Difference Between Hip and Pelvis X-ray
A hip X-ray focuses specifically on the hip joint (femoral head and acetabulum), while a pelvis X-ray provides a broader view of the entire pelvic ring, including both hip joints, the sacrum, and pubic bones. 1
Anatomical Coverage
Hip X-ray
- Focuses on a single hip joint
- Shows the femoral head, femoral neck, and acetabulum
- Typically includes:
- Anteroposterior (AP) view with 15 degrees internal rotation
- Cross-table lateral view of the symptomatic hip
- May include specialized views like Dunn view for femoroacetabular impingement 1
Pelvis X-ray
- Shows the entire pelvic ring
- Includes both hip joints, sacrum, iliac wings, and pubic bones
- Typically consists of:
- Anteroposterior (AP) view of the entire pelvis
- Allows comparison between both hip joints 1
Clinical Indications
Hip X-ray
- Evaluation of unilateral hip pain
- Assessment of:
- Osteoarthritis of a single hip
- Suspected labral tears
- Femoroacetabular impingement
- Focal hip pathology 1
Pelvis X-ray
- Evaluation of bilateral hip pain
- Assessment of:
- Pelvic fractures (including sacrum and pubic rami)
- Comparison of both hips for asymmetry
- Pelvic alignment issues
- Sacroiliac joint pathology 1
Standard Approach in Clinical Practice
Most institutions use a combined approach for comprehensive evaluation:
- AP view of the pelvis (showing both hips for comparison)
- Cross-table lateral view of the symptomatic hip
- Some institutions add a separate AP view of the symptomatic hip 1
Technical Considerations
Positioning impacts measurements:
- Minor degrees of hip flexion, abduction, or adduction can significantly affect the measured joint space width
- Hip adduction and 30° flexion can cause apparent widening of joint space
- Hip abduction can cause apparent narrowing of joint space 2
Standardization is crucial:
When to Use Each Type
- Initial evaluation of hip pain: Start with radiographs of the pelvis and hip 1
- Suspected fracture: AP pelvis with cross-table lateral of the symptomatic hip 1
- Chronic hip pain: Begin with pelvis and hip radiographs before considering advanced imaging 1, 4
- Negative radiographs but persistent symptoms: Progress to MRI without contrast 5
Common Pitfalls to Avoid
- Failing to obtain both pelvis and hip views when evaluating hip pain
- Not using standardized positioning techniques
- Overlooking pelvic fractures when focusing only on the hip joint
- Misinterpreting apparent joint space changes due to positioning variations 2
- Ordering advanced imaging before appropriate radiographs have been obtained 5
In summary, while a hip X-ray provides detailed visualization of a single hip joint, a pelvis X-ray offers a broader perspective that includes both hips and the entire pelvic ring. For comprehensive evaluation, both views are typically recommended as the initial imaging approach for hip pain.