What is the most likely diagnosis for a patient with radiating pain down the anterior lateral thigh into the lower leg, limited lumbar flexion, and inadequate response to ibuprofen (nonsteroidal anti-inflammatory drug)?

Most Likely Diagnosis: L4 Lumbar Radiculopathy

This patient's presentation is most consistent with L4 lumbar radiculopathy, characterized by pain radiating down the anterior lateral thigh into the lower leg, limited lumbar flexion, and negative hip pathology tests.

Clinical Reasoning

Pain Distribution Pattern

• The anterior lateral thigh and lower leg pain distribution follows the L4 dermatome, which is the classic pattern for L4 nerve root involvement 1, 2
• L4 radiculopathy typically presents with pain radiating to the anterior thigh and medial lower leg, distinguishing it from L5 (lateral leg and dorsum of foot) or S1 (posterior leg and lateral foot) distributions 3
• Over 90% of symptomatic lumbar disc herniations occur at L4/L5 and L5/S1 levels, making L4 nerve root compression anatomically plausible 1, 2

Examination Findings Support Radiculopathy

• Limited lumbar flexion by pain indicates spinal pathology rather than isolated hip or peripheral nerve problems 1
• Negative FABER and FADIR tests effectively rule out hip joint pathology (greater trochanteric pain syndrome would show positive hip provocation tests) 1
• Negative straight leg raise does not exclude radiculopathy—the SLR test has only 91% sensitivity, meaning it misses 9% of true cases, and its sensitivity decreases significantly with age 4
• The combination of radicular pain pattern with limited spinal motion establishes the diagnosis even without positive SLR 4

Why Other Diagnoses Are Less Likely

Greater Trochanteric Pain Syndrome - Excluded

• Would present with lateral hip pain localized to the greater trochanter without radiation below the knee 1
• Hip provocation tests (FABER/FADIR) would typically be positive
• Limited lumbar flexion would not be expected

Meralgia Paresthetica - Excluded

• Affects only the lateral femoral cutaneous nerve, causing isolated lateral thigh numbness/burning 1
• Does not cause pain radiating into the lower leg below the knee 1
• Would not cause limited lumbar flexion
• The patient's lack of belt wearing makes nerve compression at the inguinal ligament unlikely

Piriformis Syndrome - Excluded

• Would present with buttock pain radiating down the posterior thigh (sciatic nerve distribution, typically S1) 2
• Pain pattern described is anterior/lateral, not posterior 5
• Would not typically limit lumbar flexion

L5 Radiculopathy - Less Likely

• L5 typically causes lateral leg pain radiating to the dorsum of the foot, not anterior thigh 1, 3
• L5 presents with great toe and foot dorsiflexion weakness, which was not mentioned 1

Management Approach

Initial Conservative Management

• The natural history of lumbar disc herniation with radiculopathy shows improvement within the first 4 weeks with noninvasive management in most patients 1
• Continue activity as tolerated—remaining active is more effective than bed rest 1
• Optimize NSAID dosing (current ibuprofen 600mg twice daily may be subtherapeutic; consider 600-800mg three times daily) 1

Imaging Indications

• Do not obtain immediate imaging unless severe or progressive neurological deficits develop 1
• MRI is indicated only if symptoms persist beyond 4-6 weeks despite conservative management and the patient is a candidate for epidural steroid injection or surgery 1, 4
• The American College of Physicians recommends delaying imaging while offering standard treatments and reevaluating within 1 month for patients without progressive deficits 1

Red Flags Requiring Urgent Evaluation

• Progressive motor weakness (particularly knee extension weakness for L4) 1, 2
• Bladder or bowel dysfunction 2
• Saddle anesthesia suggesting cauda equina syndrome 2

Follow-up Timeline

• Reassess in 1 month if symptoms persist without improvement 1
• Earlier reevaluation warranted if neurological deficits develop or pain becomes severe and refractory 1