What is the approach to evaluating hip pain?

Evaluation of Hip Pain

The evaluation of hip pain should begin with screening for red flag conditions, followed by plain radiographs as the first imaging test for any concerning hip pain, with MRI indicated when radiographs are negative but clinical suspicion remains high. 1

Initial Assessment: Red Flags and Anatomic Localization

Red Flag Screening

• Immediately evaluate for:
  • Fever (infection)
  • Severe pain or inability to bear weight (fracture)
  • Night pain or unexplained weight loss (tumor)
  • Erythema or warmth (infection)
  • Pain unrelated to activity 1

Anatomic Localization

• Determine pain location to guide diagnosis:
  • Anterior hip/groin: Suggests intra-articular pathology (osteoarthritis, labral tears) 2
  • Posterior hip/buttock: Consider piriformis syndrome, sacroiliac joint dysfunction, lumbar radiculopathy 2
  • Lateral hip: Typically indicates greater trochanteric pain syndrome 2

Physical Examination

Key Maneuvers

• FADIR test (Flexion, Adduction, Internal Rotation): A negative test helps rule out hip disease 3
• Assess range of motion, deformity, and neurovascular status 1
• Evaluate for referred pain from spine or pelvis 3

Diagnostic Imaging Algorithm

Step 1: Plain Radiographs

• Always start with radiographs: AP pelvis and lateral femoral head-neck views 3
• Look for:
  • Osteoarthritis changes (joint space narrowing, osteophytes)
  • Fractures
  • Dysplasia
  • Femoroacetabular impingement (FAI) morphology 1

Step 2: Advanced Imaging (if radiographs negative/equivocal)

• MRI without contrast: For suspected occult fractures, soft tissue injuries, osteonecrosis, tendinopathy, labral tears (sensitivity 99-100%) 1
• MR arthrography: Superior for labral tears and FAI 1
• Ultrasound: For extra-articular soft tissue abnormalities (tendinitis, bursitis) 3, 1
• CT scan: When 3D morphological assessment is needed 3

Diagnostic Categories After Imaging

Hip-related pain can be categorized into three main conditions:

1. Femoroacetabular impingement (FAI) syndrome
2. Acetabular dysplasia and/or hip instability
3. Other conditions (soft tissue pathologies without specific bony morphology) 3

Common Pitfalls to Avoid

• Relying solely on negative radiographs when clinical suspicion remains high can lead to delayed diagnosis and increased complications 1
• Attributing imaging findings to symptoms without clinical correlation: Incidental intra-articular findings are common in asymptomatic individuals 3
• Failing to consider referred pain: Hip pain may originate from the lumbar spine, sacroiliac joint, or other sources 3, 2
• Missing red flags: Delays in diagnosis of serious conditions like infections or tumors can increase morbidity and mortality 1

Special Considerations

• Diagnostic injections: Intra-articular anesthetic injections can provide diagnostic information by distinguishing the source of pain 3
• Aspiration: Consider joint aspiration under ultrasound guidance if infection is suspected 1
• Prosthetic hips: Evaluate for component loosening, periprosthetic osteolysis, liner wear, and fractures 1

Remember that imaging should always be combined with the patient's symptoms and clinical signs and should not be used in isolation 3. The diagnostic approach should be systematic, moving from less to more invasive testing while maintaining high vigilance for serious pathology that could affect morbidity and mortality.