What is the diagnosis and treatment for a patient with inner thigh pain that worsens when lying down and everting the leg, considering potential causes such as hip adductor strain, groin pathology, or nerve entrapment?

Inner Thigh Pain: Diagnosis and Management

For inner thigh pain worsening with lying down and leg eversion, the primary differential diagnosis is adductor-related groin pain (most commonly adductor longus tendinopathy), which must be distinguished from hip-related pain, obturator nerve entrapment, and referred pain from lumbar spine pathology. 1, 2

Diagnostic Approach

Clinical Examination Priorities

The key distinguishing feature is that adductor-related groin pain localizes to the inner thigh/groin region and worsens with resisted hip adduction, while hip-related pain typically presents with anterior hip/groin pain that is positive on the FADIR (flexion-adduction-internal rotation) test. 1, 2

• A negative FADIR test helps rule out intra-articular hip disease, making adductor pathology or nerve entrapment more likely 1
• Pain with resisted hip adduction and palpable tenderness over the adductor longus origin at the pubic tubercle suggests adductor tendinopathy 3, 4
• Dermatomal sensory loss along the medial lower leg indicates L3 radiculopathy rather than musculotendinous pathology 5
• Obturator nerve entrapment presents with medial thigh pain and sensory changes in the medial thigh distribution 6

Critical Exclusions

Both non-musculoskeletal and serious pathological conditions (tumors, infections, stress fractures) as well as competing musculoskeletal conditions (lumbar spine pathology) must be excluded before diagnosing adductor-related or hip-related pain. 1

Imaging Algorithm

Initial Imaging

Plain radiographs (AP pelvis and frog-leg lateral hip views) should be obtained first to exclude fractures, arthritis, and bone tumors. 7, 8

Advanced Imaging Based on Clinical Suspicion

If radiographs are negative and adductor tendinopathy is suspected, MRI hip without IV contrast is the next appropriate study (rated 9/9 by the American College of Radiology), as it can detect intratendinous tears of the adductor longus—the most specific sign of tendinopathy. 7, 3

• Ultrasound is a valuable alternative for evaluating adductor tendons and can guide diagnostic/therapeutic injections 7, 3
• If nerve entrapment is suspected (numbness, dermatomal sensory loss), MRI without contrast is essential to evaluate for nerve compression 7, 5
• If lumbar radiculopathy is suspected based on dermatomal patterns, lumbar spine MRI without contrast should be obtained 5

Common Imaging Pitfalls

• Asymptomatic findings (tendinosis, calcifications, cortical erosions) are common in athletes on imaging and should not be interpreted as the pain source without correlating clinical findings 3
• Failing to obtain both pelvis and hip views may miss important pathology 7
• Nuclear medicine bone scan, PET imaging, and CT without contrast are NOT appropriate for this clinical scenario 7

Differential Diagnosis Framework

Adductor-Related Groin Pain

• Adductor longus tendinopathy is the main cause of adductor-related groin pain and leads to significant reduction in activity 3
• Pain localizes to the inner thigh/groin, worsens with resisted adduction and stretching 3, 4
• Intratendinous tear on MRI or ultrasound is the most specific diagnostic finding 3

Hip-Related Pain (Less Likely with Inner Thigh Location)

• Hip-related pain typically presents as anterior hip/groin pain, though it may radiate to the back, buttock, or thigh 1
• The three main categories are: (1) FAI syndrome, (2) acetabular dysplasia/hip instability, and (3) other conditions (labral, chondral, ligamentum teres pathology) 1
• Hip-related pain can coexist with other types of groin pain, making diagnosis challenging 1

Nerve Entrapment

• Obturator nerve entrapment causes medial thigh pain and sensory changes 6
• L3 radiculopathy presents with dermatomal sensory loss along the medial lower leg, distinguishing it from hip pathology 5
• Peripheral nerve blocks of the obturator nerve are considered experimental/investigational due to insufficient evidence 7

Treatment Algorithm

Conservative Management (First-Line)

• Activity modification and physical therapy for 6-12 weeks 5
• NSAIDs for pain control 5
• Manual therapy, stretching and strengthening exercises for nerve entrapment cases 6

Diagnostic and Therapeutic Injections

Image-guided anesthetic and corticosteroid injection can provide both diagnostic confirmation and therapeutic benefit when the pain source remains unclear after imaging. 7

• For adductor tendinopathy, ultrasound-guided injection into the affected tendon can be both diagnostic and therapeutic 7, 3
• For suspected hip joint pathology, intra-articular hip injection under imaging guidance (rated 8/9 by ACR) can determine if pain originates from the hip joint versus surrounding structures 7

Surgical Referral Indications

• Progressive neurologic deficit requires urgent neurosurgical or spine surgery referral 5
• Failure of conservative management after 6-12 weeks 5
• Adductor longus tendinopathy requiring surgical management when conservative treatment fails 3
• Neurolysis or neurectomy for nerve entrapment when conservative treatment is ineffective 6

Critical Clinical Pitfall

The specific symptom of pain worsening when lying down and everting the leg is unusual for typical adductor strain (which worsens with adduction, not eversion) and should raise suspicion for either nerve entrapment or referred pain from the lumbar spine or hip joint. 5, 6, 2 This atypical presentation mandates comprehensive imaging with MRI to exclude occult pathology.