What is the cause and management of a painful inner thigh that worsens when lying down and everting the involved leg?

Painful Inner Thigh When Lying Down and Everting Leg: Cause and Management

The most likely diagnosis is hip adductor strain or groin pathology, though meralgia paresthetica (lateral femoral cutaneous nerve entrapment) should be considered if symptoms include burning/tingling sensations along the anterolateral thigh. 1

Clinical Differentiation

The key to diagnosis lies in the specific characteristics of the pain and associated findings:

Vascular vs. Neurogenic Pain

• Vascular claudication can be excluded if pulses (femoral, dorsalis pedis, posterior tibial) are normal and the pain includes tingling/burning sensations, as these are not characteristic of arterial insufficiency 1
• Peripheral arterial disease typically presents as cramping/aching with walking that is relieved by rest within 10 minutes, with diminished or absent pulses 1
• The absence of both dorsalis pedis and posterior tibial pulses strongly suggests peripheral arterial disease, while the presence of either pulse makes PAD less likely 2

Nerve Entrapment Syndromes

• Meralgia paresthetica presents with pain or dysesthesia in the anterolateral thigh caused by entrapment of the lateral femoral cutaneous nerve at the anterior superior iliac spine 3
• This condition can mimic low-back pain due to similarity of symptoms and should be considered in the differential diagnosis 3
• Pain that does not radiate from the tailbone down to the toes, with preserved motor function and reflexes, helps rule out lumbar radiculopathy 1

Restless Legs Syndrome (RLS)

• RLS causes an urge to move the legs with uncomfortable sensations that begin or worsen during rest (lying or sitting) 4
• Symptoms are partially or totally relieved by movement such as walking or stretching 4
• RLS has a circadian pattern with symptoms worsening in the evening/night and improving toward morning 4
• Critical distinction: RLS must be differentiated from mimics including leg cramps, leg edema, venous stasis, positional discomfort, muscle aches, and arthritis 4

Essential Physical Examination

Perform a systematic examination to exclude alternative diagnoses:

• Pulse examination: Check femoral, popliteal, posterior tibial, and dorsalis pedis pulses bilaterally 1
• Neurologic assessment: Test motor strength in all lower extremity muscle groups, sensory distribution, and deep tendon reflexes 1
• Straight leg raise test: Assess for concurrent lumbar radiculopathy 1
• Leg length discrepancy: Measure for anatomical variations that can cause piriformis syndrome or referred pain 5

Red flag: If true motor weakness is present, obtain urgent lumbar spine MRI to rule out nerve root compression 1

Diagnostic Workup

Initial Testing

• If vascular disease suspected: Obtain ankle-brachial index (ABI) and consider vascular imaging if ABI is abnormal 4
• If nerve entrapment suspected: Nerve conduction studies can confirm diagnosis but are not always necessary if clinical presentation is classic 4
• If inflammatory process suspected: Check ESR and CRP, though these are typically normal in isolated nerve entrapment 6

Advanced Imaging

• Plain radiographs of the hip and pelvis to exclude structural abnormalities 6
• MRI is reserved for cases where diagnosis remains unclear or to assess for soft tissue pathology 7

Management Approach

Conservative Management (First-Line)

For meralgia paresthetica or nerve entrapment:

• Remove precipitating factors: Tight belts, restrictive clothing, or external compression 3
• Bed rest: 15 days followed by avoidance of aggravating factors for 45 days 3
• NSAIDs: Oral administration for pain control 3
• Nerve block: 10 mL of bupivacaine 0.25% can provide immediate pain relief and diagnostic confirmation 3

For Restless Legs Syndrome

• Check serum ferritin: Values less than 50 ng/mL warrant iron supplementation 4
• Medication review: Discontinue or substitute tricyclic antidepressants, SSRIs, lithium, or dopamine antagonists that may exacerbate symptoms 4
• Lifestyle modifications: Address increased BMI, caffeine intake, sedentary lifestyle, and tobacco use 4

Surgical Intervention

• Reserved for refractory cases of nerve entrapment after conservative management fails 8
• Outcomes are better when clear dermatomal pain distribution or focal weakness/sensory symptoms appropriate for the nerve are present 8

Common Pitfalls to Avoid

• Do not assume fibromyalgia or generalized pain syndrome without excluding specific structural or neurologic causes 9
• Do not overlook medication-induced myalgias: Statins are a common cause of lower extremity myalgias 2
• Do not miss coexisting pathologies: Fascial dysfunction may predispose to both compartment syndromes and neurovascular entrapment, and multiple conditions often coexist 8
• Do not delay imaging if motor weakness is present: This requires urgent evaluation for nerve root compression 1