Osteoporosis

Overview – Osteoporosis

Osteoporosis is a systemic skeletal disorder characterised by reduced bone mass and microarchitectural deterioration, leading to increased bone fragility and fracture risk. Defined by the World Health Organization as a bone mineral density (BMD) T-score of less than -2.5 standard deviations below the mean, osteoporosis primarily affects older adults—particularly postmenopausal women. Its complications, such as vertebral and neck of femur fractures, contribute significantly to morbidity and mortality in ageing populations. This page outlines the types, pathophysiology, diagnosis, and management of osteoporosis.

Definition

• Osteoporosis: BMD >2.5 standard deviations below the young-adult mean (T-score ≤ -2.5)
• Osteopenia: BMD between -1.0 and -2.5 SDs below the young-adult mean

Aetiology

Primary Osteoporosis

• Type 1 – Postmenopausal
  • ↓ Oestrogen → ↑ Osteoclast activity
  • Common fracture sites: vertebrae, neck of femur
  • Affects females only
• Type 2 – Senile
  • ↓ Osteoblast activity due to ageing
  • Affects both sexes, involves all bones

Secondary Osteoporosis

• Endocrine: Cushing’s, ↑PTH, hypo-/hyperthyroidism, diabetes, Addison’s, acromegaly
• Reproductive: Pregnancy & lactation
• Haematological: Multiple myeloma
• Nutritional: Malnutrition, malabsorption
• Medications: Corticosteroids, chemotherapy
• Lifestyle: Alcohol excess, immobility

Pathogenesis

• Imbalance: ↑ Osteoclast activity vs. ↓ Osteoblast function
  → Increased bone resorption
  → Loss of bone mass and structural integrity
  → “Porous bones” on histology

Morphology

• Microscopy: Thin, sparse trabeculae
• Macroscopic: Fragile bone with increased fracture risk

Clinical Features

• Often asymptomatic until fracture occurs
• Fragility fractures (minimal trauma) are hallmark
  • Common sites: vertebrae, hip, wrist
  • RR of fracture doubles for every 1.0 SD ↓ in BMD
• Vertebral compression fractures: May cause spinal cord compression or cauda equina syndrome

Investigations

Imaging

• Plain X-ray: Often normal in early stages
• DXA scan (Dual-energy X-ray Absorptiometry)
  • Essential: Lumbar spine + hip
  • Optional: Forearm

Blood Tests (for secondary causes)

• ESR → Rule out myeloma
• Vitamin D → Deficiency assessment
• PTH → Hyperparathyroidism
• TSH → Hyperthyroidism

Management

Pharmacological

• Bisphosphonates (Alendronate, Risedronate) – Inhibit osteoclasts
• Strontium ranelate – Promotes calcium deposition, reduces resorption
• Hormonal (in perimenopausal/postmenopausal women)
  • SERMs (e.g., Raloxifene)
  • HRT

Supplements

• Calcium and Vitamin D (OTC)

Lifestyle and Occupational Measures

• Reduce fall risk
• Weight-bearing exercise to maintain bone mass

Summary – Osteoporosis

Osteoporosis is a common, silent metabolic bone disease defined by reduced bone mineral density and increased risk of fragility fractures. It can be primary (postmenopausal or senile) or secondary to numerous systemic conditions and medications. Diagnosis relies heavily on DXA scanning and T-/Z-score interpretation. Treatment includes bisphosphonates, supplements, and fall prevention strategies. For more, visit our Musculoskeletal Overview page.