Case Study – Femoral Shaft Stress Reaction in a Competitive Runner
Clinical History:
24-year-old female US college runner presenting with left groin and anterior thigh pain radiating towards the knee.
She was training for collegiate competition and had recently increased her weekly running volume from approximately 30 km to 40 km.
Her training included a varied programme consisting of interval sessions, sprint work, and steady-state running.
Symptoms were particularly exacerbated during higher-speed track sessions.
Pain initially presented in the left groin crease and progressively radiated into the anterior thigh. She also reported a dull ache following training sessions and night pain.
An MRI scan of the hips performed in the USA prior to review was reported as normal.
Past Medical Hx:
- Previous history of disordered eating (ages 18–19), lasting approximately one year
- Currently well, with stable weight and adequate nutritional intake
- Regular menstrual cycles
Drug Hx:
- Vitamin supplementation
- No other medications
Exercise Hx:
- High-level collegiate runner
- Structured strength and conditioning programme (multiple gym sessions per week)
- Uses a variety of footwear including carbon-plated racing shoes and training spikes
- Recent increase in use of carbon-plated footwear
Examination
- Pain localised primarily to the anterior mid-thigh at time of presentation
- No focal tenderness on palpation
- No bruising or soft tissue abnormality
- Hip examination unremarkable
- No obvious biomechanical abnormalities in foot posture or gait
Initial Imaging
Previous MRI hip scan done in USA of left hip only: Mild labral changes
Differential Diagnosis and Clinical Reasoning
Hip Joint Pathology (Labral Injury / Hip Sprain)
Hip joint pathology can commonly refer pain into the groin and anterior thigh, sometimes extending to the knee. However, normal hip MRI imaging and lack of mechanical hip symptoms made this less likely.
Inguinal Pathology (Femoral Hernia / Obturator Nerve Entrapment)
Inguinal-related conditions may present with groin pain radiating into the anterior thigh. However, absence of palpable findings and the progression of symptoms into the mid-thigh reduced the likelihood of this diagnosis.
Lateral Cutaneous Nerve Entrapment
Typically presents with sensory disturbance or pain along the lateral thigh. This was inconsistent with the patient’s anterior thigh pain distribution.
Femoral Shaft Bone Stress Injury
Given:
- Progressive increase in training load
- Pain localised to the anterior thigh
- Night pain and post-exercise ache
- Normal hip imaging
A femoral stress injury became the leading diagnosis, later confirmed on MRI.
Further Imaging
Given ongoing symptoms and localisation to the thigh, an MRI of the femur was arranged.
MRI Findings:
- Mid-shaft femoral bone stress reaction
Most mid shaft femoral stress reactions will show a periosteal reaction on MRI.
X-rays can show mild cortical thickening of the but can often be inconclusive.
Axial fluid sequence MRI is the best imaging modality for this.
Diagnosis
Mid-shaft femoral bone stress reaction
Management
- Immediate reduction in running load
- Cessation of high-impact and high-speed training
- Low impact cross-training introduced
- Gradual return-to-run, load management programme planned
Medical and Metabolic Workup
Blood tests revealed:
- Low T3 levels (suggestive of low energy availability)
- Elevated prolactin
- Suppressed LH, FSH, and estradiol
- Ferritin: 20 (low)
- Haemoglobin: 11 (borderline anaemia)
- Vitamin D: Normal
Interventions
- Iron supplementation initiated
- Nutritional optimisation advised
- Monitoring of menstrual cycle using tracking (e.g. Flow app)
- Ongoing review of energy availability
Discussion and Key Points
Femoral shaft stress injuries are an important and often under-recognised cause of thigh pain in runners, particularly:
- High-performance athletes
- Female runners
- Individuals with increased training loads
- Athletes performing high-speed or track-based training
Key Clinical Learning Points:
- Pain location matters:
Anterior thigh pain, particularly with radiation towards the knee, should raise suspicion of femoral shaft pathology. - Do not rely solely on hip imaging:
Hip pathology can refer pain distally, but normal hip MRI does not exclude femoral stress injury.
→ Always consider femoral MRI if symptoms persist. - Track running biomechanics:
Repetitive loading, particularly when running bends, may increase unilateral femoral stress. - Energy availability is critical:
Even in athletes with:- Normal BMI
- Regular menstruation
- Subclinical Relative Energy Deficiency in Sport (RED-S) may still be present.
- Blood markers can provide early clues:
- Low T3 = sensitive indicator of under-fuelling
- Hormonal suppression may precede menstrual disturbance
- Footwear considerations:
Increased use of carbon-plated shoes may alter loading patterns and contribute to stress injury risk.
Take Home Message
In runners presenting with groin pain radiating into the thigh or knee:
- Always consider femoral shaft stress injury
- Image beyond the hip when clinically indicated
- Adopt a holistic approach, including biomechanical, training, and metabolic assessment
