Hip pain is a common complaint across various age groups, and its etiology can range from simple musculoskeletal strain to more complex conditions such as hip fractures, infections, or systemic diseases.

While an X-ray is often the first imaging modality used to assess hip pain, it is not uncommon for patients to present with persistent or significant hip pain despite a normal X-ray. This scenario can be perplexing for both the patient and the healthcare provider, necessitating a deeper investigation into the potential causes.

This article explores the various causes of hip pain with a normal X-ray, possible treatment approaches, and critical red flags that should alert clinicians to more serious underlying conditions.

Causes of hip pain with a normal X-ray

1. Soft Tissue Injuries and Tendinopathies

The hip is surrounded by numerous muscles, tendons, and ligaments, all of which are potential sources of pain. Tendinopathies, particularly of the hip flexors, gluteus medius, and iliotibial (IT) band, are common causes of hip pain not visible on an X-ray. Tendinitis, bursitis, or even partial tears can cause considerable discomfort but may not show up on standard imaging.

• Hip Flexor Tendinitis: Inflammation of the iliopsoas muscle can result from overuse, particularly in athletes or individuals engaging in repetitive activities like running or cycling.
• Gluteus Medius Tendinitis: This condition, often referred to as ‘rotator cuff tear of the hip,’ can cause pain on the lateral aspect of the hip, particularly with weight-bearing activities.
• Trochanteric Bursitis: The bursa overlying the greater trochanter can become inflamed, leading to lateral hip pain, often exacerbated by lying on the affected side or prolonged standing.

2. Labral Tears and Hip Impingement

Hip labral tears, often associated with femoroacetabular impingement (FAI), can result in significant pain and functional impairment. The labrum is a cartilaginous structure that lines the acetabulum and helps stabilize the hip joint. Tears in this structure can occur due to trauma, repetitive motion, or congenital abnormalities.

• Femoroacetabular Impingement (FAI): This condition arises from abnormal contact between the femoral head and the acetabulum, leading to labral damage and cartilage degeneration. While an X-ray might reveal bony abnormalities in severe cases, early-stage FAI and labral tears often require advanced imaging like magnetic resonance imaging (MRI) or magnetic resonance arthrography (MRA) for diagnosis.

3. Hip Osteoarthritis (Early Stage)

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage loss, joint space narrowing, and osteophyte formation. In the early stages, patients may present with hip pain despite normal X-rays, as structural changes may not be visible yet. Symptoms include stiffness, particularly in the morning, and pain that worsens with activity. Eventually, as the disease progresses, radiographic changes such as joint space narrowing and osteophyte formation will become apparent.

4. Referred Pain from the Spine or Pelvis

The hip region can be affected by pain referred from nearby structures, particularly the lumbar spine and the sacroiliac joint. Conditions like lumbar disc herniation, spinal stenosis, or sacroiliitis can cause pain that radiates to the hip, often mimicking primary hip pathology. Patients with lumbar spine involvement often report pain radiating down the leg or exacerbation of pain with certain spinal movements, such as forward flexion or extension.

5. Avascular Necrosis (AVN) of the Hip

Avascular necrosis (AVN) occurs when the blood supply to the femoral head is compromised, leading to the death of bone tissue. In the early stages of AVN, X-rays can appear normal, but the condition can progress rapidly if untreated, eventually leading to the collapse of the femoral head and severe arthritis. Risk factors for AVN include corticosteroid use, alcohol abuse, trauma, and certain medical conditions such as sickle cell disease and lupus. MRI is the gold standard for detecting AVN in its early stages.

6. Snapping Hip Syndrome (Coxa Saltans)

Snapping hip syndrome, or coxa saltans, occurs when a tendon or muscle slides over a bony prominence in the hip, creating a snapping sensation or sound. While generally benign, it can be painful and may interfere with daily activities. This condition can be classified into external (involving the IT band snapping over the greater trochanter), internal (involving the iliopsoas tendon snapping over structures near the hip joint), or intra-articular (involving labral tears or loose bodies in the hip joint).

7. Transient Osteoporosis of the Hip (TOH)

Transient osteoporosis is a rare, self-limiting condition that causes sudden-onset hip pain, often in young to middle-aged men or pregnant women. It is characterized by temporary bone demineralisation, usually of the femoral head, which may not be apparent on X-ray in the early stages. MRI can help confirm the diagnosis by revealing bone marrow oedema.

8. Greater Trochanteric Pain Syndrome (GTPS)

Greater trochanteric pain syndrome encompasses a variety of conditions that cause pain over the lateral aspect of the hip, including trochanteric bursitis, tendinopathy, and gluteal muscle tears. GTPS is a common cause of chronic hip pain, particularly in middle-aged women. Diagnosis is typically clinical, as X-rays are often normal, but MRI or ultrasound may reveal soft tissue abnormalities.

9. Stress Fractures

Stress fractures, particularly in the femoral neck, can cause significant hip pain and may not always be visible on initial X-rays. These fractures are more common in athletes, military recruits, and individuals with osteoporosis. An MRI or bone scan is often necessary for early diagnosis.

Help with managing hip pain

Hip pain with a normal X-ray can be challenging to diagnose and manage due to the wide range of potential causes, from benign soft tissue injuries to more serious conditions like avascular necrosis or malignancy.

A thorough clinical evaluation, combined with the appropriate use of advanced imaging modalities like MRI or CT scans, is crucial in identifying the underlying cause and directing appropriate treatment. Red flags such as night pain, systemic symptoms, or a history of trauma should prompt further investigation to rule out serious underlying pathology. Through a careful, systematic approach, clinicians can effectively manage hip pain, providing relief and preventing complications.

If you are experiencing hip pain and would like a consultation with a hip joint replacement specialist to discuss treatment options, get in touch to schedule an appointment with Mr Sulaiman Alazzawi.