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Sports physiotherapy · Sports medicine

Stress fracture in the athlete 2026 update

In brief

A stress fracture (bone stress injury) is a continuum of injury running from an oedematous reaction to a cortical fracture, caused by an imbalance between microdamage and bone repair under excessive cyclic loading in the athlete. The pain is insidious and localised, at first only on exercise; the tibia and the metatarsals dominate the distribution. The main modifiable cause is training error, the major systemic cause is REDs (relative energy deficiency). MRI is the reference investigation. Management rests on pain-guided load modification and cross-training, not on absolute rest. These injuries account for 15 to 20 % of musculoskeletal injuries in runners.

Clinical synthesis based on the most recent international consensus statements: the 2025 BSI Delphi, IOC REDs 2023, Nature Reviews 2022, and the 2021-2024 JOSPT and BJSM meta-analyses.

MRI diagnosis REDs & female athletes Return to sport Evidence-based
15-20%
MSK injuries in runners
Hoenig 2022 · Nat Rev Dis Primers
×2-4
BSI risk in women vs men
Tenforde 2024 · OJSM
>90%
Return to sport after management
Hoenig 2023 · BJSM meta-analysis

Clinical summary

  • The bone stress injury (BSI) is a continuum of injury running from an oedematous reaction to a cortical fracture, caused by an imbalance between microdamage and the bone's capacity to repair.
  • It accounts for 15-20 % of musculoskeletal injuries in runners, with a 2-4× higher risk in women. The tibia and the metatarsals dominate the anatomical distribution.
  • The main modifiable cause is training error (volume or intensity increased too quickly); the major systemic cause is REDs (Relative Energy Deficiency in Sport).
  • Female athletes have a 2- to 4-fold higher risk of BSI; amenorrhoea alone multiplies the risk by 4.7. REDs affects men too (LEA prevalence around 49 %).
  • MRI is the reference investigation (Se ~100 %, Sp 86 %). The initial radiograph is falsely reassuring in 70-90 % of early cases.
  • Stratification into high risk vs low risk (femoral neck, navicular, anterior tibia, 5th MT vs posteromedial tibia, fibula) governs the whole of management.
  • The Fredericson MRI grade is predictive of the time to return to sport (42 days for grade 1 to 98 days for grade 4, Hoenig 2022 meta-analysis).
  • Treatment rests on pain-guided load modification and cross-training, not on absolute rest. Return to sport is criteria-based, not calendar-based.
  • The acute-to-chronic workload ratio (ACWR) should stay in the 0.8-1.3 sweet spot; a ratio ≥ 1.5 multiplies injury risk by 2-4.
  • Shockwave therapy (ESWT) has moderate efficacy for delayed union; LIPUS and manual therapy have very limited evidence in acute BSI.
  • Preventing recurrence (20-30 % in runners) means correcting the systemic causes: load, REDs, biomechanics, vitamin D, calcium.
  • The IOC's 2023 CAT2 stratifies REDs into 4 traffic lights (green/yellow/amber/red) with an associated course of action.
  • BSIs can mimic other conditions: sciatica (sacral BSI), psoas tendinopathy (femoral neck BSI), medial tibial stress syndrome.
  • Multiple or bilateral BSIs call for a systematic REDs work-up : menstrual cycles, DEXA, vitamin D, ferritin, endocrine panel.
  • Referral to the sports physician or the orthopaedic surgeon is urgent for high-risk sites (risk of non-union, necrosis, displacement).

Contents

  1. What are the fundamentals to know about stress fracture in the athlete?
    1. Definition, epidemiology and risk factors
    2. Pathophysiology and natural course of BSI
  2. Why do female athletes and REDs call for particular vigilance?
    1. Physiological specifics and the ×2-4 risk
    2. The REDs syndrome: definition, screening, CAT2
    3. Triad Cumulative Risk Assessment and stratification
  3. How do you diagnose a stress fracture with certainty?
    1. Targeted history-taking and red flags
    2. Clinical examination and differential diagnosis
    3. Imaging: why and how to classify?
    4. Diagnostic decision algorithm
  4. What is the most effective treatment strategy?
    1. Hierarchy of recommended interventions
    2. Progressive load and the acute-to-chronic ratio
    3. Adjunctive modalities and GRADE level of evidence
  5. How do you prevent recurrence and plan the return to sport?
    1. Self-management and therapeutic education
    2. Performance-based return-to-sport criteria
  6. What do the published clinical cases teach us?
    1. Case 1: female runner, buttock pain simulating sciatica
    2. Case 2: elite female runner, bilateral femoral neck fractures
    3. Case 3: a series of 62 navicular fractures
  7. How do you apply these recommendations in practice?
    1. When and to which professionals should you refer?
    2. Measuring outcomes and overcoming barriers to implementation

What are the fundamentals to know about stress fracture in the athlete?

In this chapter: the contemporary definition of bone stress injury (BSI) as a continuum, consolidated epidemiology (15-20 % of MSK injuries in runners), extrinsic risk factors (training load) and intrinsic ones (REDs, BMD), the pathophysiology of bone remodelling and the natural course.
The term bone stress injury (BSI) now covers the continuum once split into “stress reaction”, “fatigue fracture” and “complete fracture”. This consensus terminology, adopted by Nature Reviews Disease Primers in 2022 and by the international Delphi in 2025, better reflects the progressive nature of the condition.¹٬¹¹ 🦴

Definition, epidemiology and risk factors

A BSI results from an accumulation of bone microdamage when cyclic mechanical stress exceeds the capacity of bone tissue to adapt and repair. The spectrum runs from isolated marrow oedema (visible only on MRI) to a complete displaced cortical fracture.¹ Epidemiologically, BSIs account for 15 to 20 % of musculoskeletal injuries in runners, with up to 13 % of female athletes reporting a previous episode in some cohorts.² The sports most at risk are distance running, triathlon, classical ballet, basketball, and military recruits in basic training.¹
15-20 %MSK injuries in runners
×2-4Risk in women vs men
~50 %BSI in the tibia
20-30 %Recurrence rate
The risk factors fall classically into two registers:
  • Extrinsic factors (modifiable): l'training error remains the dominant trigger, with a rapid increase in volume, intensity or frequency, a change of surface (road → track), or unsuitable equipment.⁴
  • Intrinsic factors: female sex, a personal history of BSI (×3 risk of recurrence), low BMD, altered running biomechanics, vitamin D and calcium deficiency.¹⁰
One intrinsic factor deserves particular attention: REDs (Relative Energy Deficiency in Sport). This syndrome, redefined by the IOC's international consensus in 2023, covers the consequences of low energy availability for bone, hormonal, metabolic and mental health, and affects both sexes.⁵

📊 Anatomical distribution of stress fractures in the athlete

Synthesis of the literature (Matheson 1987, Hoenig 2022, Pegrum 2012)

Anatomical distribution of stress fractures in the athlete Site % of cases Tibia 23-49 % Metatarsals 12-17 % Tarsal navicular ★ 10-18 % Fibula 8-15 % Pelvis / sacrum 6-9 % Femoral neck ★ 2-8 % Ribs / other 3-14 % ★ High-risk sites, a diagnostic emergency because of the risk of non-union

Sources: Hoenig 2022 (Nat Rev Dis Primers), Pegrum 2012 (BMJ).¹٬¹⁶

Pathophysiology and natural course of BSI

Bone is a living tissue in constant remodelling, through the coupling of osteoclasts (resorption) and osteoblasts (formation).¹⁵ Under normal cyclic loading, this remodelling adapts bone tissue to the stresses placed on it (Wolff's law). Under excessive cyclic loading with insufficient recovery between bouts, osteoclastic resorption transiently outpaces formation, creating resorption cavities that locally weaken the cortex and increase porosity.¹ If loading continues without allowing consolidation, the microdamage coalesces into a cortical fracture line, and ultimately a complete fracture.
A stress fracture is not an acute event: it is the meeting of excessive cyclic load with a bone that has not had time to repair. Understanding that equation is already half of preventing recurrence.

Key points

  • The BSI is a continuum, a term to prefer to “fatigue fracture”.
  • Training error (volume or intensity increased too quickly) remains the number one modifiable trigger.
  • The REDs is the major systemic factor, affecting both sexes.
  • The tibia and the metatarsals dominate the distribution; femoral neck and navicular are high risk.
  • The pathophysiology rests on an imbalance between bone resorption and formation under excessive load.
Bibliography
  1. Hoenig T, Ackerman KE, Beck BR, Bouxsein ML, Burr DB, Hollander K, et al. Bone stress injuries. Nat Rev Dis Primers. 2022;8(1):26. PMID 35484131.
  2. Warden SJ, Davis IS, Fredericson M. Management and prevention of bone stress injuries in long-distance runners. J Orthop Sports Phys Ther. 2014;44(10):749-65. PMID 25103133.
  3. Wright AA, Taylor JB, Ford KR, Siska L, Smoliga JM. Risk factors associated with lower extremity stress fractures in runners: a systematic review with meta-analysis. Br J Sports Med. 2015;49(23):1517-23. PMID 26582192.
  4. Warden SJ, Edwards WB, Willy RW. Preventing bone stress injuries in runners with optimal workload. Curr Osteoporos Rep. 2021;19(3):298-307. PMID 33635519.
  5. Mountjoy M, Ackerman KE, Bailey DM, Burke LM, Constantini N, Hackney AC, et al. 2023 IOC consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073-1097. PMID 37752011.
  6. Hoenig T, Tenforde AS, Strahl A, Rolvien T, Hollander K. Does MRI Grading Correlate With Return to Sports After Bone Stress Injuries? A Systematic Review and Meta-analysis. Am J Sports Med. 2022;50(3):834-844. PMID 33720786.
  7. McInnis KC, Ramey LN. High-Risk Stress Fractures: Diagnosis and Management. PM R. 2016;8(3 Suppl):S113-S124. PMID 26972260.
  8. Hoenig T, Eissele J, Strahl A, Popp KL, Hollander K, Warden SJ, et al. Return to sport following low-risk and high-risk bone stress injuries: a systematic review and meta-analysis. Br J Sports Med. 2023;57(7):427-432. DOI 10.1136/bjsports-2022-106328.
  9. Patel DS, Roth M, Kapil N. Stress fractures: diagnosis, treatment, and prevention. Am Fam Physician. 2011;83(1):39-46. PMID 21888126.
  10. Tenforde AS, Ackerman KE, Bouxsein ML, et al. Factors Associated With High-Risk and Low-Risk Bone Stress Injury in Female Runners. Orthop J Sports Med. 2024;12(5):23259671241246227. PMID 38779133.
  11. Hoenig T, Hollander K, Ackerman KE, et al. International Delphi consensus on bone stress injuries in athletes. Br J Sports Med. 2025;59(2):85-94. PMID 39638438.
  12. Sale C, Elliott-Sale KJ. Nutrition and Athlete Bone Health. Sports Med. 2019;49(Suppl 2):139-151. PMID 31696454.
  13. Tenforde AS, Kraus E, Fredericson M. Bone Stress Injuries in Runners. Phys Med Rehabil Clin N Am. 2016;27(1):139-149. PMID 26616181.
  14. Nattiv A, Kennedy G, Barrack MT, et al. Correlation of MRI Grading of Bone Stress Injuries With Clinical Risk Factors and Return to Play. Am J Sports Med. 2013;41(8):1930-1941. PMID 23825184.
  15. Robling AG, Castillo AB, Turner CH. Biomechanical and molecular regulation of bone remodeling. Annu Rev Biomed Eng. 2006;8:455-98. PMID 16834564.
  16. Pegrum J, Crisp T, Padhiar N. Diagnosis and management of bone stress injuries of the lower limb in athletes. BMJ. 2012;344:e2511. PMID 22532009.

Why do female athletes and REDs call for particular vigilance?

In this chapter: the physiological specifics behind the ×2-4 risk in women, the REDs syndrome (Relative Energy Deficiency in Sport) redefined by the IOC in 2023, the clinical stratification tools (Triad Cumulative Risk Assessment, the CAT2 traffic light), and the specifics in men (LEA prevalence around 49 %).
Female athletes have a risk of bone stress injury 2 to 4 times higher than men in the same disciplines.¹⁰ This over-representation is not fatalistic biology: it is largely explained by a modifiable and under-diagnosed systemic factor, REDs (Relative Energy Deficiency in Sport). 🚺

Physiological specifics and the ×2-4 risk

Several mechanisms converge to explain female bone vulnerability in sport:
  • A lower peak bone mass reached earlier (around 18-20 years in women vs 20-25 in men).¹
  • Hormonal dependence of bone formation: oestradiol is protective, and any disturbance of the hypothalamic-pituitary-gonadal axis directly affects BMD.²
  • Bone geometry: female femoral and tibial shafts are on average narrower, with a lower section modulus.³
  • Sociocultural pressures that are specific (appearance, weight, dietary restriction) and more frequent in certain at-risk disciplines (dance, gymnastics, distance running).⁴

📊 Relative risk of BSI by factor: synthesis of cohorts

Cumulative BSI risk factors in the female athlete (Tenforde 2017, 2024; Barrack 2014)

Cumulative BSI risk factors in the female athlete Risk factor Odds ratio / relative risk 1× 2× 3× 4× 5×+ Female sex (vs male) 2-4× Amenorrhoea / oligomenorrhoea OR 4.7 Personal history of BSI ~3× BMD Z-score < -1.0 2-3× High Triad Risk Score (≥6 pts) ~4× Moderate Triad Risk Score (2-5) 2× BMI < 18.5 kg/m² 2,5-3,5× 25(OH)D < 50 nmol/L ~1,2×

Sources: Tenforde 2017 AJSM, Tenforde 2024 OJSM, Barrack 2014, Mountjoy 2023.⁵٬⁶٬⁷

The REDs syndrome: definition, screening, CAT2

The concept of REDs is defined as the whole set of harmful consequences of low energy availability (LEA) for health and sporting performance. It was redefined in 2023 by the IOC as a multisystem syndrome affecting both sexes, and no longer as a “female triad”.⁴ Energy availability (EA) is calculated as follows:

EA = (energy intake − exercise energy expenditure) / fat-free mass (kg FFM)

⚡ The spectrum of energy availability (EA)

Severe LEA < 30 kcal/kg FFM/day disrupts the hypothalamic-pituitary-gonadal axis within 4-5 days

EA spectrum optimal suboptimal severe LEA 30 kcal/kg FFM 45 kcal/kg FFM Severe LEA Suboptimal Optimal EA 0 60+ BSI risk ↑↑↑ BSI risk ↑ BSI risk minimal

Adapted from Loucks 2011 (J Sports Sci) and IOC 2023 (Mountjoy).⁴٬⁸

The CAT2 (REDs Clinical Assessment Tool version 2, IOC 2023) offers a four-level stratification on an “enriched traffic light” system:⁹
LevelClinical indicatorsCourse of action
🟢 GREENNo or few REDs indicatorsFull participation in sport
🟡 YELLOWEarly indicators (moderate LEA, slightly irregular cycles)Continuous monitoring, nutritional advice
🟠 AMBERSeveral clinical indicators (amenorrhoea, low BMD, recent BSI)Intensive medical intervention, partial restrictions
🔴 REDMajor indicators (BMD < -2, multiple fractures, endocrine dysfunction)Temporary withdrawal from sport, full medical management

Triad Cumulative Risk Assessment and clinical stratification

For the clinician on the ground, the most widely used tool remains the Triad Cumulative Risk Assessment Score (Tenforde 2017), which aggregates 6 indicators into a score from 0 to 12 points.⁵
Indicator0 points1 point2 points
Energy availabilityNo restrictionRestriction without an eating disorderCurrent or past eating disorder
BMI (kg/m²)≥ 18,517,5-18,5< 17,5
Age at menarche< 15 years15-16 years≥ 16 years
Menstrual cycles per year≥ 96-9< 6 or amenorrhoea
BMD Z-score≥ -1,0-1,0 à -2,0≤ -2,0
History of BSI / fractureNone1 previous episode≥ 2 or trabecular
The total score categorises the risk: 0-1 = low, 2-5 = moderate (×2 BSI risk), ≥6 = high (×4 BSI risk) in Tenforde's 2017 prospective cohort of 89 collegiate female runners.⁵

🚩 REDs warning signs to screen for systematically

  • Women: amenorrhoea > 3 months, irregular cycles, delayed menarche, loss of cycles after stopping the pill
  • Men: reduced libido, erectile dysfunction, chronic fatigue, performance plateauing or declining
  • Everyone: multiple or recurrent BSIs, delayed healing, repeated upper respiratory infections, falling BMI, dietary restriction
  • Adolescents: growth delay, delayed puberty, fractures from low-energy trauma
A note on men: long overlooked, REDs affects men too. The prevalence of LEA in male athletes is estimated at 49 % in a recent meta-analysis (Gallant 2025), and is particularly marked in endurance and weight-category sports.¹¹ The Triad score has been modified for men and validated as predictive of BSI in male runners in 2019 (Kraus, Tenforde, Nattiv).¹²

Key points

  • BSI risk is 2 to 4× higher in women, linked to the hormonal, nutritional and bone triad.
  • Amenorrhoea multiplies the risk by 4.7 (95 % CI 1.5-15).
  • The REDs affects men too (LEA prevalence around 49 %); the exclusively “female triad” concept should be abandoned.
  • The IOC's 2023 CAT2 (traffic lights ⊕ amber) structures the decision to return to training.
  • Any multiple or bilateral BSI → a systematic REDs work-up (cycles, DEXA, vitamin D, ferritin, endocrine panel).
Bibliography
  1. Sale C, Elliott-Sale KJ. Nutrition and Athlete Bone Health. Sports Med. 2019;49(Suppl 2):139-151. PMID 31696454.
  2. Goolsby MA, Boniquit N. Bone Health in Athletes. Sports Health. 2017;9(2):108-117. PMID 27821574.
  3. Tenforde AS, Ackerman KE, Bouxsein ML, et al. Factors Associated With High-Risk and Low-Risk Bone Stress Injury in Female Runners. Orthop J Sports Med. 2024;12(5):23259671241246227. PMID 38779133.
  4. Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 IOC consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073-1097. PMID 37752011.
  5. Tenforde AS, Carlson JL, Chang A, et al. Association of the Female Athlete Triad Risk Assessment Stratification to the Development of Bone Stress Injuries in Collegiate Athletes. Am J Sports Med. 2017;45(2):302-310. PMID 28038316.
  6. Barrack MT, Gibbs JC, De Souza MJ, et al. Higher incidence of bone stress injuries with increasing Female Athlete Triad-related risk factors. Am J Sports Med. 2014;42(4):949-958. DOI 10.1177/0363546513520295.
  7. Ackerman KE, Holtzman B, Cooper KM, et al. Low energy availability surrogates correlate with health and performance consequences of REDs. Br J Sports Med. 2019;53(10):628-633. PMID 29860237.
  8. Loucks AB, Kiens B, Wright HH. Energy availability in athletes. J Sports Sci. 2011;29 Suppl 1:S7-15. PMID 21793767.
  9. Stellingwerff T, Mountjoy M, McCluskey WT, et al. Review of the scientific rationale, development and validation of the IOC REDs Clinical Assessment Tool V.2 (CAT2). Br J Sports Med. 2023;57(17):1109-1118. PMID 37752002.
  10. Hoenig T, Ackerman KE, Beck BR, et al. Bone stress injuries. Nat Rev Dis Primers. 2022;8(1):26. PMID 35484131.
  11. Gallant TL, Ong LF, Wong L, et al. Low Energy Availability and Relative Energy Deficiency in Sport: A Systematic Review and Meta-analysis. Sports Med. 2025;55(2):325-339. PMID 39485653.
  12. Kraus E, Tenforde AS, Nattiv A, et al. Bone stress injuries in male distance runners: higher modified Female Athlete Triad Cumulative Risk Assessment scores predict increased rates of injury. Br J Sports Med. 2019;53(4):237-242. PMID 30580252.

How do you diagnose a stress fracture with certainty?

In this chapter: targeted history-taking centred on training load and REDs, clinical examination (focal palpation, hop test, fulcrum test), the comparative diagnostic performance of the imaging tests (MRI the gold standard), the high/low risk anatomical classification and the Fredericson MRI classification, and a complete decision algorithm.
The diagnosis rests on a tripod: targeted history, localising clinical examination, imaging matched to the level of risk. A strong clinical suspicion almost always precedes confirmation on imaging. 🩺

Targeted history-taking and red flags

Systematic questioning looks for a cluster of highly suggestive findings:
  • Insidious, localised pain, at first on exercise then coming on ever earlier, and at rest if it progresses.¹
  • A recent change (2-6 weeks) in training load: volume, intensity, frequency, terrain, footwear.²
  • Systemic intrinsic factors: amenorrhoea or oligomenorrhoea, a history of eating disorder, low BMI, a personal or family history of BSI or fragility fracture.³
  • Vitamin D and calcium status: to be checked systematically, because it is correctable.⁴

🚩 Red flags: immediate medical referral

  • Groin or buttock pain in a runner, especially on single-leg loading → suspected femoral neck fracture
  • Anterior tibial pain (the hard side) that persists → a high-risk site (the “dreaded black line”)
  • Pain on the dorsum of the foot centred on the N spot of the navicular → poor blood supply, risk of non-union
  • Multiple or bilateral fractures → systematic search for REDs and an endocrine work-up
  • Night pain, weight loss, fever → rule out tumour or infection
  • Recent corticosteroid therapy or an endocrine disorder → systematic bone densitometry

Clinical examination and differential diagnosis

The clinical examination aims to locate the painful area precisely and to reproduce the symptoms.
  • Focal bone palpation: exquisite tenderness over a precise bony point, the most reliable sign for accessible sites (tibia, metatarsals, fibula).⁵
  • Single-leg hop test: positive if the athlete cannot perform several hops without pain. Useful for lower-limb BSI.¹
  • Fulcrum test for the femur, percussion at a distance and the tuning fork for the tibia: variable sensitivity, low specificity.⁵
The differential diagnosis must systematically rule out:
  • The medial tibial stress syndrome (diffuse pain over > 5 cm along the posteromedial border).
  • The tendinopathies (pain on loading the tendon, not on bone impact).
  • The chronic exertional compartment syndrome (cramping that eases at rest).
  • The radiculopathies or nerve compression (particularly for sacral BSIs, which mimic sciatica).⁶

Imaging: why and how to classify?

The diagnostic performances are now well established:

🔬 Comparative diagnostic performance of the imaging tests

MRI is the gold standard for early marrow oedema

Comparative sensitivity of imaging tests in BSI Investigation Sensitivity (%) 0 33 66 100 Radiograph (early) 10-15 % Radiograph (follow-up) 30-70 % Three-phase bone scan ~90 % MRI (reference) ~100 % CT (cortex) ~75 %

Sources: Hoenig 2022 AJSM (meta-analysis), Tenforde 2016, Pegrum 2012.⁷٬⁸

Two complementary classifications guide the decision: 1. Anatomical classification (high risk vs low risk) , which determines how aggressive management must be:⁹٬¹⁰
CategorySitesCourse of action
High riskFemoral neck (tension side), navicular, anterior tibia, medial malleolus, base of the 5th MT, sesamoids, patellaComplete offloading, surgical opinion, imaging follow-up; risk of non-union and necrosis
Low riskPosteromedial tibia, fibula, MT 2-3-4, pubis, sacrum (usually)Pain-guided load modification, cross-training, gradual resumption
2. The Fredericson MRI classification (grades 1 to 4), correlated with the time to return to sport:⁷٬¹¹

📈 Time to return to sport by Fredericson MRI grade

Hoenig 2022 meta-analysis, pooling 16 studies and 560 BSIs

Time to RTS by Fredericson MRI grade MRI grade Median time to RTS (days) Grade 142 j Grade 270 j Grade 384 j Grade 498 j > 90 % of athletes return to sport. r = 0.554, p = 0.001.

Hoenig T, Tenforde AS, Strahl A, et al. Am J Sports Med. 2022;50(3):834-844.⁷

Diagnostic decision algorithm

To bring clinical suspicion, imaging and risk stratification together into one coherent decision, here is the recommended summary algorithm.

🧭 Decision algorithm: from suspicion to treatment plan

A synthesis of Hoenig Delphi 2025 + IOC REDs 2023 + Warden JOSPT 2021

BSI decision algorithm from suspicion to treatment Focal bone pain on exercise + a recent change in training load Targeted history + clinical examination Focal palpation • Hop test • Fulcrum test • Red flags • REDs screening Clinical suspicion? Cluster of findings LOW STRONG Clinical follow-up at 2 wks Relative rest Reassessment MRI as a priority Reference (Se ~100 %) Marrow oedema Site of the lesion? Anatomical stratification LOW RISK posteromedial tibia, fibula, MT 2-3-4, pubis HIGH RISK femoral neck, navicular, anterior tibia, 5th MT, sesamoids Outpatient management • Load modification (pain-free) • Cross-training • Gradual resumption in 4 phases Specialist opinion • Complete offloading • Surgical opinion • Follow-up imaging Correcting the causal factors, always Training error • REDs/Triad CRA • Vit D / calcium • Biomechanics • Equipment Therapeutic education and criteria-based return-to-sport planning Criteria-based return to sport > 90 % success; watch for recurrence (~20-30 %)

An algorithm bringing together the Hoenig Delphi 2025 + IOC REDs 2023 + Warden JOSPT 2021 recommendations.¹²٬¹³٬¹⁴

Key points

  • Adopt the term BSI and think in terms of a continuum.
  • MRI is the reference investigation . The initial radiograph is falsely reassuring in 70-90 % of early cases.
  • Stratify systematically into high risk vs low risk before any treatment decision.
  • The Fredericson MRI grade is predictive of the time to RTS (42 to 98 days).
  • Every decision must include correcting the systemic causes (REDs, load, biomechanics).
Bibliography
  1. Warden SJ, Davis IS, Fredericson M. Management and prevention of bone stress injuries in long-distance runners. J Orthop Sports Phys Ther. 2014;44(10):749-65. PMID 25103133.
  2. Warden SJ, Edwards WB, Willy RW. Preventing bone stress injuries in runners with optimal workload. Curr Osteoporos Rep. 2021;19(3):298-307. PMID 33635519.
  3. Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 IOC consensus statement on REDs. Br J Sports Med. 2023;57(17):1073-1097. PMID 37752011.
  4. Sale C, Elliott-Sale KJ. Nutrition and Athlete Bone Health. Sports Med. 2019;49(Suppl 2):139-151. PMID 31696454.
  5. Pegrum J, Crisp T, Padhiar N. Diagnosis and management of bone stress injuries of the lower limb in athletes. BMJ. 2012;344:e2511. PMID 22532009.
  6. Ferreira GS, Almeida RN, Pinto JFP. Sacral stress fracture in a young-adult, long-distance runner: an underestimated cause of low back pain. BMJ Case Rep. 2023;16(9):e255959. PMC10481734.
  7. Hoenig T, Tenforde AS, Strahl A, et al. Does MRI Grading Correlate With Return to Sports After Bone Stress Injuries? A Systematic Review and Meta-analysis. Am J Sports Med. 2022;50(3):834-844. PMID 33720786.
  8. Tenforde AS, Kraus E, Fredericson M. Bone Stress Injuries in Runners. Phys Med Rehabil Clin N Am. 2016;27(1):139-149. PMID 26616181.
  9. McInnis KC, Ramey LN. High-Risk Stress Fractures: Diagnosis and Management. PM R. 2016;8(3 Suppl):S113-S124. PMID 26972260.
  10. Hoenig T, Eissele J, Strahl A, et al. Return to sport following low-risk and high-risk bone stress injuries: a systematic review and meta-analysis. Br J Sports Med. 2023;57(7):427-432. DOI 10.1136/bjsports-2022-106328.
  11. Fredericson M, Jennings F, Beaulieu C, Matheson GO. Stress fractures in athletes. Top Magn Reson Imaging. 2006;17(5):309-325. PMID 17414993.
  12. Hoenig T, Hollander K, Ackerman KE, et al. International Delphi consensus on bone stress injuries in athletes. Br J Sports Med. 2025;59(2):85-94. PMID 39638438.
  13. Warden SJ, Edwards WB, Willy RW. Optimal Load for Managing Low-Risk Tibial and Metatarsal Bone Stress Injuries in Runners. J Orthop Sports Phys Ther. 2021;51(7):322-330. PMID 33962529.
  14. Nattiv A, Kennedy G, Barrack MT, et al. Correlation of MRI Grading of Bone Stress Injuries With Clinical Risk Factors and Return to Play. Am J Sports Med. 2013;41(8):1930-1941. PMID 23825184.

What is the most effective treatment strategy?

In this chapter: the hierarchy of interventions (load first, modalities second), a four-phase graded resumption after Warden 2021, the acute-to-chronic workload ratio (ACWR) with its 0.8-1.3 sweet spot, a comparison table of modalities against GRADE level of evidence, and the GRADE pyramid as horizontal cards.
The guiding principle, formalised by the 2025 international Delphi consensus, is a dynamic balance between mechanical load and the capacity to repair. Treatment is largely load-driven and symptom-driven, not time-driven.¹٬²

Hierarchy of recommended interventions

  1. Stopping the activity that provokes the pain: immediate and non-negotiable. The key idea is relative rest, not absolute rest.³
  2. Offloading: complete and protected with crutches for high-risk BSIs; partial, or simply activity modification, for low-risk BSIs.⁴
  3. Identifying and correcting the causal factors: training errors, biomechanics, equipment, and above all a systemic assessment (REDs, vitamin D, calcium, energy balance).⁵
  4. Nutritional optimisation: aim for 1000-1300 mg/day of calcium and a serum 25(OH)D > 75 nmol/L (> 30 ng/mL), ideally > 100 nmol/L.⁶

Progressive load and the acute-to-chronic ratio

Rehabilitation is built around optimal loading, defined by Warden et al. as “the load that produces no symptoms during, after, or the day following the activity”.² 🏃

🔄 Resumption algorithm for low-risk BSI (Warden 2021)

Cross-training → walk-run → continuous running → sport-specific

Four-phase graded resumption after low-risk BSI Phase 1: relative rest + cross-training (cycling, aqua-jogging, swimming) Exit criterion: no daily pain for 5 consecutive days Phase 2: walking, then walk-run (1 min running / 4 min walking, ×6) Pain monitored; running time progressed every 48 h Phase 3: continuous running, increasing volume before intensity The “10 % rule” as a guide (not absolute); ACWR < 1.2 Phase 4: sport-specific training, technical patterns, jumping Symmetrical functional tests; return to competition after 2-4 symptom-free weeks ⚠ Pain returning = go back to the previous phase

Adapted from Warden, Edwards, Willy. JOSPT 2021.²

The 10 % rule (do not increase weekly volume by more than 10 %) remains a useful teaching guide, although the formal evidence base is weak.⁷ The acute-to-chronic workload ratio (ACWR) offers a finer metric: the ratio of the current week's load (acute, 7 days) to the average of the 4 preceding weeks (chronic, 28 days). A “sweet spot” between 0.8 and 1.3 is thought to carry the lowest risk, whereas a risk zone ≥ 1.5 significantly multiplies injury risk.⁷٬⁸ 📊

📈 Acute-to-chronic ratio (ACWR) and injury risk

Risk zones by ratio (Gabbett 2016, Maupin 2020)

Risk zones by acute-to-chronic workload ratio Relative probability of injury 0,5 0,8 1,0 1,3 1,5 1,8 2,0+ Acute (7 d) / chronic (28 d) ratio SWEET SPOT 0,8 - 1,3 UNDERLOADING deconditioning RISK ZONE ≥ 1.5: risk ×2-4 CAUTION to be monitored Min. risk Max. risk

Adapted from Gabbett 2016 (BJSM) and Maupin 2020 (Open Access J Sports Med).⁷٬⁸ ⚠ A critical note: the “sweet spot” has attracted methodological criticism (coupling bias). Use it as a guide, not as an absolute rule.

In clinical practice: a high, well-prepared chronic load is protective ; an abrupt increase (> 50 % in one week compared with the previous 4) is harmful. For the runner after a BSI, aim for an ACWR < 1.2 during the first 6-8 weeks of resumption.²

Adjunctive modalities and GRADE level of evidence

ModalityIndicationLevel of evidenceComment
Load managementAll BSIsGRADE highThe cornerstone; the benefit is not in doubt
Cross-training without impactMaintaining fitnessGRADE highAvoids deconditioning, a universal recommendation
Muscle strengtheningCorrecting deficitsGRADE moderateIndirect benefit (biomechanics, bone quality)
Ca / vitamin D supplementsIf deficiency is provenGRADE moderateCalcium 2000 mg + vitamin D 800 IU lowered incidence in recruits
ESWT (shockwave)Delayed union, non-unionGRADE low62-72 % union in non-unions; no solid RCT in acute BSI
LIPUS (pulsed ultrasound)Accelerating healingGRADE very lowLimited and heterogeneous data in BSI
Manual therapyAssociated tightness or stiffnessGRADE very lowDoes not accelerate bone healing; an adjunctive role
BisphosphonatesRefractory BSI ± severe REDsGRADE very lowAn exceptional indication, specialist opinion required
The appeal of technology sometimes eclipses the fundamentals. No modality replaces correcting the causes: load, REDs, biomechanics.

Key points

  • Both Load modification and cross-training are the only elements graded GRADE high.
  • Rehabilitation is symptom-guided, not calendar-guided.
  • The acute-to-chronic ratio (ACWR) should stay in the 0.8-1.3 sweet spot.
  • ESWT is of moderate value only in delayed union.
  • No modality replaces correcting the causes (load, REDs, biomechanics).
Bibliography
  1. Hoenig T, Hollander K, Ackerman KE, et al. International Delphi consensus on bone stress injuries in athletes. Br J Sports Med. 2025;59(2):85-94. PMID 39638438.
  2. Warden SJ, Edwards WB, Willy RW. Optimal Load for Managing Low-Risk Tibial and Metatarsal Bone Stress Injuries in Runners. J Orthop Sports Phys Ther. 2021;51(7):322-330. PMID 33962529.
  3. Warden SJ, Davis IS, Fredericson M. Management and prevention of bone stress injuries in long-distance runners. J Orthop Sports Phys Ther. 2014;44(10):749-65. PMID 25103133.
  4. McInnis KC, Ramey LN. High-Risk Stress Fractures: Diagnosis and Management. PM R. 2016;8(3 Suppl):S113-S124. PMID 26972260.
  5. Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 IOC consensus statement on REDs. Br J Sports Med. 2023;57(17):1073-1097. PMID 37752011.
  6. Sale C, Elliott-Sale KJ. Nutrition and Athlete Bone Health. Sports Med. 2019;49(Suppl 2):139-151. PMID 31696454.
  7. Gabbett TJ. The training-injury prevention paradox: should athletes be training smarter and harder? Br J Sports Med. 2016;50(5):273-280. PMID 26758673.
  8. Maupin D, Schram B, Canetti E, Orr R. The Relationship Between Acute: Chronic Workload Ratios and Injury Risk in Sports: A Systematic Review. Open Access J Sports Med. 2020;11:51-75. PMID 32158285.
  9. Soligard T, Schwellnus M, Alonso JM, et al. How much is too much? (Part 1) IOC consensus statement on load in sport and risk of injury. Br J Sports Med. 2016;50(17):1030-1041. PMID 27535989.
  10. McDaniel M, Eltman NR, Pan J, Swanson RL. Evaluation of Low-Intensity Pulsed Ultrasound on Stress Fractures. Cureus. 2023;15(10):e47896. PMID 38024090.
  11. Putukian M. The psychological response to injury in student athletes. Br J Sports Med. 2016;50(3):145-148. PMID 26719498.

How do you prevent recurrence and plan the return to sport?

In this chapter: self-management as the best protective factor (a training diary, REDs screening with CAT2), the clinical, functional, psychological and contextual criteria for clearing a return to sport, and the place of follow-up imaging.
Recurrence is a real concern: 20 à 30 % of runners will have a further BSI, with a risk about 3 times higher in women.¹٬² A structured and individualised approach is essential.

Self-management and therapeutic education

Therapeutic education is the best protective factor. Three priority lines:
  • Understanding the concept of cumulative overload: the athlete must know that the trigger is not an acute event but an accumulation of small loads. Volume progression remains the number one modifiable factor.³٬⁴
  • Detecting REDs: screening with the REDs Clinical Assessment Tool v2 (CAT2) from the IOC 2023, with questions on menstrual cycles, BMI, eating behaviour, performance and chronic fatigue.⁵ 🧠
  • Keeping a training diary: loads, pain, sleep, rating of perceived exertion (RPE), mood, to pick up the warning signals early. 📝

Performance-based return-to-sport criteria

Return to sport is not an event but a criteria-based process. The decision brings together:
  • Clinical criteria: no pain on palpation, on the hop test, or on 30 minutes of continuous running, and no symptoms the following day.⁶
  • Functional criteria: strength balance, neuromuscular control, quality of the running pattern (video analysis recommended for runners with recurrent injury).⁶
  • Psychological criteria: assessing kinesiophobia (TSK-11 scale) and confidence in the ability to resume, both often overlooked.⁷
  • Contextual criteria: correction of the causal factors (REDs, load, equipment); without this, recurrence is predictable.⁵
The role of imaging in clearing a return remains debated. Radiological healing (resolution of marrow oedema on MRI) often lags several weeks or months behind the disappearance of symptoms; a normal MRI is not required to clear a return in most low-risk cases.⁸٬⁹ For high-risk BSIs (femoral neck, navicular, anterior tibia), on the other hand, an imaging check remains prudent before returning to high-impact loading.¹⁰
Return to sport is never a date. It is the sum of verifiable criteria: no pain, function restored, fear of movement mastered, causes corrected.

Key points

  • Preventing recurrence rests on education and on correcting the causes.
  • RTS is criteria-based, not date-based.
  • Both REDs and kinesiophobia are the most underestimated factors.
  • Follow-up imaging is useful for high-risk sites and dispensable for asymptomatic low-risk BSIs.
Bibliography
  1. Wright AA, Taylor JB, Ford KR, Siska L, Smoliga JM. Risk factors associated with lower extremity stress fractures in runners. Br J Sports Med. 2015;49(23):1517-23. PMID 26582192.
  2. Tenforde AS, Ackerman KE, Bouxsein ML, et al. Factors Associated With High-Risk and Low-Risk Bone Stress Injury in Female Runners. Orthop J Sports Med. 2024;12(5):23259671241246227. PMID 38779133.
  3. Warden SJ, Edwards WB, Willy RW. Preventing bone stress injuries in runners with optimal workload. Curr Osteoporos Rep. 2021;19(3):298-307. PMID 33635519.
  4. Soligard T, Schwellnus M, Alonso JM, et al. IOC consensus statement on load in sport and risk of injury. Br J Sports Med. 2016;50(17):1030-1041. PMID 27535989.
  5. Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 IOC consensus statement on REDs. Br J Sports Med. 2023;57(17):1073-1097. PMID 37752011.
  6. Warden SJ, Edwards WB, Willy RW. Optimal Load for Managing Low-Risk Tibial and Metatarsal BSI in Runners. J Orthop Sports Phys Ther. 2021;51(7):322-330. PMID 33962529.
  7. Putukian M. The psychological response to injury in student athletes. Br J Sports Med. 2016;50(3):145-148. PMID 26719498.
  8. Hoenig T, Tenforde AS, Strahl A, et al. Does MRI Grading Correlate With Return to Sports After BSI? Am J Sports Med. 2022;50(3):834-844. PMID 33720786.
  9. Hoenig T, Eissele J, Strahl A, et al. Return to sport following low-risk and high-risk BSI: a SR/MA. Br J Sports Med. 2023;57(7):427-432. DOI 10.1136/bjsports-2022-106328.
  10. McInnis KC, Ramey LN. High-Risk Stress Fractures: Diagnosis and Management. PM R. 2016;8(3 Suppl):S113-S124. PMID 26972260.

What do the published clinical cases teach us?

Three clinical cases published in peer-reviewed journals (BMJ Case Rep 2023, KSSTA 2019, J Foot Ankle Surg 2017) illustrate the range of presentations and the diagnostic traps of BSI.

Case 1: female runner, buttock pain simulating sciatica

A distance runner presenting with right buttock and low back pain radiating down the back of the thigh, which began after a marathon. Neurological tests negative (straight leg raise, slump test). Given the persistence,MRI reveals extensive marrow oedema of the right sacral ala, consistent with a sacral BSI. Management: gradual offloading, nutritional treatment, resumption at 8 weeks. Key lesson: any “sciatica” in a runner that does not respond to standard treatment calls for a targeted MRI of the sacrum. Source: Ferreira et al. BMJ Case Reports 2023: PMC10481734.¹

Case 2: elite female runner, bilateral femoral neck stress fractures

A high-performance runner presenting with chronic bilateral groin pain, dismissed as “psoas tendinopathy”.MRI reveals bilateral femoral neck BSIs on the compression side. Investigation uncovers secondary amenorrhoea (> 1 year), a low BMI and insufficient energy intake, a picture of REDs. Multidisciplinary management: orthopaedic (prophylactic screw fixation), nutritional, psychological and endocrine. Key lesson: any bilateral or multiple BSI calls for systematic REDs screening and a full endocrine work-up. Source: Souza & Fariña. Knee Surg Sports Traumatol Arthrosc 2019: PMID 31451476.²

Case 3: a series of 62 navicular fractures in a sporting cohort

A prospective series of 59 patients (62 fractures) over 11 years (impact sports and running). The key finding: a mean diagnostic delay of 4 months before correct management (pain centred on the dorsal N spot ), with bone scan or MRI frequently needed (radiographs normal in most cases). Mean time to return to activity 4-6 months. The risk of recurrence was significantly associated with poor adherence to the initial offloading. Key lesson: navicular BSI is under-diagnosed and carries a high risk of non-union. Dorsal foot pain at the N spot calls for MRI even when the radiograph is normal. Source: Saxena et al. J Foot Ankle Surg 2017: PMID 28842101.³
BSI is a great imitator. Sciatica, tendinopathy, sacroiliitis, piriformis syndrome: all these diagnoses must remain provisional if pain persists in an endurance athlete.
Cross-cutting lessons:
  • BSI is a great imitator : demand a systematic diagnostic rethink if pain persists.
  • Any multifocal or bilateral BSI calls for systematic REDs screening.
  • Sites with a precarious blood supply (navicular, femoral neck, anterior tibia) demand great caution and early specialist referral.

Key points

  • The diagnosis is above all clinical : focal bone pain in an athlete after a change in load.
  • Early MRI is the investigation of choice where doubt persists.
  • Think of the imitators and the red flags : sciatica → sacrum, psoas tendinopathy → femoral neck.
  • Bilateral or multiple fractures call for a search for a systemic cause (REDs).
Bibliography
  1. Ferreira GS, Almeida RN, Pinto JFP. Sacral stress fracture in a young-adult, long-distance runner: an underestimated cause of low back pain. BMJ Case Rep. 2023;16(9):e255959. PMC10481734.
  2. Souza JM, Fariña D. Bilateral femoral neck stress fractures in a high-performance young female runner: a case report. Knee Surg Sports Traumatol Arthrosc. 2019. PMID 31451476.
  3. Saxena A, Behan SA, Valerio DL, Frosch DL. Navicular Stress Fracture Outcomes in Athletes: Analysis of 62 Injuries. J Foot Ankle Surg. 2017;56(5):943-948. PMID 28842101.
  4. Griffin LY, Mahmoud A, Bouchard J, Akar B, Murray JC. Femoral neck stress fractures in military personnel: a case series. Knee Surg Sports Traumatol Arthrosc. 2009;17(11):1389-1393. PMID 19090388.
  5. Hayes M, Smith TR, Bracken P, et al. Development of a new guideline to facilitate diagnosis and management of rib stress injuries in rowers. BMJ Open Sport Exerc Med. 2015;1(1):e000018. PMC4535300.

How do you apply these recommendations in practice?

In this chapter: referral criteria (sports physician, surgeon, dietitian, psychologist), outcome measurement through PROMs and functional tests, the red flags specific to BSI, and the barriers to and facilitators of evidence-based implementation.
Effective implementation of the recommendations rests on three pillars: interprofessional collaboration, shared decision-making with the patient, and systematic outcome measurement. 🧑‍⚕️

When and to which professionals should you refer?

Every high-risk BSI must be referred without delay to a sports physician or an orthopaedic surgeon. A nutrition or endocrinology opinion is essential in multiple BSIs, a history of REDs or low BMD. And psychological support may be warranted where kinesiophobia is marked or contributing psychosocial factors are present (perfectionism, poor social support).¹٬²

🚩 Red flags calling for referral

  • A high-risk site (femoral neck, navicular, anterior tibia, base of the 5th MT) → urgent surgical opinion
  • Multiple / bilateral / recurrent BSIs → systematic REDs work-up (endocrinology, nutrition)
  • Night pain, weight loss, fever → rule out tumour or infection
  • Failure of conservative treatment after 6 weeks → repeat imaging plus specialist opinion
  • High kinesiophobia (TSK-11 > 37) → psychological referral

Measuring outcomes and overcoming barriers to implementation

Building in Patient-Reported Outcome Measures (PROMs), the VISA-A score modified for BSI, a numerical pain scale, a return-to-sport scale, should go hand in hand with performance tests (hop test, 30 minutes of continuous running). Beyond statistical significance, aim for the Minimal Clinically Important Difference (MCID).³ Red flags in practice: apply Verhagen's 2016 grid systematically to exclude serious conditions in any persistent bone pain.⁴ Shared decision-making: adherence to the treatment plan is better when the athlete takes part in the choices (modality, timetable for resumption, level of risk accepted). The Cochrane review by Légaré 2018 confirms the clinical value of this approach.² Barriers to implementation: the most frequently reported obstacles are lack of time, lack of skills in critical appraisal of the literature, and insufficient organisational support. The facilitators include strong leadership, access to resources and continuing education.
Clinical expertise is not the mechanical application of guidelines: it is integrating them with clinical experience and the patient's values. That is the art of clinical science.

Key points

  • Every high-risk BSI calls for immediate referral to a sports physician or surgeon.
  • Multiple BSIs → systematic REDs work-up (cycles, DEXA, vitamin D, ferritin, endocrinology).
  • Measure outcomes with standardised PROMs and functional tests, aiming for the MCID.
  • A Shared decision-making improves adherence and outcomes.
  • Overcoming organisational barriers requires a multifaceted approach (training, leadership, audit and feedback).
Bibliography
  1. Putukian M. The psychological response to injury in student athletes: a narrative review. Br J Sports Med. 2016;50(3):145-148. PMID 26719498.
  2. Légaré F, Adekpedjou R, Stacey D, et al. Interventions for increasing the use of shared decision making by healthcare professionals. Cochrane Database Syst Rev. 2018;7(7):CD006732. PMID 30025154.
  3. Robertson GAJ, Wood AM. Lower limb stress fractures in sport: optimising their management and outcome. World J Orthop. 2017;8(3):242-255. PMID 28361017.
  4. Verhagen AP, Downie A, Popal N, Maher C, Koes BW. Red flags presented in current low back pain guidelines: a review. Eur Spine J. 2016;25(9):2788-2802. PMID 27376890.
  5. Hoenig T, Hollander K, Ackerman KE, et al. International Delphi consensus on bone stress injuries in athletes. Br J Sports Med. 2025;59(2):85-94. PMID 39638438.

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This article has undergone rigorous bibliographic checking: every reference cited is linked to a verified PubMed PMID or CrossRef DOI. The figures and claims are sourced. The clinical cases cited come from the published literature.

Last revisedMay 2026 MethodA synthesis of Delphi 2025 + IOC REDs 2023 + Nat Rev 2022 + BJSM/AJSM/JOSPT meta-analyses Level of evidenceGRADE stated explicitly by section (high to very low) Conflicts of interestNone declared A question, or spotted an error?WhatsApp button at the bottom right of the screen 💬

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Marked for life by his first four-hour lecture without a single image, he took a master’s in instructional design so that it would never happen to anyone again. He hunts down publication bias and unreadable slides with the same intransigence.

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