What is the cause of hip pain in a mid-50s adult with normal and symmetric hip joints bilaterally, no evidence of joint effusion, arthritic changes, or soft tissue abnormalities on imaging, and no significant past medical history?

Hip Pain with Normal Imaging in Mid-50s Adult

In a mid-50s adult with hip pain and completely normal radiographic imaging, the most likely diagnosis is L3 radiculopathy, which should be evaluated with lumbar spine MRI, as this condition characteristically presents with hip/lateral thigh pain but normal hip imaging and is distinguished by dermatomal sensory changes along the medial lower leg. 1, 2

Diagnostic Approach

First-Line Consideration: Referred Pain from Lumbar Spine

When hip imaging is entirely normal in a patient with hip pain, lumbar spine pathology, particularly L3 radiculopathy, must be the primary consideration 1, 2. The L3 nerve root distribution includes buttock, lateral hip, and anterior-lateral thigh pain—areas commonly misattributed to hip pathology 1, 2.

Key distinguishing features to assess:

• Dermatomal sensory loss along the medial aspect of the lower leg is pathognomonic for L3 nerve root involvement and definitively excludes primary hip pathology 1, 2
• Negative hip-specific tests (FABER and FADIR) effectively exclude intra-articular hip pathology 1, 2
• The straight leg raise test may be negative in upper lumbar radiculopathy (L3-L4), so its absence does not exclude this diagnosis 1, 2

Second-Line Consideration: Occult Soft Tissue or Early Intra-articular Pathology

If lumbar spine evaluation is negative, MRI of the hip without contrast should be obtained as the next step 3. The ACR Appropriateness Criteria strongly recommend MRI as the first advanced imaging after negative radiographs for chronic hip pain 3.

MRI is superior for detecting:

• Extra-articular soft tissue abnormalities including iliopsoas bursitis, trochanteric bursitis, abductor tendinosis or tears, hamstring injuries, and athletic pubalgia 3
• Early labral tears without associated bony morphology changes 3
• Occult chondral lesions and ligamentum teres pathology 3
• Early avascular necrosis before radiographic changes appear 4

Third-Line Consideration: Hip Joint Effusion

Ultrasound of the hip can detect joint effusion as small as 1 mL, which may be present despite normal radiographs 3, 5. Research demonstrates that 38% of adults with hip pain have ultrasonic evidence of joint effusion despite normal clinical examination 5.

Clinical correlates of occult effusion include:

• Pain in the groin or medial thigh 5
• Pain aggravated by lying on the affected side 5
• Nocturnal pain has 85% sensitivity and 94% specificity for hip joint effusion 6
• Decreased range of motion in extension, internal rotation, abduction, or flexion 5
• Painful external rotation and tenderness on palpation in the groin 5

Recommended Diagnostic Algorithm

Step 1: Detailed neurological examination

• Assess for dermatomal sensory loss along medial lower leg (L3 distribution) 1, 2
• Check for asymmetric deep tendon reflexes 2
• Perform hip-specific tests (FABER, FADIR) to exclude intra-articular pathology 1, 2

Step 2: If neurological findings suggest radiculopathy

• Obtain lumbar spine MRI without contrast to evaluate for disc herniation or foraminal stenosis at L3 level 1, 2
• Plain radiographs of lumbar spine may be obtained first if structural concerns exist, but MRI provides superior nerve root visualization 1, 2

Step 3: If lumbar spine evaluation is negative

• Obtain hip MRI without contrast to evaluate soft tissue structures, labrum, cartilage, and bone marrow 3
• Consider hip ultrasound if clinical signs suggest effusion (nocturnal pain, groin tenderness, restricted motion) 5, 6

Step 4: If imaging remains unrevealing

• Consider diagnostic/therapeutic injection under image guidance to localize pain source 3
• Evaluate for referred pain from other sources (knee, spine) 3

Critical Pitfalls to Avoid

Do not assume hip pain originates from the hip joint when imaging is normal—referred pain from L3 radiculopathy is a common mimic 1, 2. The International Hip-related Pain Research Network emphasizes that imaging must always be combined with patient symptoms and clinical signs, as diagnostic imaging in isolation has limited utility 3.

Do not overlook occult effusion—ultrasound can reveal joint effusion in clinically and radiologically normal-appearing hips, particularly in patients with nocturnal pain 7, 6.

Do not delay MRI if conservative management fails—early detection of soft tissue pathology, labral tears, or early avascular necrosis significantly impacts treatment decisions and outcomes 3.

Treatment Based on Diagnosis

For confirmed L3 radiculopathy:

• Activity modification and physical therapy 1
• NSAIDs for pain control 1
• Monitor for 6-12 weeks unless red flags present 1
• Consider epidural steroid injection at L3 level under fluoroscopic guidance if conservative management fails 1, 2
• Neurosurgical referral if progressive neurologic deficit or failure of conservative management after 6-12 weeks 1, 2

For soft tissue pathology identified on MRI:

• Targeted physical therapy based on specific diagnosis 3
• Image-guided diagnostic/therapeutic injections (trochanteric, iliopsoas bursa) 3