Progressive Shin Pain and Low Energy Availability in a Distance Runner

Learning objectives#

• Distinguish a tibial bone stress injury from diffuse medial tibial stress syndrome, exertional compartment syndrome, vascular disease, nerve entrapment, infection, and tumor.
• Recognize when normal early radiographs should be followed by MRI rather than by continued impact training.
• Assess low energy availability as a physiologic mismatch that can affect athletes of any body size, gender, competition level, or eating-disorder status.
• Integrate menstrual, reproductive, endocrine, bone, mental-health, nutrition, training, sleep, and social information without turning one biomarker into a diagnosis.
• Classify anatomic risk and use pain, function, imaging, and contributing-factor recovery to guide sport participation.
• Build a criteria-based return-to-running plan that protects bone while preserving identity, conditioning, and shared decision making.

Initial presentation#

A 27-year-old recreational distance runner asks for a sports-medicine appointment because the inside of her left shin has hurt for seven weeks. She began training for her first marathon after several years of shorter road races. Over three months, weekly running volume rose from four moderate sessions to six sessions that included a long run, hill repeats, and a faster group workout. A retail job keeps her standing most days. She has not had a single fall or blow.

At first, a broad ache appeared near the end of long runs and settled by the next morning. She assumed it was "shin splints" and changed shoes. During the next month, the painful area became small enough to cover with one fingertip. It now hurts during the first few minutes of running, eases slightly, then becomes sharper. It aches after work and woke her twice this week. She has stopped jumping but continues easy running because her marathon entry was expensive and friends are fundraising with her.

She also reports fatigue, feeling cold at work, declining workout pace, and two minor respiratory illnesses. Her last spontaneous menstrual period was eight months ago. Before that, cycles became progressively farther apart after she stopped combined hormonal contraception. A clinician previously said missing periods was common in runners and offered to restart the contraceptive. She declined because contraception is not currently needed. She has not been pregnant and has no hot flashes, galactorrhea, hirsutism, severe acne, headache, or visual change.

Food history is obtained without moral labels. She eats a varied vegetarian diet and does not report vomiting, laxatives, diet pills, binge episodes, or a fixed goal weight. Her appetite falls after intense training, she often runs before breakfast, and work breaks are unpredictable. Online advice led her to reduce fats and avoid eating late. She has lost several kilograms during the training block, but she does not know whether this was intended. She worries that increasing food will make her slower and says a group leader recently praised runners who looked "race lean."

Temperature is normal. Resting pulse is 48 per minute, blood pressure is 102/66 mm Hg lying and lower on standing, with brief lightheadedness. She is alert and not acutely ill. Body mass index falls within a commonly labeled normal range, but no one uses that fact to rule out inadequate energy availability. Cardiac examination is regular, lungs are clear, and there is no edema.

The left tibia has a focal area of marked posteromedial tenderness in the middle-to-distal third. There is no redness, warmth, mass, fluctuance, or diffuse swelling. A single-leg hop causes immediate focal pain and is stopped rather than repeated. Walking in the room is comfortable, but brisk hallway walking produces a mild ache. Calf compartments are soft at rest. Pulses and neurologic findings are normal. Hip abductor and calf endurance are lower than expected bilaterally, and the left side is more symptomatic. The opposite leg and foot are examined because bone stress injuries and load contributors may be multifocal.

Problem representation#

This is an adult endurance athlete with a rapid increase in impact load, progressive focal posteromedial tibial pain, night symptoms, focal bony tenderness, and pain on a loading test. She also has prolonged secondary amenorrhea, weight change, fatigue, orthostatic symptoms, resting bradycardia, under-fueling opportunities, and performance decline. There is no acute trauma, infection pattern, neurovascular deficit, or exertional-only tightness that resolves rapidly with rest.

The leading representation is a tibial bone stress injury arising from load exceeding bone remodeling capacity, with clinically important low energy availability and hypothalamic menstrual suppression as likely contributors. The focal posteromedial site is generally lower risk than the anterior tibial cortex, but risk cannot be assigned solely from palpation. Imaging must define the lesion and exclude a fracture line or high-risk location.

The case has two inseparable problems. Protecting the tibia without restoring energy availability invites delayed healing and recurrence. Labeling every athlete with low energy availability as having an eating disorder can create shame and miss structural barriers such as work schedules, food cost, appetite, dietary knowledge, or training culture. Both the bone and the physiologic context require precise, respectful assessment.

Prioritized differential#

1. Posteromedial tibial bone stress injury#

Reasoning for: Focal tenderness, progressive pain earlier in runs, pain after activity and at night, and pain with hopping fit a continuum of stress reaction through stress fracture. The rapid training increase, limited recovery, high occupational loading, menstrual suppression, and probable low energy availability raise susceptibility. Early radiographs may be normal.

Risk question: Posteromedial tibial compression-side injuries generally heal more predictably than anterior-cortex tension-side lesions. Anterior focal tenderness, an anterior cortical line, or persistent radiographic abnormality would increase nonunion and completion-fracture concern and demand more restrictive specialist management.

2. Medial tibial stress syndrome#

This common running-related diagnosis can cause exercise-induced pain along a broader posteromedial border. Diffuse tenderness over a longer segment favors it. The increasingly focal site, night ache, and hop pain make a bone stress injury more likely here. The entities may share load contributors and exist on a continuum, so the label should follow the pattern and imaging rather than a reflex use of "shin splints."

3. Chronic exertional compartment syndrome#

Compartment syndrome typically produces reproducible pressure, cramping, paresthesia, or weakness after a predictable exercise duration, then improves after stopping. The examination at rest can be normal. This runner's focal bony tenderness and persistent postexercise or night pain argue against it. If symptoms instead included exertional foot slap, numbness, or tight compartments with a clock-like onset, exercise-provoked assessment and specialist testing would become relevant.

4. Vascular or neurologic exertional disease#

Popliteal artery entrapment, endofibrosis, arterial disease, venous thrombosis, lumbar radiculopathy, and peripheral nerve entrapment can cause leg pain. Pulse change with provocative positions, exertional coldness, color change, swelling, paresthesia, back pain, or focal neurologic deficits would redirect testing. Normal pulses at rest do not exclude all exertional vascular disorders, but this presentation is not primarily ischemic.

5. Muscle, tendon, or fascial injury#

Soleus strain, tibialis posterior injury, fascial traction, and calf overload can cause posteromedial symptoms. Pain with resisted muscle testing, soft-tissue rather than bony tenderness, and a different loading pattern would support them. They are less coherent with the focal tibial pain and broader physiologic risk picture.

6. Infection, inflammatory disease, or bone tumor#

Fever, progressive rest pain unrelated to load, warmth, swelling, systemic illness, unexplained anemia, or an aggressive radiographic lesion would demand urgent investigation. Night pain is not automatically malignant; in this case it appears after a clear progressive load pattern. Yet persistence despite unloading or imaging that does not fit a stress injury must reopen this branch.

7. Endocrine and reproductive alternatives to functional hypothalamic amenorrhea#

Pregnancy, thyroid disease, hyperprolactinemia, primary ovarian insufficiency, polycystic ovary syndrome, pituitary disease, chronic systemic illness, and medication effects can alter cycles. Functional hypothalamic amenorrhea is a diagnosis made after appropriate exclusion and within the clinical energy-stress context. Hormonal contraception can obscure the underlying cycle and must be included in the timeline.

8. Low energy availability with or without an eating disorder#

Low energy availability describes insufficient dietary energy remaining for normal physiologic functions after exercise demands. It may be unintentional, intentionally performance driven, or part of disordered eating or a diagnosable eating disorder. The athlete's restrictive rules, fear of slowing, weight change, and external comments warrant careful assessment, but a diagnosis cannot be inferred from sport, body size, or one screening score.

Focused history and examination#

The pain history maps the exact point, length of tenderness, relation to impact, time to onset, behavior after stopping, night pain, walking pain, and change over weeks. The clinician asks about previous bone stress injuries, fractures, low bone density, surgery, foot or leg biomechanics, training surfaces, hills, speed work, footwear changes, strength training, and whether rest days are true low-load days. Training data are used to understand exposure, not to identify a universal safe percentage increase.

Energy availability cannot be calculated accurately from a casual food diary. The assessment instead combines multiple domains:

• meal and snack timing around training, work, school, sleep, and travel;
• food access, cost, cooking facilities, dietary pattern, allergies, gastrointestinal symptoms, and appetite;
• intentional restriction, fasting, avoided food groups, body checking, guilt, bingeing, vomiting, laxative or diuretic use, and compulsive exercise;
• weight trajectory and growth history rather than a single measurement;
• menstrual cycle history, hormonal medication timeline, pregnancy possibility, fertility goals, and symptoms of alternate endocrine disease;
• fatigue, cold intolerance, recurrent illness, sleep change, low mood, anxiety, irritability, libido, sexual function, concentration, and performance;
• pressure from coaches, peers, social media, team weigh-ins, uniforms, sponsorship, or weight-sensitive sport culture;
• previous nutrition care and whether the athlete felt blamed or excluded.

The mental-health history includes depression, anxiety, self-harm, suicidality, trauma, obsessive features, substance use, and the role of exercise in emotional regulation. A questionnaire can support conversation but cannot rule an eating disorder in or out. If an eating disorder is suspected, age-appropriate specialist assessment is arranged promptly.

Examination includes temperature, resting and orthostatic pulse and blood pressure, hydration, mucosal and skin findings, thyroid and cardiac assessment, and features of systemic illness. The lower-limb assessment looks at gait, focal bone tenderness, swelling, alignment, ankle and foot function, calf capacity, hip and trunk strength, and neurovascular status. High-impact provocation is used sparingly; repeated hopping is unnecessary when one attempt clearly reproduces focal bone pain.

Serious physiologic instability is actively sought: syncope, chest pain, severe bradycardia with symptoms, hypotension, orthostatic intolerance, electrolyte disturbance, hypoglycemia, dehydration, severe malnutrition, uncontrolled purging, acute suicidality, or rapid clinical decline. Those findings change the setting of care from outpatient sports management to urgent medical stabilization.

Diagnostic strategy#

Image the bone according to risk and clinical probability#

Initial tibia and fibula radiographs are reasonable because they can show a fracture line, cortical reaction, another bone lesion, or an alternative diagnosis. A normal result early in the course does not exclude a bone stress injury. In a runner with focal bony tenderness and progressive pain, continued impact while waiting for a radiographic change is not a diagnostic test.

ACR criteria support MRI of the area without contrast as the usual next study when radiographs are negative or indeterminate and a stress fracture remains suspected. MRI detects marrow and periosteal edema, can show a fracture line, identifies site and extent, and avoids ionizing radiation. Contrast is not routinely needed for a straightforward bone stress question. CT can characterize cortex in selected cases, while bone scintigraphy has less specificity and uses radiation. The choice changes if infection or tumor is suspected.

Assess bone and energy contributors without ordering a ritual panel#

Testing is individualized. A pregnancy test is obtained when biologically possible and relevant. Blood count, ferritin and iron indices, metabolic measures, calcium, phosphate, alkaline phosphatase, vitamin D, thyroid-stimulating hormone, and selected endocrine tests can identify anemia, iron deficiency, metabolic disturbance, thyroid disease, or another contributor. Menstrual evaluation may include prolactin, gonadotropins, estradiol, and androgen-related tests depending on history and examination. Results are interpreted in context; a single "normal" reproductive hormone value does not prove adequate energy availability.

Screening for celiac disease or other malabsorption is guided by gastrointestinal symptoms, iron deficiency, family history, and overall pattern. Broad hormone, autoimmune, and nutrient panels can produce incidental results without improving care. Supplements are not used to compensate for an unexamined dietary deficit.

The Endocrine Society recommends bone-density assessment for prolonged amenorrhea and earlier when severe nutritional deficiency, energy deficit, or skeletal fragility is suspected. This athlete has both amenorrhea and a bone stress injury, so dual-energy X-ray absorptiometry is appropriate. Interpretation uses age- and sex-appropriate standards and the full clinical context. A value outside the expected range changes risk management, but a value within range does not make the current injury harmless.

Use REDs tools as structured aids, not automatic verdicts#

The IOC REDs Clinical Assessment Tool Version 2 organizes screening, severity and risk assessment, and physician-led diagnosis with multidisciplinary input. It includes serious medical indicators and sport-participation guidance. It is not a self-administered clearance certificate and has evolving validation. The clinician uses it to make domains visible, then makes an individualized decision with the athlete and relevant specialists.

Progressive results and interpretation#

Plain radiographs show no fracture line, cortical lucency, or aggressive lesion. There is subtle posteromedial cortical thickening that could reflect load adaptation but is not diagnostic. The normal-looking study does not reconcile the focal findings, so impact running is stopped and MRI is arranged.

MRI demonstrates periosteal and marrow edema along the posteromedial mid-to-distal tibia without an anterior-cortex lesion or visible fracture line. There is no soft-tissue mass, marrow replacement, or collection. The pattern is a moderate-grade posteromedial tibial bone stress injury at a generally lower-risk compression site. Lower risk is not no risk; pain with walking and the physiologic contributors still require protection.

Blood count shows no anemia, but iron stores are low. Electrolytes, renal measures, glucose, calcium, phosphate, and thyroid-stimulating hormone are not concerning. Pregnancy testing is negative. Prolactin is not elevated. Gonadotropin and estradiol patterns, interpreted with the history, support hypothalamic suppression rather than ovarian failure, while no clinical or biochemical pattern strongly suggests hyperandrogenism. These findings support functional hypothalamic amenorrhea after alternative causes have been proportionately considered.

Bone-density imaging shows a Z-score below the expected range for age at one measured site, without an established fragility fracture history. The number is not used alone to diagnose osteoporosis or predict healing. Combined with amenorrhea, low iron stores, a bone stress injury, and under-fueling, it strengthens the need for energy restoration, bone-health follow-up, and cautious return to impact.

A sports dietitian's detailed assessment identifies a large gap between training and intake, especially before morning runs, through long shifts, and after evening sessions. The athlete does not meet criteria for a specific eating disorder in the initial specialist assessment, but she has rigid food rules and anxiety about weight gain that deserve psychological support. The team records problematic low energy availability with functional hypothalamic amenorrhea and impaired bone health, not "noncompliant runner."

When training pauses, her distress rises. Running is her main social connection and a key coping strategy. This does not mean the medical restriction should be abandoned. It means treatment must provide safe conditioning options, social continuity, mental-health support, and a transparent path back to sport.

Management plan#

Protect the tibia according to symptoms and site#

Impact running, jumping, and painful occupational loading stop initially. Because brisk walking causes pain, temporary protected weight bearing and a walking aid are considered, with the exact level determined by the sports physician and physiotherapist. The goal is pain-free daily mobility, not punishment or complete inactivity. Immobilization is not automatic for every posteromedial injury, and high-risk anterior cortical lesions would require a different orthopedic plan.

Pain management is individualized and avoids masking pain to continue running. Exact medicine choices depend on medical history and the treating team. Repeated use of anti-inflammatory medicine simply to train through bone pain is discouraged. Sleep, safe alternative movement, and practical work modification support recovery.

Cross-training is allowed only if the chosen activity is pain free at the injury site and compatible with physiologic stability and energy restoration. Depending on the person, this might include carefully prescribed pool or cycle work, but exercise is reduced further when it perpetuates an energy deficit, compulsive behavior, or symptoms. Strength work begins with nonpainful trunk, hip, and upper-body tasks, then progresses to calf and lower-limb loading when clinically appropriate.

Restore energy availability and nutrient sufficiency#

The sports dietitian and athlete build an accessible plan that increases total energy and supports timing before, during, and after training as activity returns. It includes adequate carbohydrate, protein, fat, calcium, vitamin D, iron, and dietary variety without labeling ordinary foods as clean or bad. A vegetarian pattern can fully support sport, but iron, protein quality, calcium, vitamin B12, and energy density need deliberate attention based on actual intake.

No universal calorie target or weight number is imposed in this educational case. Needs change with body size, training, healing, work, and recovery. Weight may rise during restoration, remain stable, or change in another way; physiologic and psychological response matters more than an arbitrary appearance. Iron or vitamin supplementation follows confirmed need, dietary assessment, medical contraindications, and current product guidance, with no dosing schedule provided here.

Structural barriers are treated as causes. The team helps secure predictable work breaks, portable food, affordable options, access to a refrigerator, and a plan for early sessions. The running group is told only what the athlete authorizes. A coach can support adjusted training but does not receive private reproductive or mental-health information without consent.

Address menstrual and bone health without masking the signal#

The first-line aim in functional hypothalamic amenorrhea is correction of the energy imbalance through nutrition, modified exercise, and psychological support where helpful. Menstrual recovery may lag behind other improvements. Hormonal contraception can be appropriate for contraception, bleeding control, or another patient-centered indication, but it is not prescribed solely to create withdrawal bleeding or presented as proof that bone physiology has recovered.

If menses do not return after a reasonable period of comprehensive treatment, an endocrinologist considers guideline-supported options in the person's full context. Fertility goals are discussed sensitively. Pregnancy can occur before the first recognized menstrual period, so contraception counseling remains relevant when pregnancy is possible and not desired.

Bone health care includes progressive resistance and impact loading only when the tibia and overall medical state permit, adequate nutrition, avoidance of smoking, and individualized alcohol counseling. Repeat bone-density testing is not scheduled so frequently that measurement noise is mistaken for change. The interval follows specialist guidance, risk, and whether results will alter care.

Treat mental health and sport culture as part of recovery#

Psychological care addresses anxiety about food and weight, identity loss, perfectionism, mood, compulsive exercise, and coping outside running. If an eating disorder emerges, specialist evidence-based care takes priority and the sport plan is coordinated with it. Immediate care is arranged for suicidality or medical instability.

The athlete, clinician, dietitian, physiotherapist, and, with permission, coach agree on one participation message. Conflicting advice such as "rest the bone" from one clinician and "maintain race fitness" from another undermines safety. The reason for temporary restriction, criteria for progression, and the next assessment date are written clearly.

Escalation, referral, and safety net#

Urgent orthopedic or sports-medicine escalation is needed for inability to bear weight, a visible fracture line, anterior tibial cortex involvement, pain that rapidly worsens despite unloading, new deformity, or concern for completion fracture. Femoral neck, navicular, sacral, and other high-risk bone stress sites require their own urgent pathways. Fever, redness, progressive swelling, a mass, severe unremitting rest pain, or systemic illness triggers investigation for infection, inflammatory disease, or tumor.

Medical escalation is immediate for syncope, chest pain, concerning arrhythmia, severe or symptomatic bradycardia, hypotension, marked orthostatic change, dehydration, hypoglycemia, significant electrolyte abnormality, uncontrolled purging, severe malnutrition, acute suicidality, or inability to maintain safe intake. A normal-range BMI does not prevent escalation when physiology is unstable.

Referral is multidisciplinary but coordinated. Sports medicine owns injury classification and participation decisions. Radiology characterizes site and grade. A sports dietitian addresses energy and nutrient restoration. Physiotherapy restores loading capacity and biomechanics. Endocrinology or gynecology evaluates persistent amenorrhea, bone health, and reproductive alternatives. Mental-health and eating-disorder specialists address psychological risk where present. Primary care integrates the whole person and prevents fragmented testing.

The athlete returns promptly for increasing focal pain, new pain at rest, pain with ordinary walking, swelling, another focal bone site, fainting, palpitations, severe dizziness, inability to eat, vomiting or purging, rapidly worsening mood, or thoughts of self-harm. The plan states exactly which clinic and urgent service to use.

Communication, shared decisions, and equity#

The clinician explains the connected diagnosis: "The MRI shows that the shin bone has been injured by repeated load. It has not formed a complete fracture line, which is good, but it needs protection. Your missing periods, fatigue, nutrition pattern, and bone-density result suggest that too little energy has been available for normal body functions. Healing means reducing impact now and increasing the resources your body has for bone and hormone recovery."

The athlete is not told that she caused the injury by lacking discipline. Endurance culture often rewards ignoring hunger, pain, menstrual change, and fatigue. Training apps can turn recovery into failure, and comments from coaches or clinicians can reinforce restriction. Naming these pressures shifts responsibility toward a solvable system without removing personal agency.

Low energy availability can affect women, men, transgender athletes, nonbinary athletes, disabled athletes, larger-bodied athletes, and people at every level of competition. Menstrual history is relevant when a person menstruates, not because of a gender assumption. For people receiving gender-affirming hormones, endocrine and bone assessment is individualized with knowledgeable care. BMI is not used as a gate to concern or treatment.

Food recommendations must fit culture, religion, allergies, finances, housing, work, and sensory needs. Advising frequent specialty products to someone without reliable food access is not a plan. Vegetarian and vegan patterns are not blamed; the team identifies whether actual intake meets energy and nutrient needs.

Shared decisions include the athlete's goals, but medical risk boundaries are explicit. The team acknowledges the financial and emotional loss of missing a marathon and helps with deferral documentation. They preserve involvement through volunteering or nonrunning group activities if she wants. The return pathway is presented as active rehabilitation, not indefinite removal from identity.

Follow-up and contingencies#

Early visits reassess pain with walking, focal tenderness, mobility, sleep, alternative training, energy intake, orthostatic symptoms, pulse, mood, and adherence barriers. Laboratory retesting is targeted to abnormalities such as iron deficiency and to questions that can change management. Menstrual recovery, libido, warmth, sleep, energy, concentration, and performance are useful longitudinal signals but none alone certifies recovery.

Before return to running, the clinician considers five domains supported by the 2024 return-to-running scoping review and broader consensus:

1. pain-free walking and daily activities;
2. resolution of focal bony tenderness when relevant to the injury risk category;
3. evidence of adequate healing, with radiologic healing particularly important for high-risk injuries;
4. restored strength, balance, calf capacity, and functional loading tolerance;
5. meaningful correction of training, nutrition, endocrine, biomechanical, and psychological contributors.

The first running exposure uses short, easy walk-run intervals on alternate days or another individualized schedule. Distance or time increases before speed, hills, and clustered hard days. Only one major load variable changes at a time. Symptoms during the session, later that day, and the next morning guide progression. Pain at the focal site leads to stopping, reassessment, and regression rather than analgesic-supported completion.

No universal weekly percentage guarantees safety. Bone site, MRI grade, time away, menstrual and energy recovery, prior injuries, strength, surface, footwear, pace, and the athlete's history alter progression. High-risk sites require specialist and sometimes radiographic confirmation before impact.

Four contingency branches remain visible:

• Pain resolves and physiologic recovery progresses: Begin criteria-based running while continuing nutrition, strength, and menstrual or endocrine follow-up.
• Pain persists despite appropriate unloading: Reassess diagnosis, site risk, adherence barriers, imaging, infection or tumor clues, and whether everyday work is still overloading the tibia.
• A new bone stress injury appears: Stop impact, search for persistent low energy availability, low bone density, endocrine or gastrointestinal disease, training error, and an incomplete first rehabilitation.
• Restriction anxiety or disordered eating intensifies: Increase mental-health and eating-disorder support, reassess medical stability, and avoid using exercise permission as a reward for weight or food behavior.

Long-term prevention includes adequate fueling through all training phases, planned recovery, resistance training, gradual changes in impact, symptom-responsive coaching, sleep, and a culture in which menstrual or sexual-function change and recurrent injury prompt care. The goal is durable participation, not a single race completion.

Reasoning traps and alternative pathways#

• Calling all runner shin pain "shin splints": Focal tenderness, progressive load pain, night symptoms, and walking pain should raise bone stress concern.
• Using a normal radiograph as clearance: Early bone stress injuries may be radiographically occult. MRI can change protection and risk classification.
• Performing repeated hop tests: One clearly painful loading test is enough; repeated provocation does not make the diagnosis more valid.
• Equating normal BMI with adequate energy: Energy availability concerns the relationship between intake, exercise, and physiology, not a body-size category.
• Equating REDs with an eating disorder: They can coexist, but either can occur without the other. Both deserve assessment without stigma.
• Normalizing amenorrhea as fitness: Menstrual loss is a clinical signal and requires pregnancy and endocrine reasoning as well as energy assessment.
• Treating a withdrawal bleed as recovery: Hormonal contraception may mask spontaneous cycle status and does not by itself restore the underlying energy state.
• Prescribing rest without treating identity and access: A runner may continue secretly if the plan ignores conditioning, community, work, finances, and mental health.
• Returning by calendar alone: Time matters, but pain-free function, injury site, healing, strength, and contributor correction matter too.
• Fixing biomechanics while under-fueling continues: Gait and strength can be useful, but they cannot substitute for sufficient energy and bone-health care.

An alternative pathway would apply if MRI showed an anterior tibial cortical fracture line. The lesion would be treated as higher risk, with urgent orthopedic input, more restrictive loading, and imaging-supported healing decisions. A femoral neck pain pattern would require immediate cessation of weight bearing and urgent imaging because displacement can be catastrophic.

Diffuse tenderness without MRI bone injury would support medial tibial stress syndrome and a graded load-rehabilitation plan. Reproducible exertional tightness with numbness and rapid relief would raise chronic exertional compartment syndrome. Exertional loss of pulse or foot coolness would trigger vascular assessment. An aggressive bone lesion would move oncology or infection evaluation to the center.

If endocrine testing showed hyperprolactinemia, thyroid disease, ovarian insufficiency, or pregnancy, that condition would be addressed while bone protection continued. If a specialist assessment diagnosed an eating disorder, medical and psychological treatment would follow that guideline, and sport participation would be subordinated to medical stability and recovery.

Evidence limits and what could change#

Bone stress injury terminology and MRI grading systems vary, and imaging severity does not map perfectly to symptoms or recovery time. The 2025 international Delphi consensus improves shared language, but many return-to-sport recommendations still rely on observational data, expert consensus, and heterogeneous athlete groups. A site-specific, athlete-specific plan is more defensible than a universal timetable.

The 2023 IOC REDs consensus and CAT2 broaden physiologic assessment and offer structured risk categories. The tool's real-world validation continues to develop, and indicators differ across sex, age, sport, disability, ethnicity, hormonal medication, and access to testing. A traffic-light category should support clinical reasoning, not replace it.

Menstrual dysfunction and bone stress injury can strongly support an energy-deficiency formulation, but no single laboratory value diagnoses low energy availability. Direct calculation outside controlled research is difficult. Conversely, intentional restriction is not required; an athlete can under-fuel through schedule, appetite, misinformation, food insecurity, gastrointestinal problems, or an unrecognized increase in expenditure.

The Endocrine Society guideline addresses functional hypothalamic amenorrhea, while the Female Athlete Triad and REDs frameworks overlap but are not identical. Hormonal and bone treatments require specialist interpretation, fertility goals, contraindications, and updated product information. This case avoids drug doses and does not treat a monthly bleed as the sole outcome.

Return-to-running evidence emphasizes pain-free walking, resolution of bony tenderness where appropriate, strength and functional testing, healing, and correction of contributing factors. The exact sequence, surface, interval length, and progression rate remain incompletely tested. Future work may refine biomarkers, wearable-load measures, imaging prognostics, and sex- and gender-inclusive risk models.

Key points#

• Progressive focal tibial pain, night ache, and pain with loading require bone stress reasoning even when initial radiographs are normal.
• MRI can identify a stress reaction, fracture line, anatomic site, and alternative lesion and can separate lower-risk from high-risk pathways.
• Low energy availability can be unintentional, can occur at any body size, and is not synonymous with an eating disorder.
• Amenorrhea is not a normal badge of endurance fitness; pregnancy and alternative endocrine causes must be assessed before functional hypothalamic suppression is concluded.
• Treatment integrates load protection, sufficient energy and nutrients, mental health, bone and reproductive care, strength, and structural access barriers.
• Return to running follows pain-free function, healing, loading capacity, and correction of contributors rather than a race date or one weekly percentage rule.

Sources#

1. International Olympic Committee: 2023 Consensus Statement on Relative Energy Deficiency in Sport
2. International Olympic Committee: REDs Clinical Assessment Tool Version 2 Development and Validation
3. American College of Radiology: Appropriateness Criteria for Stress Fracture
4. International Delphi Consensus on Bone Stress Injuries in Athletes
5. Criteria and Guidelines for Returning to Running Following a Tibial Bone Stress Injury
6. Female Athlete Triad Coalition: Consensus Statement on Treatment and Return to Play
7. Endocrine Society: Functional Hypothalamic Amenorrhea Guideline
8. American College of Sports Medicine: Position Stand on the Female Athlete Triad
9. International Association of Athletics Federations: Consensus Statement on Nutrition for Athletics
10. NICE NG69: Eating Disorders Recognition and Treatment