What is the most likely diagnosis for a 35‑year‑old aerobic dance instructor who has anterior thigh pain, painful limitation of hip internal rotation, weight‑bearing pain, limp, and pain when hopping, without tenderness or muscle weakness?

Femoral Neck Stress Fracture

This presentation is most consistent with a femoral neck stress fracture. The combination of anterior thigh pain in a high-impact athlete (aerobic dance instructor), progressive weight-bearing pain, painful limitation of hip internal rotation, pain with hopping, and absence of muscle weakness or focal tenderness creates a classic pattern for this diagnosis 1, 2, 3.

Why Femoral Neck Stress Fracture is the Diagnosis

Clinical Pattern Matches Perfectly

• Anterior thigh/groin pain is the most common presenting symptom of femoral neck stress fractures, reported in the majority of cases 2, 4, 3
• Progressive pain with weight-bearing that initially occurs only after prolonged activity but advances to pain with any weight-bearing is pathognomonic for stress fractures 2, 4, 5
• Painful limitation of hip internal rotation is a cardinal finding in femoral neck stress fractures, distinguishing them from soft-tissue injuries 4, 3
• Pain with hopping on the affected leg is a highly specific provocative test for femoral neck stress fractures 3
• Absence of focal bone tenderness is typical early in the course, as stress fractures may not produce point tenderness until more advanced 2, 4

High-Risk Population

• Aerobic dance instructors perform repetitive high-impact loading similar to distance runners and military recruits, the two populations with highest femoral neck stress fracture rates 4, 3
• Femoral neck stress fractures account for 3-5% of all athletic stress fractures and must be considered in any athlete with exercise-related hip/groin pain 4, 3

Why the Other Diagnoses Don't Fit

Greater Trochanteric Pain Syndrome (Option 1)

• Would produce lateral hip pain, not anterior thigh pain 1
• Would have focal tenderness over the greater trochanter on palpation, which this patient lacks 1
• Would not cause painful limitation of internal rotation 1

Piriformis Syndrome (Option 2)

• Produces buttock and posterior thigh pain, not anterior thigh pain 1
• Would have pain with resisted external rotation and abduction, not internal rotation limitation 1
• Typically includes sciatic nerve symptoms (numbness, tingling), which are absent here 1

Torn External Oblique/Inguinal Nerve Entrapment (Option 3)

• Would produce focal tenderness over the inguinal region, which is absent 1
• Would not cause painful limitation of hip internal rotation 1
• Pain pattern would be more superficial and localized to the groin crease 1

Osteitis Pubis (Option 4)

• Produces medial groin pain localized to the pubic symphysis 1
• Would have focal tenderness over the pubic symphysis on palpation, which is absent 1
• Would not cause painful limitation of hip internal rotation 1

Critical Next Steps

Immediate Imaging is Mandatory

Plain radiographs (AP pelvis and lateral femoral head-neck views) must be obtained immediately 6, 1. However, recognize that initial radiographs may be normal for 2+ weeks after symptom onset 4, 3.

If radiographs are negative but clinical suspicion remains high (as in this case), MRI must be performed urgently 2, 7, 3. MRI can detect bone marrow edema and early stress reaction before cortical disruption appears on plain films 2, 7.

Weight-Bearing Must Stop Immediately

This patient must be made non-weight-bearing immediately 2, 4, 5. Continued weight-bearing on an undiagnosed femoral neck stress fracture risks:

• Fracture displacement 4, 5, 3
• Avascular necrosis of the femoral head 2, 4, 5
• Non-union requiring surgical fixation 4, 5

Classification Determines Treatment

Once imaging confirms the diagnosis, treatment depends on fracture location 4, 5, 3:

• Compression-side (inferomedial) fractures: Conservative management with 6-8 weeks non-weight-bearing, followed by gradual return to activity 4, 5, 3
• Tension-side (superolateral) fractures: Require immediate surgical fixation due to high risk of displacement and avascular necrosis 4, 5, 3
• Any displaced fracture: Requires emergency surgical stabilization 4, 5, 3

Critical Pitfalls to Avoid

Delayed diagnosis is the most common error and dramatically worsens outcomes 2, 4, 3. The insidious presentation and initially normal radiographs lead to misdiagnosis as muscle strain or hip impingement 2, 3.

Never rely on radiographs alone when clinical suspicion is high—bone scintigraphy or MRI may be positive 2+ weeks before plain film changes appear 4, 3.

The absence of focal bone tenderness does not exclude stress fracture 2, 4. This patient's lack of tenderness is typical for early-stage femoral neck stress fractures 4.

Painful limitation of hip internal rotation in an athlete with progressive weight-bearing pain should trigger immediate stress fracture evaluation 1, 4, 3. This combination has high specificity for femoral neck involvement 3.