Description

• Stress fractures are overuse injuries caused by cumulative microdamage from repetitive bone loading.
• Stress fractures occur in different situations:
  • Fatigue fracture: abnormal repetitive stress applied to normal bone (e.g., young college athletes or new military recruits with increased physical activity demands and inadequate conditioning); common sites include tibia, fibula, metatarsals, femoral neck, and navicular.
  • Insufficiency fracture: normal stress applied to structurally abnormal bone (e.g., femoral neck fracture in osteopenic bone, metabolic bone disease); common sites include spine, sacrum, femoral neck, and medial femoral condyle.
  • Combination fracture: abnormal stress applied to abnormal bone (e.g., female long-distance runners with premature osteoporosis from athletic triad)
• Weight-bearing bones of the lower extremity are most commonly affected at the following sites:
  • Tibia/fibula (most common)
  • Metatarsals (second most)
  • Navicular
  • Femoral neck
  • Pars interarticularis
• High-risk stress fractures occur in zones of tension or areas with poor blood supply and are more likely to result in fracture displacement and/or nonunion. High-risk sites include the following:
  • Femoral neck
  • Anterior tibial diaphysis
  • Sesamoids
  • Pars interarticularis of lumbar spine (L4, L5)
  • 5th metatarsal at metaphyseal–diaphyseal junction
  • Proximal 2nd metatarsal
  • Medial malleolus
  • Tarsal navicular
  • Patella
  • Talar neck
• Synonym(s): march fracture; fatigue fracture

Epidemiology

Incidence

• Greatest incidence in 15- to 27-year-olds
• Females > males
• Accounts for up to 20% of visits to sports medicine and orthopedic clinics

Prevalence

• Lifetime athletic stress fracture is 10% (1).
• Affects up to 6.9% of male and 21.0% of female military members

Etiology and Pathophysiology

• Bone is dynamic and constantly remodeling in response to applied physiologic stress.
• Repetitive loading or overuse causes microfractures that fail to heal due to imbalance between bone resorption and bone formation.
• If microdamage accumulates in excess of reparation, bony fatigue leads to stress fracture.

Risk Factors

• Intrinsic
  • Females are at 2.3 times higher risk than males.
  • Female athlete triad
  • Small tibial width
  • Later menarche, amenorrhea, or irregular menses
  • History of stress fracture
  • History of osteoporosis, osteomalacia, rheumatoid arthritis, prolonged corticosteroid therapy
  • BMI <19 kg/m²
  • Skeletal malalignment: pes cavus/planus, leg length discrepancies, excessive forefoot varus, tarsal coalitions, prominent posterior calcaneal process, tight heel cords
  • Biomechanical factors such as increased vertical loading rate (e.g., heel-to-toe running instead of forefoot striking)
• Extrinsic
  • High-risk exercises—track and field, cross country
  • Training regimen—running >20 miles/week or training >5 hr/day
  • Nutritional—inadequate caloric intake or history of eating disorder
  • Chronic low vitamin D
  • Rapid increase in mileage, running pace, or training volume
  • Inappropriate footwear
  • Hard training/running surface
  • Inadequate recovery or rest and training with fatigued muscle
  • Lifestyle: high alcohol intake or smoking
  • Meds: glucocorticoids, anticonvulsants, antidepressants, depot-medroxyprogesterone acetate (DMPA), methotrexate, antiretrovirals, chronic cannabis use, >5 years of bisphosphonate use

General Prevention

• Prevention is the key especially in adolescent athletes (1).
• Graduated increments in training load intensity: no >10% per week
• Optimize energy balance.
• Diversify sports participation (minimizing sports specialization).
• Reduce intensity and duration of activity if new-onset pain.
• Proper footwear (Athletes should have a gait analysis prior to training.)
• Increasing dynamic physical activity (jumping; plyometric training) increases bone density and resistance to mechanical stress.
• Decrease vertical loading rate either by switching to forefoot strike running or (if continuing with heel-to-toe strike) by using a heel pad insert.
• Vitamin D supplementation (800 IU/day) in combination with calcium (2,000 mg/day)

Commonly Associated Conditions

• Osteoporosis/osteopenia
• Female athlete triad
• Metabolic bone disorders