osteomalacia, Cushing), striae, buffalo hump (Cushing).
   • Signs of underlying cause: anaemia (myeloma), hepatosplenomegaly (mastocytosis, myeloma), skin pigmentation (haemochromatosis). ^[1]

Investigations

The aims of investigation are: (1) confirm the diagnosis and quantify BMD (DEXA); (2) detect occult vertebral fractures (VFA/lateral spine X-ray); (3) stratify fracture risk (FRAX); (4) identify secondary causes (targeted blood and urine tests); and (5) monitor therapy (DEXA, bone turnover markers). ^[1]

1. Dual-energy X-ray absorptiometry (DEXA)

DEXA is the gold-standard investigation for diagnosis and monitoring. Two X-ray beams of different energy are passed through the patient; software subtracts soft tissue and reports the BMD (g/cm squared) at the lumbar spine (L1 to L4), femoral neck, total hip and (sometimes) distal one-third radius. DEXA is quick (under 10 minutes), low-radiation (under 10 microSv), precise and cheap. ^[1]

^[1]

2. Vertebral fracture assessment (VFA) and lateral spine X-ray

About two-thirds of vertebral fractures are silent. VFA (performed on the DEXA machine in lateral projection, very low dose) or a lateral thoracolumbar spine X-ray finds occult vertebral fractures. Indications include: height loss over 4 cm, historical height loss over 6 cm, kyphosis, age over 70 (women) or 80 (men), recent or ongoing glucocorticoid therapy, T-score below minus 1.0. A vertebral fracture of at least 20 to 25 percent height reduction (semi-quantitative grade 1 to 3) is diagnostic of osteoporosis regardless of the T-score and independently raises future fracture risk. ^[1]

3. FRAX — fracture risk assessment

FRAX (the WHO Fracture Risk Assessment Tool) integrates clinical risk factors (with or without femoral-neck BMD) to estimate the 10-year probability of hip fracture and of major osteoporotic fracture (forearm, hip, spine, proximal humerus — a composite of the four classical sites). It is freely available at sheffield.ac.uk/FRAX and embedded in many guidelines.^[7]

The FRAX clinical risk factors, identified from meta-analyses, comprise:^[10]

1. Age and sex (probability rises steeply with age; higher in women)
2. Body mass index (entered as a continuous variable)
3. Prior history of fracture
4. Parental history of hip fracture
5. Use of oral glucocorticoids
6. Rheumatoid arthritis and other secondary causes of osteoporosis
7. Current smoking
8. Alcohol intake of 3 or more units daily^[10]

^[10]

Treatment thresholds vary by country (cost-effectiveness based): ^[1]

• US (National Osteoporosis Foundation / AACE 2020): treat when hip-fracture probability is at least 3 percent OR major-osteoporotic-fracture probability is at least 20 percent on FRAX, or in any patient with a T-score of minus 2.5 or below, or with a fragility fracture of the hip or spine.^[2]
• UK (NOGG, NICE NG211/2024): treatment thresholds are age-dependent — a fixed 10-year probability cut-off is not used; the patient's FRAX score is plotted against age on an "age-intervention threshold" chart, treating when the score exceeds the equivalent risk of a same-aged person with a prior fracture.

4. Secondary-cause workup

Routine bloods in every newly-diagnosed osteoporosis patient: ^[1]

• Serum calcium, phosphate, albumin, alkaline phosphatase, 25-hydroxy-vitamin D, creatinine (eGFR), liver function, full blood count, TSH.
• In men add serum total testosterone (morning), LH, FSH, prolactin (and sex-hormone-binding globulin to calculate free testosterone). ^[1]

Conditional tests (when the history or basic workup suggest): ^[1]

• Intact PTH — if calcium is high or low-normal, or suspected hyperparathyroidism.
• 24-hour urinary calcium — to detect hypercalciuria, hypocalciuria, idiopathic versus secondary disease.
• Serum and urine protein electrophoresis, serum free light chains, immunofixation — if myeloma is suspected (anaemia, raised ESR, lytic lesions, renal impairment).
• Coeliac serology (anti-tissue transglutaminase IgA, total IgA) — especially in iron-deficiency, weight loss, diarrhoea, family history, type 1 diabetes, autoimmune thyroid disease, Down syndrome, dermatitis herpetiformis.
• Cortisol (24-hour urinary free cortisol, dexamethasone suppression, midnight salivary cortisol) — if Cushing suspected.
• Serum tryptase — mastocytosis.
• Bone marrow biopsy — if myeloma/mastocytosis suspected.
• IL-23, genetic testing — rare monogenic causes. ^[1]

5. Bone turnover markers (BTMs)

• Serum CTX (C-terminal telopeptide of type I collagen) — marker of bone resorption.
• Serum P1NP (propeptide of type I procollagen) — marker of bone formation.
• Used optionally to monitor adherence and treatment response (CTX falls within weeks of starting an antiresorptive; P1NP rises within weeks of starting an anabolic). Not used for diagnosis.
• Sample in the fasting morning state (CTX has a diurnal rhythm). ^[1]

6. Other imaging

• Plain X-ray — for symptomatic fracture; lateral spine for suspected vertebral compression; shows wedge, endplate or crush deformity; may show intravertebral gas (Kummell), sclerotic end-plates in healing. AP and lateral of long bones for suspected atypical femoral fracture (lateral cortical thickening, "beaking", transverse subtrochanteric or diaphyseal fracture).
• MRI spine — acute versus old vertebral fracture (oedema in acute), exclude malignancy or infection.
• CT — fracture detail, lytic/sclerotic lesion characterisation, vertebral augmentation planning.
• Bone scan / PET-CT — multifocal metastatic disease.
• Quantitative CT (QCT) — research, and in obese patients where DEXA artefact is problematic.
• Trabecular bone score (TBS) — texture analysis of DEXA image; augments FRAX.
• HR-pQCT — research tool assessing microarchitecture. ^[1]

Management — Resuscitation

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Osteoporosis itself rarely presents as an acute emergency; the resuscitation phase applies to the acute fragility fracture, particularly the hip:^[1][2]

1. Acute hip fracture is a surgical and orthogeriatric emergency:

   • Prompt analgesia (opioid-sparing: paracetamol, low-dose opioid, regional/fascia-iliaca block), oxygen, IV fluids, optimisation of comorbidities (heart failure, AF, diabetes, anticoagulation).
   • Surgery within 36 hours (NICE/AAOS) — internal fixation (cannulated screws, dynamic hip screw, intramedullary nail) or arthroplasty (hemiarthroplasty or total hip replacement for displaced femoral-neck fractures in cognitively intact, ambulant patients).
   • Co-managed orthogeriatric care (Rapid-recovery / Hip-fracture pathway) reduces mortality and length of stay.
   • VTE prophylaxis (LMWH, fondaparinux) until mobile.
   • Pressure-area care, delirium prevention, early mobilisation, physiotherapy, nutritional support, falls review. ^[1]

2. Acute painful vertebral fracture:

   • Stepwise analgesia — calcitonin has proven analgesic efficacy in the acute pain of osteoporotic vertebral fractures (demonstrated for intranasal, parenteral and rectal administration in double-blind placebo-controlled trials).^[19]
   • Vertebroplasty or kyphoplasty — percutaneous vertebral augmentation for intractable pain or progressive vertebral collapse; kyphoplasty uses a balloon tamp whose void allows more viscous cement and lowers extravasation risk.^[20]
   • Start specific osteoporosis therapy — with anabolic agents considered for very-high or imminent fracture risk.^[1]

3. Prevent complications of immobility: VTE prophylaxis, pressure-area care, pneumonia prevention, falls reduction. ^[1]

4. Initiate osteoporosis-specific therapy as soon as the acute fracture is managed. IV zoledronate 5 mg yearly, first administered within 90 days after surgical repair of a hip fracture, reduced the rate of any new clinical fracture by 35 percent and all-cause mortality by 28 percent (median follow-up 1.9 years).^[8]

Management — Definitive & Stepwise

Definitive management of osteoporosis has two pillars: (A) universal lifestyle and nutritional measures for all patients, and (B) drug therapy in those who meet treatment thresholds.^[1][2]

A. Universal baseline (all patients)

• Adequate calcium and vitamin D — the universal foundation for every osteoporosis patient. Note the evidence nuance: in a meta-analysis of 33 randomised trials in community-dwelling older adults, supplemental calcium, vitamin D or both were NOT associated with a lower risk of hip or other fractures — correct documented deficiency and emphasise adequate intake, but do not rely on routine supplements alone.^[30]
• Weight-bearing and resistance exercise, smoking cessation, alcohol moderation and falls-risk reduction are the other universal measures for bone health.^[27]
• Glucocorticoid users — lifestyle measures with calcium and vitamin D are recommended for every patient on long-term glucocorticoids.^[12]

B. Drug therapy — when to treat

Treat with pharmacotherapy when any of the following holds:^[2]

• A fragility fracture of the hip or spine (regardless of BMD).
• A T-score of minus 2.5 or less at the femoral neck, total hip or spine.
• A T-score between minus 1.0 and minus 2.5 (osteopaenia) AND a 10-year FRAX probability of at least 3 percent for hip fracture or at least 20 percent for major osteoporotic fracture.
• Patients on chronic glucocorticoids at high risk (see Glucocorticoid-induced osteoporosis below). ^[1]

C. Antiresorptive therapy — bisphosphonates first-line

Bisphosphonates are the most commonly used medications for osteoporosis.^[21]

• Alendronate — in the Fracture Intervention Trial (2027 postmenopausal women with existing vertebral fractures, 36 months), alendronate reduced new morphometric vertebral fractures by 47 percent (relative risk 0.53), hip fracture by 51 percent (relative hazard 0.49), wrist fracture by 48 percent and any clinical fracture by 28 percent (relative hazard 0.72).^[3] Alendronate is given as a 70 mg once-weekly oral formulation, therapeutically equivalent to daily dosing.^[28]
• Risedronate — 5 mg daily for 3 years in the VERT trial (2458 women with at least one vertebral fracture) reduced new vertebral fractures by 41 percent and nonvertebral fractures by 39 percent; all subjects also received calcium 1000 mg daily.^[17]
• Zoledronic acid 5 mg IV once yearly — first infused within 90 days after hip-fracture repair, reduced new clinical fractures by 35 percent and all-cause mortality by 28 percent; pyrexia, myalgia and musculoskeletal pain were the most frequent adverse events.^[8]
• Ibandronate — daily oral administration has proven antifracture efficacy for vertebral fracture, and once-monthly oral dosing regimens were at least as effective as daily dosing for BMD over 1 year in the MOBILE study.^[18]

Long-term bisphosphonate therapy and the drug holiday — the ASBMR task force frames treatment duration as a risk-benefit decision: in the FLEX extension, 10 years of alendronate produced fewer clinical vertebral fractures than switching to placebo after 5 years; in the HORIZON extension, 6 annual zoledronic-acid infusions produced fewer morphometric vertebral fractures than stopping after 3. A low hip T-score predicted benefit from continued therapy, so higher-risk patients continue while lower-risk patients may pause treatment.^[21]

D. Denosumab — alternative antiresorptive

Denosumab 60 mg subcutaneously every 6 months is a fully human monoclonal antibody against RANKL that blocks its binding to RANK, inhibiting the development and activity of osteoclasts. In the FREEDOM trial (7868 postmenopausal women with T-score less than minus 2.5), denosumab over 36 months reduced vertebral fracture by 68 percent, hip fracture by 40 percent and nonvertebral fracture by 20 percent.^[4]

Critical safety rule: never stop denosumab without a transition antiresorptive — discontinuation causes a rebound increase in bone turnover and rapid bone-mineral-density loss, and rebound-associated vertebral fractures after stopping denosumab have been widely reported, including multiple fractures within months of the last injection.^[14]

E. Anabolic therapy — for very-high-risk disease

Anabolic agents are used in patients with very high or imminent fracture risk and are followed by an antiresorptive to consolidate gains.^[1]

• Teriparatide (PTH 1-34) 20 micrograms subcutaneously daily — in the Neer trial (1637 postmenopausal women with prior vertebral fractures, median 21 months) new vertebral fractures occurred in 5 percent versus 14 percent on placebo (relative risk 0.35) and nonvertebral fragility fractures were roughly halved (relative risk 0.47); a 40-microgram dose raised BMD more without greater antifracture effect and caused more side effects.^[9]
• Romosozumab 210 mg subcutaneously monthly for 12 months — binds sclerostin, increasing bone formation and decreasing bone resorption. FRAME: 73 percent lower vertebral-fracture risk and 36 percent lower clinical-fracture risk at 12 months versus placebo. ARCH: romosozumab followed by alendronate versus alendronate alone gave 48 percent fewer vertebral, 27 percent fewer clinical, 19 percent fewer nonvertebral and 38 percent fewer hip fractures over 24 months.^[5][6]
• Abaloparatide — a further anabolic option among current osteoporosis therapies.^[1]

F. Other antiresorptive agents

• Raloxifene — a selective oestrogen receptor modulator. In the MORE trial (7705 postmenopausal women with osteoporosis), raloxifene 60 mg daily for 3 years reduced new vertebral fractures (relative risk 0.7) while nonvertebral-fracture risk did not differ significantly from placebo; it increased spine and femoral-neck BMD.^[15]
• Hormone replacement therapy (combined oestrogen plus progestin) — the Women's Health Initiative (16608 healthy postmenopausal women) was stopped early at a mean 5.2 years because overall health risks (invasive breast cancer HR 1.26, coronary heart disease HR 1.29, stroke HR 1.41, pulmonary embolism HR 2.13) exceeded benefits — so combined HRT is not used as a primary osteoporosis-prevention strategy.^[16]
• Calcitonin — niche role for acute vertebral-fracture pain as above.^[19]

G. Drug holiday

After 3 to 5 years of oral bisphosphonate therapy (or 3 years of IV zoledronate), reassess. In a stable, lower-risk patient (T-score above minus 2.5, no recent fracture, no new risk factors), consider a planned drug holiday of 1 to 2 years, exploiting the prolonged skeletal retention of bisphosphonates. Reassess with DEXA at 1 to 2 years; resume therapy if T-score falls significantly (typically by 5 percent or more), or a fracture occurs, or fracture risk rises. Higher-risk patients (very low T-score, prior hip fracture, multiple fractures) should continue without a holiday. ^[1]

H. Monitoring

• DEXA every 1 to 3 years (longer intervals in stable patients) to confirm treatment response (T-score stable or rising).
• Reinforce adherence at every visit — non-adherence is the single biggest real-world barrier.
• Bone turnover markers (CTX, P1NP) — optional; a fall in CTX within 3 to 6 months of starting an antiresorptive, or a rise in P1NP within 3 months of starting an anabolic, confirms biological response.
• Annual height measurement; VFA/lateral spine X-ray if height loss over 4 cm or back pain.
• Dental review before bisphosphonate initiation (theoretical ONJ risk). ^[1]

Specific Subtypes & Scenarios

• Postmenopausal osteoporosis (primary Type 1) — the dominant phenotype; fracture rates climb steeply in women after 55. Treat with bisphosphonates first-line and reassess treatment duration with a risk-benefit approach to continuation or holiday.^[1][21]
• Senile osteoporosis (primary Type 2) — fractures continue to rise with age in men as well (after 65); where oral adherence is poor, yearly IV zoledronic acid after hip fracture reduces both new fractures and mortality.^[1][8]
• Glucocorticoid-induced osteoporosis (GIOP) — glucocorticoid-induced bone loss is rapid, so assess and treat early. The 2017 ACR guideline addresses adults beginning or continuing 3 months or more of glucocorticoids: calcium and vitamin D alone for those at low fracture risk, with an additional osteoporosis medication (oral bisphosphonate first) at higher risk.^[12] In a 36-month randomised trial of patients on 5 mg/day or more prednisone equivalent for 3 months or longer, teriparatide raised lumbar-spine BMD more than alendronate (11.0 versus 5.3 percent).^[13]
• Male osteoporosis, juvenile osteoporosis, pregnancy-associated, disuse and transplant-related bone loss — apply the same case-finding principles, look hard for secondary causes (FRAX groups them as "secondary causes of osteoporosis"), and treat to the same risk-based thresholds.^[10][1]

Complications & Pitfalls

• Fragility fractures — the central complication. Hip (20 to 30 percent one-year mortality, loss of independence, institutionalisation, postoperative pneumonia, VTE, pressure ulcers, infection); vertebral (acute pain, chronic pain, kyphosis, restrictive respiratory impairment, reduced vital capacity and FEV1, early satiety, depression, 2-fold to 9-fold risk of a further vertebral fracture within a year); Colles (pain, deformity, malunion, complex regional pain syndrome, median nerve injury); proximal humeral (malunion, frozen shoulder).
• Kyphosis with reduced vital capacity and early satiety from vertebral body collapse.
• Loss of independence and institutionalisation after hip fracture.
• Long-term bisphosphonate: atypical femoral fracture (AFF) — stress-type fracture in the subtrochanteric or diaphyseal femur in patients on long-term (over 3 to 5 years) potent bisphosphonates; presents with prodromal thigh or groin pain, often bilateral; characteristic radiographic features: lateral cortical thickening ("beaking"), transverse fracture line, minimal trauma. Manage with discontinuation of bisphosphonate, orthopaedic fixation, calcium and vitamin D, and switch to an alternative (e.g. teriparatide may speed healing).
• Osteonecrosis of the jaw (ONJ) — exposed necrotic mandibular or maxillary bone for over 8 weeks in a patient on a bisphosphonate (or denosumab) without local malignancy or radiation therapy; rare in osteoporosis doses (about 1 in 10,000 to 1 in 100,000), more common in oncology high-dose use. Risk reduced by good dental hygiene, completing dental work before starting therapy.
• Denosumab discontinuation — rebound multiple vertebral fractures — a non-negotiable pitfall: always transition to a bisphosphonate on stopping.
• Teriparatide — avoid in prior skeletal radiation or malignancy (theoretical osteosarcoma risk; absolute risk in humans appears very small — the FDA relaxed the boxed warning in 2020).
• Romosozumab — cardiovascular risk — avoid in patients with recent (within 1 year) myocardial infarction or stroke (per ARCH/FDA label).
• Atrial fibrillation (rare, mostly with IV zoledronate) and acute-phase reaction (fever, myalgia, arthralgia for 24 to 72 hours after IV bisphosphonate).
• Hypocalcaemia — risk with denosumab and zoledronate, especially in CKD or severe vitamin D deficiency; correct vitamin D and calcium before antiresorptive therapy.
• Treatment failure — defined as 2 or more fractures or significant BMD decline despite 12 months of adherent therapy; reassess for secondary causes, adherence, malabsorption, vitamin D deficiency, and consider switching to an anabolic agent. ^[1]

Prognosis & Disposition

Osteoporosis is preventable and treatable but not cured. With effective therapy, vertebral-fracture risk falls by 40 to 70 percent and hip-fracture risk by 25 to 50 percent over 3 years. A prior fragility fracture roughly doubles the future fracture risk; the strongest single predictor of a future fracture is a recent one, so the time after a fracture is a high-risk "fragility fracture gateway" that demands prompt assessment and treatment. ^[1]

Hip fractures carry a one-year all-cause mortality of 20 to 30 percent (worse in men, with comorbidity and cognitive impairment), and a major loss of independence — only about 40 percent of survivors regain their pre-fracture level of mobility, and 20 to 30 percent require long-term institutional care. ^[1]

Vertebral fractures carry an 8-fold increased risk of further vertebral fracture within 1 year and an age-adjusted mortality excess — the more severe and numerous the fractures, the worse the prognosis. ^[1]

Early detection (DEXA, FRAX), good adherence to therapy, fall prevention and prompt management of fragility fractures transform the outlook. Non-adherence is the single biggest real-world barrier: oral bisphosphonate persistence at 1 year is only 30 to 50 percent in routine practice. ^[1]

Disposition: most osteoporosis care is outpatient / primary care, with rheumatology or endocrinology referral for young or male patients, treatment failure, complex secondary causes, consideration of anabolic therapy, or severe disease. Acute hip fracture is a surgical emergency with orthogeriatric co-management. Acute painful vertebral fracture may need inpatient analgesia or vertebroplasty/kyphoplasty. ^[1]

Special Populations

• Glucocorticoid users — fracture risk rises rapidly (within 3 months) and at higher BMD than postmenopausal disease. Prophylax from the outset: calcium and vitamin D for all; add an oral bisphosphonate (alendronate, risedronate) for medium- to high-risk patients (FRAX-adjusted). Teriparatide is superior to alendronate in GIOP for vertebral fracture prevention.
• Chronic kidney disease — bisphosphonates are contraindicated below eGFR 30 to 35 (acute tubular necrosis). Prefer denosumab (non-renal clearance, but watch for hypocalcaemia, especially in CKD stage 4 to 5D — replete vitamin D and calcium first), or teriparatide (no renal dose adjustment). Dialysis patients need CKD-MBD assessment first (PTH, calcium, phosphate) — many have low-turnover (adynamic) bone disease in which antiresorptives can harm.
• Pregnancy and lactation — pregnancy- and lactation-associated osteoporosis is rare, presents with vertebral fractures in late pregnancy or postpartum; conservative management (analgesia, bracing, calcium and vitamin D); avoid bisphosphonates (long skeletal half-life). Teriparatide has been used in severe cases (limited data).
• Elderly / frail — falls risk, polypharmacy, malnutrition and sarcopenia dominate the picture. Multifactorial fall-prevention programmes, vitamin D supplementation (prevents falls in deficient elderly), hip protectors, calcium, and IV zoledronate (also reduces mortality post-hip-fracture) are preferred over oral bisphosphonates when adherence is poor.
• Immunocompromised / transplant recipients — high fracture risk; prophylactic bisphosphonate from pre-transplant through the first 12 months.
• Men — always measure testosterone; hypogonadism is common and reversible. Bisphosphonates (alendronate, risedronate, zoledronate), denosumab and teriparatide are all approved in men.
• Children / adolescents — use Z-score (not T-score); a Z-score below minus 2.0 with a fragility fracture warrants investigation for secondary causes (glucocorticoids, immobility, hypogonadism, anorexia, cystic fibrosis, inflammatory bowel disease, osteogenesis imperfecta, idiopathic juvenile osteoporosis). Treat the underlying cause; bisphosphonates only under specialist supervision in severe progressive disease. ^[1]

Evidence, Guidelines & Regional Differences

The landmark trials that established modern osteoporosis therapy:^[1][2]

• FIT (Fracture Intervention Trial), Black et al. Lancet 1996 — alendronate in 2027 postmenopausal women with existing vertebral fractures: 47 percent reduction in new vertebral fractures, 51 percent reduction in hip fracture, 28 percent reduction in clinical fractures over 3 years. Established alendronate as first-line antiresorptive.^[3]
• FREEDOM, Cummings et al. NEJM 2009 — denosumab 60 mg SC 6-monthly vs placebo in 7868 postmenopausal women: 68 percent reduction in vertebral fracture, 40 percent reduction in hip fracture, 20 percent reduction in non-vertebral fracture over 3 years. Established denosumab as an alternative antiresorptive.^[4]
• FRAME, Cosman et al. NEJM 2016 — romosozumab vs placebo for 12 months: 73 percent reduction in vertebral fracture at 12 months, 36 percent reduction in clinical fracture. Established romosozumab as a dual anabolic-antiresorptive.^[5]
• ARCH, Saag et al. NEJM 2017 — romosozumab 210 mg monthly for 12 months then alendronate versus alendronate 70 mg weekly alone in 4093 postmenopausal women with osteoporosis and a fragility fracture: 48 percent lower vertebral-fracture risk at 24 months, 27 percent lower clinical-fracture risk, 19 percent lower nonvertebral-fracture risk and 38 percent lower hip-fracture risk.^[6]
• Lyles et al. NEJM 2007 — zoledronic acid after hip fracture — 5 mg IV yearly, first infusion within 90 days of repair: 35 percent reduction in any new clinical fracture and 28 percent reduction in all-cause mortality (median follow-up 1.9 years).^[8]
• Neer et al. NEJM 2001 — teriparatide (PTH 1-34) 20 micrograms SC daily in postmenopausal women with prior vertebral fracture: 65 percent reduction in vertebral fracture, 53 percent reduction in non-vertebral fracture. Established PTH as an anabolic.^[9]
• Kanis et al. Osteoporos Int 2008 (two companion papers) — the FRAX models compute 10-year probabilities of hip fracture and of major osteoporotic fracture from the clinical risk factors with or without femoral-neck BMD; the UK companion paper sets age-dependent intervention thresholds, treating when probability equals that of a same-aged woman with a prior osteoporotic fracture.^[7][10]

^{[1] [26]}

Exam Pearls

^{[29] [27] [10] [1] [4] [14] [30] [28] [8]}

Exam application bank (NEET-PG / INICET)

One-line answer

Osteoporosis is a progressive systemic skeletal disease of low bone mass and microarchitectural deterioration of bone tissue, leading to increased bone fragility and a consequent increase in fracture risk. Operationally (WHO) it is defined by a DEXA T-score of minus 2.5 or less at the femoral neck, total hip or lumbar spine; a low-trauma (fragility) fracture establishes the diagnosis regardless of the T-score. It is the commonest metabolic bone disease of older adults and the underlying cause of most fragility fractures (low-trauma — fall from standing height or less) of the vertebra, hip, distal forearm (Colles) and proximal humerus. Commonest in postmenopausal women and older adults; secondary causes include glucocorticoids, hypogonadism, hyperthyroidism, hyperparathyroidism, CKD, malabsorption, chronic liver disease, smoking, alcohol, low BMI and immobility. Often silent until a fragi

Worked stems (answer without another resource)

Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose/route if drug therapy is standard. ^[1]

Stem 2 — Unstable / complicated. List red flags that force immediate resuscitation, theatre, ICU, antidote, or reperfusion — and what you do in the first 15 minutes. ^[1]

Stem 3 — Atypical group. Elderly, pregnancy, child, or immunocompromised: how presentation and thresholds change. ^[1]

Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each. ^[1]

Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU/ICU/theatre, and what follow-up is mandatory. ^[1]

Rapid viva checklist

1. Definition + classification
2. Pathophysiology chain
3. Bedside signs / criteria
4. Score with exact components (if any)
5. Emergency bundle
6. Definitive therapy with doses
7. Complications of disease and of treatment
8. Special populations
9. Guideline/trial name if classic
10. Three exam traps

Coverage self-check

If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG/INICET questions on Osteoporosis.

References30ShowHide

1. [1]Compston JE, McClung MR, Leslie WD. Osteoporosis Lancet, 2019.PMID 30696576
2. [2]Camacho PM, Petak SM, Binkley N, et al. AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS/AMERICAN COLLEGE OF ENDOCRINOLOGY CLINICAL PRACTICE GUIDELINES FOR THE DIAGNOSIS AND TREATMENT OF POSTMENOPAUSAL OSTEOPOROSIS-2020 UPDATE Endocr Pract, 2020.PMID 32427503
3. [3]Black DM, Cummings SR, Karpf DB, et al. Randomised trial of effect of alendronate on risk of fracture in women with existing vertebral fractures. Fracture Intervention Trial Research Group Lancet, 1996.PMID 8950879
4. [4]Cummings SR, San Martin J, McClung MR, et al. Denosumab for prevention of fractures in postmenopausal women with osteoporosis N Engl J Med, 2009.PMID 19671655
5. [5]Cosman F, Crittenden DB, Adachi JD, et al. Romosozumab Treatment in Postmenopausal Women with Osteoporosis N Engl J Med, 2016.PMID 27641143
6. [6]Saag KG, Petersen J, Brandi ML, et al. Romosozumab or Alendronate for Fracture Prevention in Women with Osteoporosis N Engl J Med, 2017.PMID 28892457
7. [7]Kanis JA, Oden A, Johansson H, Borgstrom F, Strom O, McCloskey E. Case finding for the management of osteoporosis with FRAX--assessment and intervention thresholds for the UK Osteoporos Int, 2008.PMID 18751937
8. [8]Lyles KW, Colón-Emeric CS, Magaziner JS, et al. Zoledronic acid and clinical fractures and mortality after hip fracture N Engl J Med, 2007.PMID 17878149
9. [9]Neer RM, Arnaud CD, Zanchetta JR, et al. Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis N Engl J Med, 2001.PMID 11346808
10. [10]Kanis JA, Johnell O, Oden A, et al. FRAX and the assessment of fracture probability in men and women from the UK Osteoporos Int, 2008.PMID 18292978
11. [11]Boyce BF, Xing L. Functions of RANKL/RANK/OPG in bone modeling and remodeling Arch Biochem Biophys, 2008.PMID 18395508
12. [12]Buckley L, Guyatt G, Fink HA, et al. 2017 American College of Rheumatology Guideline for the Prevention and Treatment of Glucocorticoid-Induced Osteoporosis Arthritis Rheumatol, 2017.PMID 28585373
13. [13]Saag KG, Zanchetta JR, Devogelaer JP, et al. Effects of teriparatide versus alendronate for treating glucocorticoid-induced osteoporosis: thirty-six-month results of a randomized, double-blind, controlled trial Arthritis Rheum, 2009.PMID 19877063
14. [14]Niimi R, Kono T, Nishihara A, et al. Second rebound-associated vertebral fractures after denosumab discontinuation Arch Osteoporos, 2020.PMID 31898803
15. [15]Ettinger B, Black DM, Mitlak BH, et al. Reduction of vertebral fracture risk in postmenopausal women with osteoporosis treated with raloxifene: results from a 3-year randomized clinical trial. Multiple Outcomes of Raloxifene Evaluation (MORE) Investigators JAMA, 1999.PMID 10517716
16. [16]Rossouw JE, Anderson GL, Prentice RL, et al. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial JAMA, 2002.PMID 12117397
17. [17]Harris ST, Watts NB, Genant HK, et al. Effects of risedronate treatment on vertebral and nonvertebral fractures in women with postmenopausal osteoporosis: a randomized controlled trial. Vertebral Efficacy With Risedronate Therapy (VERT) Study Group JAMA, 1999.PMID 10527181
18. [18]Miller PD, McClung MR, Macovei L, et al. Monthly oral ibandronate therapy in postmenopausal osteoporosis: 1-year results from the MOBILE study J Bone Miner Res, 2005.PMID 16007327
19. [19]Blau LA, Hoehns JD. Analgesic efficacy of calcitonin for vertebral fracture pain Ann Pharmacother, 2003.PMID 12659616
20. [20]Truumees E, Hilibrand A, Vaccaro AR. Percutaneous vertebral augmentation Spine J, 2004.PMID 15016401
21. [21]Adler RA, El-Hajj Fuleihan G, Bauer DC, et al. Managing Osteoporosis in Patients on Long-Term Bisphosphonate Treatment: Report of a Task Force of the American Society for Bone and Mineral Research J Bone Miner Res, 2016.PMID 26350171
22. [22]Rajkumar SV, Dimopoulos MA, Palumbo A, et al. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma Lancet Oncol, 2014.PMID 25439696
23. [23]Walker MD, Shane E. Hypercalcemia: A Review JAMA, 2022.PMID 36282253
24. [24]Ralston SH, Langston AL, Reid IR. Pathogenesis and management of Paget's disease of bone Lancet, 2008.PMID 18620951
25. [25]Lambert AS, Zhukouskaya V, Rothenbuhler A, et al. X-linked hypophosphatemia: Management and treatment prospects Joint Bone Spine, 2019.PMID 30711691
26. [26]G R, Gupta A. Vitamin D deficiency in India: prevalence, causalities and interventions Nutrients, 2014.PMID 24566435
27. [27]Sözen T, Özışık L, Başaran NÇ An overview and management of osteoporosis Eur J Rheumatol, 2017.PMID 28293453
28. [28]Schnitzer TJ. Update on alendronate for osteoporosis: once-weekly dosing Expert Opin Pharmacother, 2001.PMID 11585024
29. [29]Faulkner KG, von Stetten E, Miller P. Discordance in patient classification using T-scores J Clin Densitom, 1999.PMID 10548828
30. [30]Zhao JG, Zeng XT, Wang J, et al. Association Between Calcium or Vitamin D Supplementation and Fracture Incidence in Community-Dwelling Older Adults: A Systematic Review and Meta-analysis JAMA, 2017.PMID 29279934