Stress Fracture

See Also

Definitions

Bone Stress Injury (BSI)
1. Accumulation of bone microdamage resulting in a spectrum of overuse injuries
2. Stress Fractures represent 20% of bone stress injuries
3. BSI reflects an injury progression with intervention opportunities before Fracture occurs

Epidemiology

Stress Fracture accounts for up to 20% of sports medicine injuries (varies by sport and cohort)
1. Stress Fracture represents 10-15% of all Running Injury (esp. cross country)
2. Stress Fracture represents up to 20% of injuries in women who are runners or military recruits
3. Stress Fractures occur in up to 10% of military recruits early in basic training (esp. low fitness at entry)
Age
1. Bimodal distribution (age <20 years and age >40 years)
Gender Relative Risks
1. Women > Men
  1. Relative Risk = 3.5 overall (including female military recruits and athletes)
2. White males > Black males
  1. Relative Risk = 4.7
3. White females > Black females
  1. Relative Risk = 8.5

Mechanisms

Bone remodeling is triggered by microinjury
1. Osteoclasts remove damaged bone and Osteoblasts lay down new bone in its place
2. Repeated microinjury results in an imbalance between load-induced microinjury and repair
  1. Microdamage accumulates when rate of damage exceeds rate of repair
  2. Osteoclast removal of bone is not matched by sufficient Osteoblast activity
3. Injuries progress from bone stress reaction, to Stress Fracture and to complete Fracture
  1. Stress reactions have increased bone turnover (marrow edema on MRI)
  2. Stress Fractures demonstrate a Fracture line
Contributing Factors
1. Weight bearing
2. Muscle forces
  1. Muscle Strength increases faster than bone strength
3. Muscle Fatigue

Risk factors

Repetitive activity in Sports and Training
1. Military recruits
2. Distance Running (e.g. cross country)
  1. Mileage >25 miles per week (esp. >40 miles/week)
  2. Running on irregular or banked surfaces
3. Track and Field
4. Basketball
5. Soccer
6. Dance
7. Gymnastics
Increases in intensity, frequency, and loading
1. Too fast
2. Too far
  1. Increased duration of high impact activity is correlated with an increased Stress Fracture risk
    1. Field (2011) Arch Pediatr Adolesc Med 165(8): 723-8 [PubMed]
3. Too soon
  1. Stress Fracture risk increases in the first 2 weeks of increasing training intensity
  2. Insufficient recovery after Exercise
  3. Low fitness level before starting a new Exercise program
Biomechanical forces (esp. Running)
1. Over pronators or Supinators
2. Rear foot eversion during stance phase
3. Excessive hip adduction
4. Hallux Valgus
5. Genu Varum or genu valgus
6. Increased Q Angle of the Knee
7. High Longitudinal Arch
8. Leg Length Discrepancy
9. External hip rotation
10. Changes in foot gear or training surface
11. Decreased lower extremity Muscle mass
12. Muscle Fatigue
13. Cowan (1996) Med Sci Sports Exerc 28(8): 945-52 [PubMed]
14. McCormick (2012) Clin Sports Med 31:291-306 [PubMed]
15. Gallo (2012) Sports Health 4(6): 485-95 [PubMed]
Systemic Diseases that weaken bone
1. Osteoporosis (Female Athlete Triad, RED-S)
2. Rheumatoid Arthritis
3. Systemic Lupus Erythematosus
4. Osteoarthritis
5. Pyrophosphate Arthropathy
6. Renal Disease
7. Joint Replacement
Other Associated risk factors
1. Tobacco Abuse
2. Alcohol >10 drinks per week
3. NSAID longterm use
4. Weight extremes (BMI <19 or >30 kg/m2)
5. Female Athlete Triad (Relative Energy Deficiency in Sport)
6. Female Gender
  1. Female runners are twice as likely as male runners to sustain Stress Fractures
  2. Highest risk among female runners with lower BMI, increased foot pronation and wider Pelvis
  3. Pujalte (2014) Med Clin North Am 98(3): 851-68 [PubMed]
7. Nutritional deficiency
  1. Eating Disorder or dieting
  2. Inadequate Dietary Calcium
  3. Inadequate Vitamin D (Vitamin D Deficiency)
  4. Low Fat Diet
  5. Nieves (2010) PM R 2(8): 740-50 [PubMed]

Pathophysiology
Distribution

Sites of Stress Fracture are dependent on causative activity
Common Stress Fracture Sites
1. Tibia Stress Fracture (23-50% of Stress Fractures among athletes)
2. Metatarsal Stress Fracture (16% of Stress Fractures)
3. Fibula Stress Fracture (15% of Stress Fractures)
4. Tarsal Navicular Stress Fracture
5. Calcaneal Stress Fracture
6. Medial Malleolus Stress Fracture
7. Femoral Neck Stress Fracture (6%)
8. Femoral Shaft Stress Fracture
9. Pubic Ramus Stress Fracture
10. Pelvic Stress Fracture (1-2%, almost exclusively in women)
11. Lumbar Stress Fracture
12. Coracoid process Stress Fracture
13. Humerus Stress Fracture
14. Olecranon Stress Fracture
Most common Stress Fracture sites in high school and college athletes
1. Lower leg (32 to 40%)
  1. Tibia Stress Fracture
  2. Fibula Stress Fracture
2. Foot (35 to 38%)
  1. Metatarsal Stress Fracture
3. Lumbar Spine or Pelvis (12 to 15%)
  1. Pelvic Stress Fracture
  2. Pubic Ramus Stress Fracture
  3. Lumbar Stress Fracture
4. Femur (7%)
  1. Femoral Neck Stress Fracture
  2. Femoral Shaft Stress Fracture
5. References
  1. Changstrom (2015) Am J Sports Med 43(1):26-33 +PMID: 25480834 [PubMed]
  2. Rizzone (2017) J Athl Train 52(10):966-75 +PMID: 28937802 [PubMed]
Stress Fracture by complication risk
1. High complication risk sites
  1. Anterior Shaft Tibia Stress Fracture
  2. Tarsal Navicular Stress Fracture
  3. Femoral Neck Stress Fracture (esp. tension sided, superior aspect)
    1. Often requires prophylactic surgery (even low-grade Stress Fractures)
  4. Base of fifth Metatarsal Stress Fracture (proximal diaphysis)
  5. Base of second Metatarsal Stress Fracture
  6. Medial Malleolus Stress Fracture
  7. Talus Stress Fracture
  8. Great toe Sesamoid Fracture
  9. Patella Stress Fracture
2. Low complication risk sites
  1. Posteromedial Shaft Tibia Stress Fracture
  2. Fibula Stress Fracture
  3. Femoral Shaft Stress Fracture

Symptoms

Deep ache following rapid training change (too fast, too far, too soon)
Pain progression
1. Start: Pain after activity
2. Next: Pain with activity
3. Next: Pain with walking (at presentation in 81% of patients)
4. Last: Pain at rest
Night pain rarely occurs
1. Consider another diagnosis (e.g. malignancy)

Signs

Fracture site intense localized pain
1. Tenderness to palpation (present in most cases)
2. Edema at Fracture site may be present
3. Compression induces pain
4. Percussion of bone distant from symptomatic site (e.g. heel percussion test)
5. Vibrating tuning fork (128 Hz) at suspected site
  1. Mediocre Test Sensitivity and Specificity
  2. Lesho (1997) Mil Med 162(12): 802-3 [PubMed]
Specific Tests for leg or pelvis Stress Fracture
1. Fulcrum Test
2. Hop Test
  1. Poor Specificity (common finding in Shin Splints)
  2. Batt (1998) Med Sci Sports Exerc 30(11): 1564-71 [PubMed]

Differential Diagnosis

Chronic Musculoskeletal Disorders
1. Tendinopathy or Muscle Strain
2. Ligamentous Injury
3. Chronic Compartment Syndrome
4. Osteoarthritis
5. Hypertrophic Pulmonary Osteoarthropathy
Nerve Compression Syndromes
1. Tarsal Tunnel Syndrome
2. Carpal Tunnel Syndrome
3. Ulnar Tunnel Syndrome
4. Herniated Intervertebral Disc
Infections
1. Chronic or Subacute Osteomyelitis
Bone Neoplasm
1. Primary Benign
2. Primary Malignant
  1. Osteosarcoma
  2. Ewing Sarcoma
3. Metastatic Neoplasm to bone
  1. Breast Cancer
  2. Prostate Cancer

Labs

Serum 25-HydroxyVitamin D Level
1. Consider in Bone Stress Injury
2. However interpretation may be difficult (i.e. what is considered normal)

Imaging

Overall imaging approach (preferred)
1. Step 1: XRay negative and Stress Fracture suspicion persists (while restricting activity)
2. Step 2: Repeat XRay in 2-3 weeks is negative and Stress Fracture suspicion persists (while restricting activity)
3. Step 3: Obtain MRI (preferred) or bone scan
  1. May perform earlier in moderate-severe symptoms, high risk site or unable to reduce activity
Imaging modalities
1. Stress Fracture XRay
2. Stress Fracture Bone Scan
3. Stress Fracture CT
4. Stress Fracture MRI
  1. Preferred second-line study after XRay
  2. Identifies marrow edema (stress reaction) and subtle Fracture lines
  3. Evaluates regional soft tissue
5. Point of Care Ultrasound (POCUS)
  1. Findings suggestive of Bone Stress Injury (operator dependent)
    1. Subcutaneous edema
    2. Periosteal thickening
    3. Cortical Bone irregularity
    4. Periosteal Callus
    5. Local hyperemia (doppler)
  2. Ultrasound is being investigated for specific Stress Fracture sites (e.g. Metatarsal Stress Fracture)
    1. Banal (2009) J Rheumatol 36(8): 1715-9 [PubMed]

Grading
Bone Stress Injury

Grade 1: Stress Reaction (low-grade)
1. XRay normal
2. MRI with periosteal edema (T2) and normal marrow (T1)
3. Bone scan with small, poorly defined lesion and cortex with mild activity increase
Grade 2: Stress Reaction (low-grade)
1. XRay normal
2. MRI with moderate marrow and periosteal edema (T2) and normal marrow (T1)
3. Bone scan with increased well-defined, elongated lesion and cortex with moderate activity increase
Grade 3: Stress Reaction (high grade)
1. XRay normal, periosteal reaction or distinct Fracture line
2. MRI with severe marrow and periosteal edema (T1 and T2)
3. Bone scan with wide fusiform lesion and corticomedullary region with high activity increase
Grade 4: Stress Fracture
1. XRay with periosteal reaction or distinct Fracture line
2. MRI with Fracture line as well as severe marrow and periosteal edema (T1 and T2)
3. Bone scan with wide extensive lesion and transcorticomedullary region with high activity increase

Management

Reevaluate patients every 1 to 3 weeks (with imaging as needed)
Analgesia
1. Acetaminophen is preferred over NSAIDS (which may delay bone healing)
Nutrition
1. See Relative Energy Deficiency in Sport (RED-S)
2. Adequate nutrition to support healing and activity
3. Consider Vitamin D Supplementation in patients at higher risk of deficiency
Immobilization
1. Short-leg Casting or CAM-Walker Indications
  1. Non-compliance
  2. High-risk for non-union
    1. Navicular Stress Fracture
    2. Metatarsal Stress Fracture
2. Pneumatic brace (Air cast)
  1. Support results in quicker recovery and less pain
  2. Indicated in tibial and fibular Stress Fractures
Activity Restriction (protocol assumes lower risk Bone Stress Injury)
1. Relative Rest for 4-7 weeks (may require up to 3 months)
2. Activity should be pain-free only
  1. Start with crutch walking only (non-weight bearing on affected limb)
  2. Attempt to walk without Crutches for 2 minutes at 2 MPH each day (and otherwise Crutches only)
  3. Advance to 5 min, 10 min and 15 min without Crutches on subsequent days as tolerated
  4. Advance to pain free ambulation once ambulating without Crutches for 15 min/day (pain free)
3. Reduce Stress Fracture risk
4. Non-weight bearing until pain free while walking
  1. Tibia Stress Fracture
  2. Femoral Stress Fracture
Cross training
1. Consider formal rehabilitation program with physical therapy for strength and Stretching
2. Goals
  1. Cardiovascular conditioning
  2. Flexibility
  3. Proprioception
  4. Strength
3. Activities
  1. Swimming
  2. Pool Running with float vest or antigravity treadmill Running
  3. Biking (or Exercise bike)
  4. Stair climbing machines or elliptical machine (later stages)
  5. Rowing Machine
4. Return to Running Protocol (example)
  1. Perform chosen cross-training activity 30 min/session, 3 times weekly as tolerated
  2. Once pain free (or <=3/10) after 3 sessions, may advance to walk-to-Running program
    1. Phase 1: Hopping
    2. Phase 2: Walk to jog intervals (non-consecutive days)
    3. Phase 3: Return to 2 to 3 Running sessions/week (gradual return while pain-free)
  3. Additional progression specific to patient goals (consider sports medicine or physical therapy guidance)
    1. Progressive sport specific movement training
    2. High impact training
    3. Full return to sport and normal activity clearance after completing specific targets
  4. References
    1. Schroeder (2024) Am Fam Physician 110(6): 592-600 [PubMed]
5. Progressive return to primary activity Precautions
  1. Many low risk Stress Fractures (e.g. tibia, fibula) require 4-8 weeks of rest prior to resuming Running
    1. Some Stress Fractures (e.g. posteromedial tibia, Sacrum or Pelvis) require 12 weeks of rest
  2. Pain free ambulation and cross training for at least 2 weeks, before reinitiating Running
    1. Start at 30-50% of preinjury intensity and duration
    2. Gradually increase intensity and duration by no more than 10% per week
    3. Pain with activity or after activity should signal need to rest or back-off intensity and duration
Surgery or Sports Medicine Referral Indications
1. Indications
  1. High Risk Stress Fracture Sites including non-union
  2. Non-healing Fractures
  3. Persistent symptoms at 3 months
2. Specific high risk sites
  1. Tarsal Navicular Stress Fracture
  2. Proximal anterior Tibia Stress Fracture
  3. Base of fifth Metatarsal Stress Fracture (proximal diaphysis)
  4. Base of second Metatarsal Stress Fracture
  5. Femoral Neck Stress Fracture
  6. Medial Malleolus Stress Fracture
  7. Talus Stress Fracture
  8. Great toe Sesamoid Fracture
  9. Patella Stress Fracture
3. Modifying factors
  1. High risk Stress Fracture sites have high complication rates
    1. Malunion
    2. Progression to complete Fracture
    3. Avascular necrosis
    4. Arthritic changes
  2. High risk Stress Fracture sites with non-displaced, low-grade MRI may respond to conservative therapy
    1. Consider 6-8 weeks of immobilization and non-weight bearing
Measures without enough evidence to recommend
1. Extracorporeal Shock Wave Therapy
2. Low Intensity pulsed Ultrasound
3. Photo-biomodulation (low level Light Therapy)
4. Bone Marrow Aspirate concentrate injections
5. Platelet rich plasma injections
6. Pulsed recombinant human Parathyroid Hormone
7. Electromagnetic field devices (Questionable efficacy, High cost)

Complications

Stress Fracture or Complete Fracture (in contrast to low grade Bone Stress Injury)
Delayed union or nonunion
Avascular necrosis

Prevention

Do not increase Exercise intensity >10% per week
Maintain fitness starting in childhood with regular and varied Physical Activity
Stretch and warm-up before Exercise
Choose level Running surfaces
Shoes should be light weight and in good condition
Consider Orthotics for biomechanical factor correction
Shock-absorbing insoles may be beneficial
Osteoporosis Prevention (unclear efficacy)
1. Consider Calcium supplement 1000 mg orally daily
2. Consider Vitamin D 800 IU orally daily
Military recruit shoes
1. Light shoes with small heel to toe drop, wider toe box
2. Kasper (2023) Transl J Am Coll Sports Med 8(4): 1-7 [PubMed]

Reference

Simmons (1997) AAFP Sports Med Review
Titchner, Morris and Davenport (2021) Crit Dec Emerg Med 35(5): 17-23
Buckwalter (1997) Am Fam Physician, 56(1):175-182 [PubMed]
Patel (2011) Am Fam Physician 83(1): 39-46 [PubMed]
Sanderlin (2003) Am Fam Physician 68:1527-32 [PubMed]
Schroeder (2024) Am Fam Physician 110(6): 592-600 [PubMed]
Warden (2014) J Orthop Sports Phys Ther 44(10): 749-65 [PubMed]