Radiographic Imaging for Hip Pain Radiating Down the Leg

Initial Imaging Approach

• The American College of Radiology recommends plain radiographs of both the pelvis and hip as the first imaging test for patients with hip pain radiating down the leg 1, 2, 3
• A complete radiographic evaluation should include anteroposterior (AP) view of the pelvis and frog-leg lateral view of the symptomatic hip 1, 2
• Radiographs serve as an excellent screening tool to identify common disorders such as arthritis, fractures, and bone tumors 1, 2

Secondary Imaging Based on Initial Radiograph Results

• For suspected soft tissue abnormality, the American College of Radiology recommends MRI hip without IV contrast as the first choice, or ultrasound as a valuable alternative 1, 2, 4, 5
• For suspected nerve compression or radiating pain, MRI of the hip without IV contrast is recommended, and consider lumbar spine imaging if clinical suspicion of referred pain from spine pathology 1, 2, 3
• For suspected labral tear or femoroacetabular impingement, MR arthrography is the preferred method, or CT arthrography as an acceptable alternative 2, 5

Special Considerations

• When both hip and spine pathology are suspected, MRI of the hip without IV contrast should be performed to exclude hip pathology 3
• Diagnostic injections can help determine if pain is originating from the hip joint or surrounding structures 1, 3

Common Pitfalls to Avoid

• Failing to obtain both pelvis and hip views may miss important pathology 1, 2
• Proceeding directly to advanced imaging without first obtaining plain radiographs is not recommended 1, 2, 3

Algorithm for Imaging Selection

• If radiographs are negative or equivocal, consider MRI without contrast or ultrasound for suspected soft tissue pathology, MR arthrography for suspected labral tear/impingement, or additional lumbar spine imaging for suspected referred pain 2, 3
• Consider diagnostic injections to confirm the pain source when diagnosis remains unclear after imaging 1, 2, 3

Diagnostic Approach for Hip Pain

Appropriate Diagnostic Methods

• The American College of Radiology recommends MRI hip without IV contrast as the next step for patients with negative, equivocal, or nondiagnostic radiographs, with a rating of 9/9 (usually appropriate) 6, 7
• Image-guided anesthetic and corticosteroid injection into the hip joint itself is rated as appropriate (8/9) by the American College of Radiology for determining if pain is originating from the hip joint when there is concurrent low back, pelvic, or knee pathology 8
• Intra-articular hip injections can provide both diagnostic information and therapeutic benefit when performed under imaging guidance 9

Diagnostic Injection Guidance

• Peripheral nerve blocks of the obturator nerve for chronic pain are specifically listed as experimental/investigational due to insufficient evidence 7

Clinical Decision Algorithm

• For diagnostic confirmation of hip joint as the pain source, use image-guided intra-articular hip injection rather than peripheral nerve blocks 9, 8
• For suspected labral tears or femoroacetabular impingement, MR arthrography is preferred 7

Important Considerations for Post-Surgery Patients

• Post-arthroplasty pain requires specific evaluation protocols that may include infection workup, component positioning assessment, and other specialized tests 6

Management of Ongoing Left Hip Pain with Numbness and Normal X-rays

Diagnostic Imaging

• The American College of Radiology recommends MRI of the hip without IV contrast as the next appropriate imaging study for ongoing hip pain with numbness when radiographs are negative, with a rating of 9/9 for appropriateness 10, 11, 12
• MRI hip without IV contrast is highly sensitive and specific for detecting soft tissue abnormalities, including tendonitis, bursitis, muscle/tendon tears, and nerve compression that could explain the numbness 11
• MRI can detect occult fractures not visible on plain radiographs, particularly stress fractures or basicervical femoral neck fractures, with the American Academy of Orthopaedic Surgeons highlighting the importance of MRI for diagnosis 13
• The American College of Radiology suggests that MRI can evaluate labral tears, though MR arthrography is superior if this is specifically suspected 11, 14
• Image-guided anesthetic injection into the hip joint can be performed concurrently with MRI to determine if pain originates from the hip joint itself versus surrounding structures or referred sources, with a rating of 8/9 for appropriateness 12

Alternative Imaging Considerations

• Ultrasound can be used as an adjunct for evaluating specific soft tissue structures like trochanteric bursitis or iliopsoas tendinopathy, and for guiding diagnostic/therapeutic injections 11, 14
• However, ultrasound is inferior to MRI for comprehensive evaluation of intra-articular pathology and occult fractures 11

What NOT to Do

• The American College of Radiology states that nuclear medicine bone scan, PET imaging, and CT without contrast are NOT appropriate for this clinical scenario, with ratings of 1/9 for appropriateness 10, 14
• These modalities do not adequately evaluate soft tissue pathology causing numbness, expose patients to unnecessary radiation, and provide less diagnostic information than MRI 10, 11, 12, 14

Critical Pitfalls to Avoid

• The American Academy of Orthopaedic Surgeons highlights that occult femoral neck fractures can present with normal initial radiographs, requiring MRI for diagnosis 13
• Delaying MRI if pain worsens or persists beyond 2-3 days may indicate an occult fracture requiring urgent surgical intervention 13
• Proceeding directly to MR arthrography is not recommended unless there is specific clinical suspicion for labral tear or femoroacetabular impingement 11, 14

Imaging Guidance and Recommendations for Chronic Hip Pain Evaluation

Image‑Guided Diagnostic Injections

• The American College of Radiology states that intra‑articular hip injections can be performed safely under either ultrasound or fluoroscopic guidance to both confirm the hip joint as the pain source and provide therapeutic benefit in osteoarthritis patients. 15

Advanced Imaging Techniques to Avoid

• According to the American College of Radiology, magnetic resonance arthrography should not be used for routine evaluation of chronic hip pain in elderly patients unless there is a specific clinical suspicion for a labral tear or femoroacetabular impingement, which is uncommon in this population. 15

Limited Role of Nuclear Medicine

• The American College of Radiology advises that nuclear medicine studies (e.g., bone scans, PET) are not useful for assessing chronic hip pain in the described clinical scenario and should be avoided. 15