Musculoskeletal Imaging

What Is the Next Imaging Study for Chronic Hip Pain When Radiographs Are Negative?

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What Is the Next Imaging Study for Chronic Hip Pain When Radiographs Are Negative?

A 32-year-old marathon runner presents with several months of insidious, deep anterior hip pain, accompanied by a catching sensation during deep flexion. The pain limits their training and is worst after long runs. You perform a thorough physical exam, noting a positive anterior impingement sign. An initial AP pelvis and lateral hip radiograph series is read as negative for fracture, dislocation, or significant osteoarthritis. You suspect an intra-articular process like femoroacetabular impingement (FAI) or a labral tear. The next step is choosing the right advanced imaging study to confirm the diagnosis and guide treatment. This article details the clinical workflow for this specific scenario, where the American College of Radiology (ACR) rates MR arthrography of the hip as Usually Appropriate.

Who Fits This Clinical Scenario?

This guidance applies to a specific patient population, typically active adults under 50, presenting with chronic, activity-related hip pain suggestive of an intra-articular mechanical cause. The key inclusion criteria are:

  • Symptom Duration: The pain is chronic, not acute from a specific traumatic event.
  • Clinical Suspicion: The history and physical exam point toward femoroacetabular impingement (e.g., groin pain with flexion, adduction, and internal rotation) or acetabular dysplasia. Symptoms often include clicking, catching, or locking.
  • Initial Radiographs: Standard radiographs of the hip and pelvis have been performed and are either entirely negative or nondiagnostic, showing no clear cause for the patient’s symptoms like advanced osteoarthritis, fracture, or avascular necrosis.

It is crucial to distinguish this scenario from others. This workflow is not for:

  • Initial Imaging: Patients with chronic hip pain who have not yet had radiographs. The first step in nearly all cases is a standard radiograph series.
  • Suspected Extra-articular Pain: Patients whose pain is located laterally over the greater trochanter, suggesting a gluteal tendinopathy or trochanteric bursitis. This follows a different diagnostic pathway.
  • Obvious Osteoarthritis on Radiographs: If initial X-rays already show moderate to severe joint space narrowing and osteophytes, the diagnosis is established, and the imaging question shifts to evaluating cartilage integrity or pre-operative planning, which is a separate ACR variant.

What Diagnoses Are You Working Up in This Scenario?

When initial radiographs are unrevealing in a patient with mechanical hip symptoms, the differential diagnosis shifts to soft-tissue and subtle osseous abnormalities that X-rays cannot adequately visualize. Advanced imaging is ordered to investigate these specific possibilities.

Femoroacetabular Impingement (FAI): This is a primary consideration. FAI is a motion-related clinical disorder of the hip with a triad of symptoms, clinical signs and imaging findings. It relates to abnormal contact between the femoral head-neck junction and the acetabular rim. There are two main types: “cam” morphology (an aspherical femoral head) and “pincer” morphology (acetabular overcoverage), which frequently coexist. This repetitive abnormal contact can lead to damage of the labrum and articular cartilage.

Acetabular Labral Tear: The labrum is a fibrocartilaginous ring that lines the acetabular socket, providing stability and a crucial sealing function for joint fluid. Tears are a common source of pain and mechanical symptoms. They are very frequently associated with underlying FAI or hip dysplasia, which are the primary drivers of the injury.

Developmental Dysplasia of the Hip (DDH): This condition involves an abnormally shallow acetabulum, leading to inadequate coverage of the femoral head. This creates instability and concentrates forces over a smaller surface area, predisposing the joint to labral tears and premature chondral damage, eventually leading to early-onset osteoarthritis. Mild, previously undiagnosed dysplasia can present as activity-related hip pain in young adults.

Chondral Injury: Damage to the articular cartilage of the femoral head or acetabulum is another key diagnosis. This can range from softening and fibrillation to full-thickness defects. These injuries are often the direct result of the mechanical conflict in FAI or the instability from dysplasia.

Why Is MR Arthrography the Top Study for Suspected Hip Impingement or Dysplasia?

When radiographs are negative but suspicion for intra-articular pathology remains high, magnetic resonance (MR) imaging is the definitive next step. The ACR designates both MR arthrography hip and MRI hip without IV contrast as Usually Appropriate.

MR arthrography is often considered the most sensitive test for this indication. The procedure involves injecting a dilute gadolinium-based contrast agent directly into the hip joint under fluoroscopic or ultrasound guidance. This distends the joint capsule and forces contrast into any potential clefts or tears. This technique provides exquisite detail of the labrum and articular cartilage surfaces, making it highly effective for detecting subtle labral tears, delamination of cartilage, and other small intra-articular abnormalities that can be missed on a non-arthrographic study.

A non-contrast MRI of the hip is also rated Usually Appropriate and is an excellent, non-invasive alternative. It provides superb visualization of osseous morphology, making it ideal for identifying the cam or pincer lesions characteristic of FAI. It can also detect most labral tears (especially when a joint effusion is present), chondral defects, and bone marrow edema. It is often the preferred next step if a patient is hesitant to undergo a joint injection or if the primary question is related to bony morphology.

Let’s compare these to other options rated lower by the ACR for this specific scenario:

  • CT arthrography hip (May be appropriate): While this study provides excellent detail of the labrum and bone, it has lower intrinsic soft-tissue contrast compared to MRI for evaluating the articular cartilage. Crucially, it involves significant ionizing radiation (☢☢☢ 1-10 mSv), whereas MRI involves none (0 mSv). It is typically reserved for patients with contraindications to MRI.
  • US hip (Usually not appropriate): Ultrasound is valuable for assessing superficial structures, guiding injections, and detecting effusions or synovitis. However, it cannot penetrate deep enough to visualize the entirety of the labrum, the articular cartilage, or the osseous morphology of the femoral head-neck junction, making it inadequate for working up FAI or dysplasia.

Once you’ve decided on an MRI, understanding the specifics of the protocol is key. For a detailed overview of the technique, sequences, and interpretation principles, our protocol guide is a valuable resource: MRI Hip Without Contrast.

What’s Next After an MR Arthrography of the Hip?

The results of the advanced imaging study will guide the subsequent clinical pathway. The goal is to correlate the imaging findings with the patient’s specific symptoms and exam to formulate a treatment plan.

  • Positive for FAI and/or a Labral Tear: If the MR arthrogram confirms a labral tear, significant chondral injury, and/or osseous morphology consistent with FAI that explains the patient’s symptoms, the next step is typically a referral to an orthopedic surgeon. The surgeon will discuss treatment options, which may range from conservative management (physical therapy, activity modification) to surgical intervention, most commonly hip arthroscopy to repair the labrum and correct the underlying bony impingement.
  • Positive for Significant Dysplasia: If the imaging reveals findings of developmental dysplasia of the hip, a referral to an orthopedic surgeon specializing in hip preservation surgery is warranted. Treatment for symptomatic dysplasia in young adults may involve a periacetabular osteotomy (PAO) to reorient the socket and improve femoral head coverage.
  • Negative or Non-diagnostic Study: If the MR arthrogram is negative, it significantly lowers the likelihood of a major intra-articular structural problem. The focus should shift back to a clinical re-evaluation. Consider extra-articular pain generators (e.g., gluteal tendinopathy, athletic pubalgia, lumbar spine referral). An image-guided diagnostic injection of local anesthetic into the hip joint, which is rated May be appropriate, can be a powerful tool. If the patient’s pain is temporarily but significantly relieved, it confirms the hip joint as the source, even with negative advanced imaging.

Pitfalls to Avoid (and When to Get Help)

Navigating the workup for chronic hip pain requires careful attention to detail to avoid common missteps.

  1. Under-reading Radiographs: Subtle signs of FAI, such as a small cam lesion on the femoral neck or a “crossover sign” indicating pincer morphology, can be easily missed on a standard AP view. Ensure appropriate views (e.g., a 45° Dunn view or frog-leg lateral) are obtained and reviewed carefully before concluding the radiographs are truly negative.
  2. Attribution Error: Do not automatically attribute the patient’s pain to an incidental imaging finding. Small labral tears can be asymptomatic. The clinical correlation between the location of the pathology on MRI and the patient’s symptoms on exam is paramount.
  3. Ignoring the “Spine-Hip Syndrome”: Pathology in the lumbar spine, particularly L2-L4 radiculopathy, can refer pain to the anterior hip and groin, closely mimicking intra-articular hip pain. Always maintain a broad differential and consider the spine if the hip workup is negative.

If the clinical picture is confusing, the imaging is equivocal, or the patient fails to improve with initial management, it is appropriate to escalate care by referring to an orthopedic or sports medicine specialist for further evaluation.

Related ACR Topics and Tools

This article focuses on one specific clinical variant. For a comprehensive overview of imaging for all chronic hip pain scenarios, from initial workup to post-operative evaluation, please consult our parent guide. You can also use the tools below to explore other scenarios, protocols, and radiation safety topics.

Frequently Asked Questions

Why is MR arthrography sometimes preferred over non-contrast MRI if both are ‘Usually Appropriate’?

While both are excellent studies, MR arthrography is generally considered more sensitive for detecting subtle or small labral tears and evaluating the integrity of the articular cartilage. The injected contrast distends the joint, forcing fluid into small clefts and providing a sharp outline of the intra-articular structures. This can be particularly helpful when clinical suspicion is high but a non-contrast MRI is equivocal.

What if my patient refuses the intra-articular injection for an MR arthrogram?

A non-contrast MRI of the hip is an excellent alternative and is also rated ‘Usually Appropriate’ by the ACR. It avoids the risks and discomfort of a joint injection while still providing high-quality diagnostic information, especially for assessing the bony morphology of FAI and detecting larger labral or chondral injuries. It is a perfectly acceptable first choice for advanced imaging in this scenario.

Can I just order a CT scan instead of an MRI for suspected impingement?

While CT arthrography is rated as ‘May be appropriate,’ it is generally not the first choice. MRI provides superior soft-tissue contrast for evaluating the labrum and, most importantly, the articular cartilage. CT also exposes the patient to ionizing radiation, which is a key consideration in the typically young patient population presenting with this condition. CT is usually reserved for patients who have a contraindication to MRI.

My patient’s radiographs were read as ‘mild degenerative changes.’ Does this workflow still apply?

It depends on the degree of change and the patient’s age. If the changes are very mild and disproportionate to the patient’s severe mechanical symptoms, an underlying structural issue like FAI or dysplasia may still be the primary driver. However, if the radiographs show definite, albeit mild, osteoarthritis (e.g., early joint space narrowing), the scenario may shift to evaluating articular cartilage integrity, which is a distinct ACR variant with slightly different recommendations.

Is an MRI with intravenous (IV) contrast useful in this scenario?

No, an MRI of the hip with and without standard IV contrast is rated as ‘Usually not appropriate’ for this specific indication. IV contrast is useful for evaluating synovitis, infection, or tumors, but it does not improve visualization of the mechanical structures like the labrum and cartilage in the way that direct intra-articular contrast does. For working up impingement or dysplasia, a non-contrast MRI or an MR arthrogram is the correct choice.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 30, 2026