Diagnostic Approach to Unilateral Hip Pain

Initial Evaluation

The American College of Radiology recommends starting with plain radiographs (AP pelvis and lateral femoral head-neck views) as the first imaging test in nearly all cases of unilateral hip pain, combined with a targeted history and physical examination to localize pain and guide subsequent testing 1, 2
Night pain suggests tumor or advanced osteonecrosis, and mechanical symptoms such as locking or snapping suggest labral pathology or snapping hip syndrome 3
The FADIR test (Flexion-Adduction-Internal Rotation) can help rule out hip-related pain in young and middle-aged adults, though sensitivity is limited 4, 5

Plain radiographs are an excellent screening tool for common disorders such as osteoarthritis, fractures, tumors, dysplasia, and FAI morphology 1, 2
MRI without contrast is the first advanced imaging technique after negative or non-diagnostic radiographs, and is useful for detecting soft tissue pathology, occult fractures, and osteonecrosis 1, 2
MR arthrography or CT arthrography can be used to evaluate specific intra-articular structures such as the labrum, cartilage, and ligamentum teres 4

Intra-articular causes of hip pain include osteoarthritis, labral tears, FAI syndrome, acetabular dysplasia, and chondral defects 1, 2, 4, 6
Extra-articular causes include greater trochanteric pain syndrome, iliopsoas tendinopathy, and hamstring tendinopathy 1, 2
Referred pain from lumbar radiculopathy, sacroiliac joint dysfunction, and knee pathology should also be considered 1

Suspected septic arthritis requires urgent joint aspiration 7
Hemarthrosis requires checking coagulation studies before invasive procedures 7
Inflammatory arthropathy with systemic symptoms requires laboratory tests such as ESR, CRP, ANA, and rheumatoid factor 7