Fatigue vs Insufficiency | High-Risk Sites | RED-S | Imaging Continuum | Load Management
- Fatigue fractures = abnormal stress on normal bone; insufficiency fractures = normal stress on abnormal bone
- Five high-risk sites: femoral neck (tension side), anterior tibial cortex, tarsal navicular, 5th metatarsal base, hallux sesamoid
- MRI is gold standard — X-ray sensitivity is only 15-30% in the first 2-3 weeks
- RED-S (Relative Energy Deficiency in Sport) is the modern term replacing 'female athlete triad' and includes male athletes
- Tension-side femoral neck fractures need urgent fixation — risk of displaced fracture and AVN
- “If X-ray is normal but clinical suspicion is high, get an MRI — do not wait for X-ray changes
- “Tension-side femoral neck stress fracture = ORIF, do not trial non-operative management
- “Anterior tibial 'dreaded black line' = high risk, consider intramedullary nailing
- “RED-S screening is mandatory in any athlete with recurrent stress fractures
Overview and Epidemiology
Stress fractures account for up to 20% of all injuries in sports medicine clinics and are the most common overuse injury in military recruits and distance runners. High-risk stress fractures (tension-side femoral neck, navicular, anterior tibia, 5th metatarsal base, sesamoid) can progress to complete fracture or nonunion if missed. Early radiographs are often normal, so the diagnosis is clinical first and depends on a high index of suspicion. Every stress fracture in an athlete warrants screening for RED-S.
Who. The incidence is 5-30% in runners and military recruits. Female athletes carry 2-4 times the risk of males, through RED-S and menstrual dysfunction. The tibia is the most common site, at its posterior-medial cortex, which is a low-risk site.
Training load. Training errors are rapid increases in volume, intensity or frequency. An increase of more than 10% a week is a risk factor, both for a stress fracture and for its recurrence.
Energy availability. Low energy availability, from disordered eating or RED-S, is the risk factor worth putting a number on. Energy availability is dietary intake minus exercise energy expenditure, expressed per kg of fat-free mass, and the ACSM position stand puts the threshold plainly: most of the reproductive and skeletal effects appear below 30 kcal/kg fat-free mass per day. That converts a vague "eating too little" into a figure you can calculate at the bedside.
Low energy availability, not low body weight and not amenorrhoea, is the driver of the other two components of the triad, menstrual dysfunction and low BMD. The remaining risk factors fall into bone density, biomechanics and medication:
- Low BMD, osteoporosis, a previous stress fracture
- Leg length discrepancy, foot type, running surface
- Bisphosphonates (atypical fractures, below), corticosteroids, aromatase inhibitors
Pathophysiology
Damage against repair. A stress fracture is an imbalance between microdamage accumulation and bone remodelling repair. Normal bone remodels constantly: osteoclastic resorption cuts cavities that osteoblasts fill with new bone, resorption taking 2-3 weeks and formation 3-4 months. With overuse, increased resorption outpaces formation.
A continuum. The injury runs from bone stress reaction (oedema, no fracture line) to frank cortical fracture. If loading continues:
- Weeks 1-2: oedema and microcracks, the bone stress reaction
- Weeks 3-4: the microcracks coalesce
- Weeks 4-8: a cortical fracture line becomes visible
Removing the load early allows the remodelling cycle to catch up.
Fatigue or insufficiency. When repetitive loading outpaces repair in normal bone, microdamage coalesces into a fatigue fracture. When the bone itself is weakened (osteoporosis, RED-S), even normal physiological loads cause an insufficiency fracture.
- Fatigue Fracture
- Abnormal repetitive load on normal bone
- Insufficiency Fracture
- Normal physiological load on weakened bone
- Fatigue Fracture
- Runner, military recruit, dancer, athlete
- Insufficiency Fracture
- Elderly, osteoporotic, bisphosphonate user, rheumatoid arthritis
- Fatigue Fracture
- Normal bone mineral density
- Insufficiency Fracture
- Low BMD, osteomalacia, metabolic bone disease
- Fatigue Fracture
- Load management, relative rest, return to sport
- Insufficiency Fracture
- Treat underlying bone health (vitamin D, bisphosphonate review, DEXA)
- Fatigue Fracture
- Tibia, metatarsals, femoral neck, navicular, fibula
- Insufficiency Fracture
- Vertebral body, sacrum, pubic ramus, femoral neck, calcaneus
Tension and compression. Bone on the compression side can remodel and heal under compression, so these sites are usually low-risk (the inferomedial femoral neck, the posterior-medial tibia). On the tension side bone fails under tensile stress and the fracture propagates rather than heals; these sites are high-risk (the superolateral femoral neck, the anterior tibial cortex). Tension-side fractures need urgent fixation or strict non-weight-bearing, and compression-side fractures can often be managed conservatively.
Classification and Types
High risk or low risk. The most important classification, because it decides management. High-risk sites lie on the tension side of a bone or in an area of poor vascularity; they have a high rate of nonunion, delayed union or progression to complete fracture, and need aggressive, often surgical, management. Low-risk sites lie on the compression side and usually heal with activity modification.
- Site
- Femoral neck
- Side/Location
- Tension (superolateral) side
- First-Line Treatment
- Urgent cannulated screw fixation
- Site
- Anterior tibial cortex
- Side/Location
- Tension (anterior) mid-shaft
- First-Line Treatment
- IM nail or excision + bone graft if refractory
- Site
- Tarsal navicular
- Side/Location
- Central third (watershed)
- First-Line Treatment
- NWB cast 6-8 weeks; ORIF if displaced
- Site
- 5th metatarsal base
- Side/Location
- Jones fracture (metaphyseal-diaphyseal junction)
- First-Line Treatment
- Percutaneous screw (athletes) vs NWB cast
- Site
- Hallux sesamoid
- Side/Location
- Medial (tibial) sesamoid
- First-Line Treatment
- NWB + sesamoid pad; excision if refractory
- Site
- Posterior-medial tibia
- Side/Location
- Compression (posteromedial) cortex
- First-Line Treatment
- Relative rest, graded return 6-8 weeks
- Site
- Femoral neck (compression)
- Side/Location
- Inferomedial side
- First-Line Treatment
- NWB until pain-free, then progressive WB
- Site
- 2nd-4th metatarsal shaft
- Side/Location
- Mid-shaft (march fracture)
- First-Line Treatment
- Stiff shoe / walking boot 4-6 weeks
- Site
- Fibula
- Side/Location
- Distal third (compression)
- First-Line Treatment
- Relative rest; occasionally boot for comfort
- Site
- Calcaneus
- Side/Location
- Posterior (compression)
- First-Line Treatment
- Relative rest, progressive weight-bearing
NAFFSHigh-Risk Stress Fracture Sites
Hook:NAFFS — Not A Friendly Fracture Site! These five locations demand aggressive management.
Beyond the Five Sites
Atypical femoral fracture. The drug-related stress fracture, and a discrete high-yield entity in its own right: an insufficiency-type stress fracture of the femoral lateral cortex caused by long-term suppression of bone remodelling. Prolonged bisphosphonate use, and also denosumab, lets microdamage accumulate. The ASBMR major diagnostic criteria (most of five are needed):
- Fracture in the subtrochanteric-to-supracondylar diaphysis
- Transverse or short-oblique orientation, beginning at the lateral cortex
- Minimal or no trauma
- Localised periosteal or endosteal thickening ("beaking" or flaring) of the lateral cortex
- Non-comminuted or minimally comminuted
Minor features are generalised cortical thickening, prodromal thigh or groin pain, bilaterality and delayed healing. AFFs are bilateral in a substantial proportion of patients, so always image the opposite femur.
Treating an AFF. With prodromal thigh pain and an incomplete AFF (a lateral-cortex lucent line and beaking, no complete break), stop the bisphosphonate ("drug holiday"), optimise calcium and vitamin D, and consider an anabolic agent (teriparatide) to promote healing. Proceed to prophylactic cephalomedullary nailing if pain persists or a lucent line or "dreaded black line" is present. A complete AFF is treated with cephalomedullary (intramedullary) nailing.
Spondylolysis. The classic stress fracture of the lumbar spine, and the commonest structural cause of low back pain in the adolescent athlete. It is a fatigue fracture of the pars interarticularis, most often at L5 (then L4), in young athletes doing repetitive lumbar hyperextension and rotation: cricket fast bowlers, gymnasts, dancers, divers and throwers. It may be unilateral or bilateral, and bilateral lesions can progress to spondylolisthesis.
The pain is activity-related extension low back pain, reproduced by the single-leg hyperextension (stork) test. The oblique radiograph's "Scotty dog with a collar" (lucency through the pars) is classic, but MRI is now first-line in the young: it uses no radiation, and pars marrow oedema indicates an early, active lesion with healing potential. SPECT/CT or limited CT characterises whether the defect is acute (healable) or chronic and established (terminal).
Management is activity restriction or relative rest, core and anti-extension physiotherapy, and a period of antilordotic bracing in selected cases. An early oedematous lesion can heal with rest; a chronic established defect usually will not unite but is frequently asymptomatic. Surgical repair or fusion is reserved for refractory pain or a progressive slip, which is monitored with standing lateral radiographs.
Pelvis and sacrum. Pelvic pain in endurance athletes may localise away from the femoral neck, so the MRI field must cover the symptomatic pelvis. Consider a sacral-alar stress fracture in a runner with buttock or low-back pain and normal lumbar or pelvic radiographs: MRI detects activity and CT clarifies cortical morphology.
First rib. An uncommon but important high-risk site in overhead athletes. Delayed union and the proximity of the subclavian neurovascular bundle justify cross-sectional imaging when symptoms persist or the radiograph is equivocal.
Clinical Assessment
History. The pain is activity-related and gradual in onset: at first after exercise, then during it, then at rest. It improves with rest, and there is night pain in severe cases. Ask about a recent increase in training volume, intensity or frequency, and take the risk-factor history: menstrual history, dietary intake, previous stress fractures and medications.
Examination. Inspection may be unremarkable; check for overlying swelling or warmth. Localised bony tenderness is the most sensitive clinical sign. An antalgic gait appears in severe cases, especially at the femoral neck.
Special tests. The tuning fork test has low sensitivity. The hop and fulcrum tests each reproduce the pain at a particular site:
- Hop test. Single-leg hopping reproduces the pain of a tibial stress fracture; a positive test means a stress fracture until proven otherwise.
- Fulcrum test. The patient sits with the lower legs dangling off the table edge. The examiner uses one hand as a fulcrum under the mid-thigh and applies downward pressure on the distal femur with the other; pain at the fulcrum point indicates a femoral shaft stress fracture.
Groin or anterior thigh pain, worse with weight-bearing and possibly at night, is a femoral neck stress fracture until excluded. Do not ask the patient to hop: it may displace the fracture. If it is suspected clinically, go directly to MRI, with the patient on crutches and non-weight-bearing until the fracture is excluded. A displaced femoral neck fracture in a young athlete has a high risk of AVN and is an orthopaedic emergency.
- Pain Location
- Groin, anterior thigh
- Key Examination Finding
- Pain on axial compression, positive log roll, night pain
- Urgency
- URGENT — MRI same day, NWB until excluded
- Pain Location
- Anterior shin, worse with jumping
- Key Examination Finding
- Localised anterior cortical tenderness, pain on hopping
- Urgency
- HIGH — confirm with CT/lateral X-ray for 'dreaded black line'
- Pain Location
- Dorsal midfoot, deep ache
- Key Examination Finding
- Tenderness over navicular tuberosity, pain on toe-walking
- Urgency
- HIGH — CT to confirm fracture line
- Pain Location
- Lateral foot, base of 5th MT
- Key Examination Finding
- Tenderness at proximal diaphysis, pain with inversion
- Urgency
- HIGH — distinguish from tuberosity avulsion (zone 1)
- Pain Location
- Posteromedial shin, bilateral possible
- Key Examination Finding
- Diffuse posteromedial tenderness, positive hop test
- Urgency
- LOW — MRI for grading, relative rest
- Pain Location
- Plantar first MTP, worse with toe-off
- Key Examination Finding
- Tender plantar-medial sesamoid, pain with hallux extension
- Urgency
- MODERATE — distinguish bipartite from fracture
Investigations
Radiographs. The first test, and the one not to be reassured by. Take an AP and lateral of the symptomatic bone, with site-specific views where needed (a Ferguson view for the sacrum, an oblique foot view for the 5th metatarsal). Look for periosteal reaction, cortical thickening or lucency, callus, a lucent fracture line and, at the anterior tibia, the 'dreaded black line'.
Sensitivity is only 15-30% in the first 2-3 weeks, when the film is typically normal, and improves to 50-70% by 3 weeks. A negative radiograph in a runner with focal bony tenderness therefore does not exclude a stress fracture and should prompt MRI.
MRI is the gold standard, with near 100% sensitivity for bone stress injury. STIR is oedema-sensitive, T1 shows anatomy and the fracture line, and T2 fat-sat completes the set. Marrow and periosteal oedema appear early and the fracture line late, and the Fredericson grade is read from these findings. The grade does not always correlate with symptoms, so use both to guide management.
CT has moderate sensitivity but superior cortical detail. It shows a cortical breach and confirms whether a fracture line has propagated through the cortex, so it is used where the line needs precise characterisation: the navicular, the anterior tibial cortex and the pars interarticularis. It misses early marrow oedema and is less sensitive than MRI for the early grades (Fredericson 1-2).
Bone scintigraphy has high sensitivity, approaching 100%, with focal increased uptake positive within 24-72 hours of onset. Its specificity is low, it carries a radiation dose, and MRI has largely replaced it. Do not use it first-line: MRI provides grading and anatomical detail that a bone scan cannot.
Ultrasound has a limited role. It can show periosteal reaction and cortical irregularity, but its sensitivity is low, it is operator-dependent, and it is not recommended as primary imaging.
The pathway. Four steps, from suspicion to bone health:
- Suspected stress fracture: radiograph first. It may be normal; do not be reassured.
- Radiograph normal and clinical suspicion persists: MRI, without delay.
- MRI shows a fracture line at a high-risk site: CT to characterise it (navicular, anterior tibia).
- Recurrent stress fracture or suspected RED-S: DEXA, metabolic panel and vitamin D.
The bone-health work-up. DEXA of the lumbar spine and hip, where a Z-score less than -1.0 in a young athlete is concerning. The blood panel looks for metabolic bone disease, endocrine dysfunction and nutritional deficiency: calcium, phosphate, 25-OH vitamin D, PTH, alkaline phosphatase, thyroid function, sex hormones (oestradiol or testosterone), cortisol, full blood count and ferritin.
Management Algorithm
Grade the injury, then the site. Begin with the anatomical site and symptom severity, then integrate the MRI grade: the Fredericson grade (1-4) and the site risk together set the urgency and the approach. Low-risk, low-grade injuries usually permit protected activity and staged loading. High-risk anatomy or a visible fracture line requires stricter protection, early specialist review and selective fixation.
High-risk sites on the tension side or with poor vascularity need aggressive management, and non-operative treatment often fails there. Expect 3-6 months before return at a high-risk site, and do not rush it.
The classification is the treatment. Fullerton and Snowdy divide femoral neck stress fractures by the side of the neck, with displacement as the third category.
- Location
- Superior cortex of femoral neck
- Management
- Urgent cannulated screw fixation (2-3 screws)
- Prognosis
- Good if fixed before displacement; AVN risk if displaced
- Location
- Inferior cortex of femoral neck
- Management
- NWB 4-6 weeks, repeat MRI to confirm healing; fix if progresses
- Prognosis
- Generally good; monitor for progression to tension side
- Location
- Any location, complete fracture
- Management
- Emergency ORIF (cannulated screws or sliding hip screw)
- Prognosis
- Guarded: AVN rate up to 30-60% in young adults
The tension side. The superolateral cortex, and the most dangerous stress fracture in sport, with a high quoted risk of nonunion and displacement. A displaced femoral neck fracture in a young adult is catastrophic: in a patient younger than 50 it carries a devastating risk of AVN, and of osteoarthritis. Urgent internal fixation with parallel cannulated screws or a sliding hip screw is the standard of care. Do not trial non-operative management in an athlete; this is one of the few true orthopaedic emergencies in sports medicine.
Why fix it. Fullerton and Snowdy's own cohort reported nonprogression of its tension-side fractures (see the evidence card). The argument for fixation is that the rare displacement is catastrophic and largely irreversible in a young athlete: a low-probability, high-severity decision.
The compression side. The inferomedial location is lower risk than a superolateral tension lesion, but lesion extent, pain with walking and any fracture line determine protection or fixation.
- Site Risk
- Low-risk (posterior-medial tibia) until proven otherwise
- Imaging
- MRI with Fredericson grading
- Management
- Relative rest, graded return over 6-8 weeks if low-grade
- Site Risk
- High-risk: femoral neck until excluded
- Imaging
- Urgent MRI (not X-ray — may be normal)
- Management
- If tension-side: urgent ORIF; if compression-side: NWB + repeat MRI
- Site Risk
- High-risk: tarsal navicular
- Imaging
- CT to confirm fracture line; MRI for marrow oedema
- Management
- NWB cast 6 weeks minimum; ORIF if displaced or nonunion
- Site Risk
- RED-S related — all sites at risk
- Imaging
- MRI of symptomatic site + DEXA scan + blood panel
- Management
- Multidisciplinary: nutrition, endocrinology, psychology, modified training
Complications
- Risk Sites
- Femoral neck (tension), anterior tibia
- Incidence
- Up to 30% if tension-side femoral neck treated non-operatively
- Prevention / Management
- Urgent fixation for high-risk sites; NWB until excluded
- Risk Sites
- 5th MT base (Jones), navicular, anterior tibia, sesamoid
- Incidence
- 15-30% for Jones fracture non-operative; up to 40% navicular if delayed
- Prevention / Management
- Early surgical fixation in athletes; adequate NWB duration; rule out RED-S
- Risk Sites
- Femoral neck (displaced), navicular (proximal pole)
- Incidence
- Up to 30-60% in displaced femoral neck (young adults)
- Prevention / Management
- Fix before displacement; do NOT allow WB on tension-side femoral neck
- Risk Sites
- Any site (especially tibia, metatarsals)
- Incidence
- 10-20% recurrence; up to 50% with untreated RED-S
- Prevention / Management
- RED-S screening, DEXA, vitamin D optimisation, training load management
- Risk Sites
- Anterior tibia, 5th MT, navicular, sesamoid
- Incidence
- Common in high-risk sites treated non-operatively
- Prevention / Management
- Adequate immobilisation; surgical fixation if no healing by 3-4 months
- Risk Sites
- Femoral neck (post-displacement or AVN), navicular
- Incidence
- Up to 40% after displaced femoral neck fracture
- Prevention / Management
- Fixation before displacement is the best prevention
Prevention is the most important principle in stress fracture management. It means gradual training progression, adequate nutrition and energy availability, screening for RED-S, optimising vitamin D and calcium, addressing biomechanical factors and appropriate footwear.
Outcomes and Prognosis
- Treatment
- Relative rest 6-8 weeks
- Return to Sport
- 6-10 weeks with graded programme
- Long-Term Outlook
- Excellent; full return expected
- Treatment
- Cannulated screw fixation
- Return to Sport
- 3-4 months post-fixation
- Long-Term Outlook
- Good if fixed before displacement; monitor for AVN
- Treatment
- Emergency ORIF
- Return to Sport
- 6-12 months; may not return to elite sport
- Long-Term Outlook
- Guarded: AVN rate 30-60%; risk of secondary OA
- Treatment
- Intramedullary nailing
- Return to Sport
- 3-4 months post-op
- Long-Term Outlook
- Good union rate; anterior knee pain common
- Treatment
- Strict NWB 6-8 weeks
- Return to Sport
- 4-6 months
- Long-Term Outlook
- Good if treated early; nonunion risk if poorly compliant
- Treatment
- Percutaneous IM screw
- Return to Sport
- 8-12 weeks post-op
- Long-Term Outlook
- Excellent union rate in athletes with fixation
- Treatment
- NWB + sesamoid pad 6-8 weeks
- Return to Sport
- 3-4 months
- Long-Term Outlook
- Variable; excision may be needed in refractory cases
Prognosis. Best at a low-risk site with early diagnosis (MRI grade 1-2), compliance with relative rest, adequate nutrition and no RED-S. Poorest at a high-risk site, with delayed diagnosis, displacement, untreated RED-S, recurrent fractures or low vitamin D.
Time to diagnosis is the single most important prognostic factor. A femoral neck stress fracture diagnosed and fixed before displacement has a good prognosis; a displaced fracture may end a career.
Guidelines, Registries & Global Practice
- Tibial stress fractures are the most common stress fracture worldwide in runners and military personnel
- Femoral neck stress fractures represent less than 10% of stress fractures but carry the highest morbidity
- Female athletes: 2-4 times increased risk across all sports, driven by RED-S / low energy availability
- Military recruits: Incidence of 5-10% during basic training; tibial and metatarsal sites predominate
- High-resource: Early MRI, DEXA scanning, multidisciplinary RED-S teams, surgical fixation for high-risk sites in athletes
- Limited-resource: X-ray and clinical diagnosis; prolonged casting for high-risk sites; limited access to MRI may delay diagnosis
- Universal principle: Clinical diagnosis (localised bony tenderness, activity-related pain) should trigger non-weight-bearing and imaging even when X-rays are normal
- Surgical fixation: Concentrated in specialist centres globally; percutaneous techniques have improved outcomes for Jones and navicular fractures
- Imaging Approach
- MRI gold standard; CT adjunct for navicular and tibial cortex
- High-Risk Management
- Surgical fixation for tension-side femoral neck and displaced navicular
- RED-S Approach
- IOC RED-S consensus; multidisciplinary screening mandatory
- Imaging Approach
- MRI first-line; Fredericson grading to guide return to play
- High-Risk Management
- Conservative for compression-side; operative for tension-side
- RED-S Approach
- Position stand on female athlete triad / RED-S; Z-score screening
- Imaging Approach
- MRI recommended; bone scan where MRI unavailable
- High-Risk Management
- Fix tension-side femoral neck; NWB cast for navicular
- RED-S Approach
- RED-S consensus statement; multidisciplinary team model
- Imaging Approach
- MRI-based classification; early imaging in at-risk athletes
- High-Risk Management
- Surgical fixation for high-risk sites in elite athletes
- RED-S Approach
- RED-S consensus 2014/2018 — comprehensive multisystem approach
- Imaging Approach
- CT for fracture line assessment in specific sites
- High-Risk Management
- Fixation principles: cannulated screws for femoral neck, IM screws for 5th MT
- RED-S Approach
- Nutritional and endocrine optimisation as part of fracture management
There is no dedicated arthroplasty or fracture registry for stress fractures, as most are treated non-operatively and managed in sports medicine rather than surgical settings. The evidence base is predominantly retrospective case series and expert consensus rather than randomised controlled trials. Key guidance comes from the IOC RED-S consensus statements, the ACSM Female Athlete Triad position stand, and the Fredericson MRI classification — these form the backbone of exam answers on this topic.
Record in every stress fracture presentation:
- Site and risk classification (high-risk vs low-risk)
- Imaging performed and Fredericson grade (if MRI done)
- RED-S screening status (completed / not completed / referral made)
- Weight-bearing status and activity restrictions prescribed
- Follow-up imaging plan and expected timeline
- Multidisciplinary team involvement (nutrition, psychology, endocrinology)
A missed high-risk stress fracture that progresses to a complete fracture or nonunion is a recurring source of medicolegal claims. Always document risk classification, imaging results, and the rationale for operative versus non-operative management.
Controversies & Areas of Uncertainty
Percutaneous screw fixation in athletes offers faster and more reliable return to sport, but non-operative management with NWB casting can succeed in non-athletes. The optimal screw diameter, solid vs cannulated, and need for bone graft remain debated. Refracture after screw removal is a recognised concern.
Pneumatic leg braces reduce tibial bending stress and may accelerate return to sport for posterior-medial tibial stress fractures, but evidence from randomised trials is limited. They are NOT appropriate for anterior tibial cortex fractures (tension side).
There is no universally agreed return-to-play protocol for athletes recovering from RED-S. The IOC consensus provides a framework but clear quantitative thresholds for energy availability, BMD recovery, and menstrual restoration remain debated. Some advocate a minimum 6-month period of normal menses before full training resumes.
Bisphosphonates increase BMD and may reduce stress fracture risk in military recruits, but they are NOT recommended in pre-menopausal women due to theoretical teratogenicity and the risk of atypical femoral fractures with long-term use. The role of bisphosphonates in treating (rather than preventing) stress fractures is unproven and controversial.
MCQ Practice Points
Q: What is the most important distinction in the management of stress fractures? A: High-risk vs low-risk sites. High-risk sites (femoral neck tension side, anterior tibial cortex, tarsal navicular, 5th metatarsal base, hallux sesamoid) are on the tension side or in poorly vascularised areas and require aggressive, often surgical, management. Low-risk sites (posterior-medial tibia, fibula, 2nd-4th metatarsals) are on the compression side and heal with activity modification.
Q: A runner has suspected tibial stress fracture. X-rays are normal. What is the next best investigation? A: MRI with STIR and T1 sequences. MRI is the gold standard for bone stress injuries with near 100% sensitivity. It detects marrow oedema (grade 1-2 Fredericson) weeks before X-ray changes appear and can identify fracture lines (grade 3-4). Do NOT wait for X-ray changes to appear — this delays diagnosis and risks fracture progression.
Q: A 25-year-old runner has groin pain and a tension-side femoral neck stress fracture on MRI. What is the management? A: Urgent cannulated screw fixation. Tension-side (superolateral) femoral neck stress fractures have a high rate of propagation to complete fracture and displacement. A displaced femoral neck fracture in a young adult has a 30-60% AVN rate. Fixation with 2-3 parallel cannulated screws before displacement is the standard of care. Do NOT trial non-operative management.
Q: What is RED-S and which athletes should be screened? A: Relative Energy Deficiency in Sport (formerly 'female athlete triad') is a multisystem disorder caused by low energy availability affecting metabolic rate, menstrual function (females), testosterone (males), bone health, immune function, and psychological wellbeing. Every athlete with a stress fracture should be screened for RED-S, especially endurance athletes, those with recurrent fractures, amenorrhoea, low BMI, or disordered eating patterns.
Q: What is a Jones fracture and why is it significant? A: A Jones fracture is a fracture at the metaphyseal-diaphyseal junction of the 5th metatarsal (Zone 2), distal to the tuberosity. It is significant because this region is a watershed area of vascularity with a high rate of nonunion (up to 30% non-operative). In athletes, percutaneous intramedullary screw fixation is recommended for reliable union and faster return to sport. It must be distinguished from a Zone 1 tuberosity avulsion fracture (which heals reliably non-operatively).
Q: What is the 'dreaded black line' and how is it managed? A: The 'dreaded black line' is a radiolucent line seen on lateral X-ray at the anterior tibial cortex, representing a tension-side stress fracture with cortical disruption. It is 'dreaded' because the fracture can propagate to a complete fracture under continued loading. Management in athletes is typically intramedullary nailing for reliable healing and return to sport; non-operative management with extended NWB is reserved for non-athletes but has a high failure rate.
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 24-year-old elite female distance runner presents with a 3-week history of progressive left groin pain worse with running and now present with walking. She has been amenorrhoeic for 8 months. She trains 120 km per week and has a BMI of 17.5. X-rays of the hip are reported as normal. How do you manage this patient?”
“A 22-year-old professional basketball player presents with a 6-week history of deep aching dorsal midfoot pain that worsens with running and jumping. He has been playing through pain. Examination reveals localised tenderness over the tarsal navicular. X-rays are normal. What is your diagnosis and management plan?”
Classification
- Fatigue fracture = abnormal load on normal bone (athletes, military)
- Insufficiency fracture = normal load on abnormal bone (osteoporosis, metabolic)
- High-risk sites = NAFFS: Navicular, Anterior tibia, Femoral neck (tension), Fifth MT base, Sesamoid
- Tension-side fractures propagate and need fixation; compression-side fractures heal with rest
Imaging
- X-ray: normal in 70-85% early; do NOT be reassured by a normal film
- MRI (STIR + T1): gold standard; Fredericson grade 1-4 guides management
- CT: adjunct for cortical fracture line (navicular, anterior tibia, pars)
- Bone scan: sensitive but non-specific; largely replaced by MRI
High-Risk Site Management
- Femoral neck tension side = urgent cannulated screw fixation (Fullerton classification)
- Anterior tibial cortex = IM nail in athletes; 'dreaded black line' on lateral X-ray
- Navicular = NWB cast 6-8 weeks (non-displaced); ORIF if displaced
- 5th MT Jones = percutaneous screw in athletes; NWB cast in non-athletes
RED-S
- Formerly 'female athlete triad'; affects males and females
- Low energy availability causes hypothalamic suppression, hormonal disruption, low BMD
- Screen every stress fracture patient: diet, menses/testosterone, BMI, training load
- DEXA Z-score less than -1.0 in young athlete = investigate further
Key Exam Answers
- Normal X-ray does NOT exclude stress fracture — proceed to MRI
- Tension-side femoral neck fracture = operate, do NOT trial conservative
- Fredericson grade 4 = fracture line visible on both STIR and T1 MRI
- Greater than 10% weekly training volume increase is a key risk factor for recurrence
Evidence Base and Key Trials
Tibial stress reaction in runners. Correlation of clinical symptoms and scintigraphy with a new magnetic resonance imaging grading system
- FOURTEEN runners with 18 symptomatic legs, each imaged within 10 days by radiograph, technetium bone scan and MRI - the grading system everyone cites rests on this sample
- Proposed the continuum that the grades describe: periosteal oedema, then progressive marrow involvement, then frank cortical stress fracture
- MRI findings correlated with the established technetium grading system in 14 of the 18 legs and defined the location and extent of injury more precisely
- Clinical features correlating with more severe injury were pain with daily ambulation, localised tibial tenderness, and pain on direct or indirect percussion
- The paper's recommendation is MRI OVER BONE SCAN when grading is clinically warranted - more accurate correlation with symptoms, no ionising radiation and substantially shorter imaging time than three-phase scintigraphy
American College of Sports Medicine position stand: the female athlete triad
- Formalised the Female Athlete Triad as low energy availability, menstrual dysfunction, and low BMD
- Established screening guidelines for at-risk athletes including DEXA criteria
- Z-score less than -1.0 at lumbar spine or hip in a young athlete warrants further investigation
- Energy availability below 30 kcal/kg lean body mass per day disrupts luteinising hormone pulsatility
Low-risk stress fractures
- Classified stress fractures into high-risk and low-risk sites based on biomechanics and healing potential
- High-risk sites: femoral neck (tension), anterior tibial cortex, tarsal navicular, 5th metatarsal base, sesamoid
- Low-risk sites: posterior-medial tibia, fibula, 2nd-4th metatarsals, calcaneus, femoral shaft
- Tension-side fractures propagate and require aggressive management; compression-side fractures heal with rest
Femoral neck stress fractures
- A 4-year PROSPECTIVE study - not a retrospective series - of 54 femoral neck stress fractures in 49 patients, identified within a denominator of 1,049 stress fractures of all types
- Produced the classification still used, dividing femoral neck stress fractures by site into tension-side (superolateral) and compression-side (inferomedial), with displacement as the third category
- Its own headline caveat is easily lost: among the differences the authors noted from earlier reports was the NONPROGRESSION of tension-side fractures in this cohort, alongside differences in racial diversity and return to function
- Compression-side fractures were managed non-operatively with restricted weight-bearing and close radiographic monitoring
Fractures of the base of the fifth metatarsal distal to the tuberosity: classification and guidelines for non-surgical and surgical management
- 46 fractures of the fifth metatarsal base distal to the tuberosity, followed a mean of 40 months, classified radiographically into acute (narrow line, no intramedullary sclerosis), delayed union (widened line with sclerosis) and nonunion (medullary canal obliterated by sclerotic bone)
- The central result is about WEIGHT-BEARING, not about surgery: of 25 acute fractures, 15 were treated in a non-weight-bearing toe-to-knee cast and 14 of those healed at a mean of 7 weeks, whereas of the 10 treated by various WEIGHT-BEARING methods only 4 united
- Delayed unions did poorly in plaster: of 10 so treated, 7 healed but took a mean of 15.1 months and 3 required grafting
- Nonunions did well with surgery: 8 of 9 healed at a mean of 3 months after medullary curettage and bone grafting, and of 20 fractures grafted overall, 19 healed completely
- The paper reports NO 30% nonunion rate for cast treatment and does not recommend primary screw fixation for acute fractures - that is a later practice position driven by speed of return in athletes, not by this data