What is the management approach for a patient with groin pain and ultrasound (USG) findings of edema around the hip joint?

Management of Groin Pain with Ultrasound Findings of Intramuscular and Peri-articular Edema Around the Hip

Obtain plain radiographs (X-ray pelvis and hip) as the mandatory first imaging step, followed by MRI of the hip without IV contrast to characterize the soft tissue edema and identify the underlying cause. 1

Initial Imaging Algorithm

First-Line Imaging

• Plain radiographs are rated 9/9 (usually appropriate) as the initial test for any patient presenting with hip/groin pain, regardless of ultrasound findings 1
• Both X-ray pelvis and X-ray hip are complementary and should be obtained together 1
• Radiographs exclude osseous pathology, arthritis, fractures, and structural abnormalities before proceeding to advanced imaging 1

Second-Line Imaging After Radiographs

• MRI hip without IV contrast is rated 9/9 (usually appropriate) when radiographs are negative or nondiagnostic and extra-articular soft tissue pathology is suspected 1, 2
• MRI provides superior characterization of intramuscular edema, tendinitis, bursitis, muscle tears, and synovitis that ultrasound has detected 1, 2
• The ultrasound findings of edema suggest extra-articular noninfectious soft tissue abnormality, making MRI without contrast the definitive next step 1

Differential Diagnosis to Consider

The edema pattern on ultrasound requires systematic evaluation for:

Tendinopathy and Bursitis

• Iliopsoas tendinitis/bursitis is a common cause of groin pain with peri-articular edema 3, 4
• Trochanteric bursitis presents with lateral hip pain and peri-articular fluid 1
• MRI without contrast is highly sensitive for detecting these conditions 1, 2

Muscle Pathology

• Quadratus femoris muscle edema from ischiofemoral impingement syndrome can cause groin pain and is often overlooked 5
• Adductor or hip flexor muscle strains present with intramuscular edema 1
• MRI identifies muscle tears, strains, and inflammatory myopathies 2

Intra-articular Pathology

• Joint effusion and synovitis can extend to peri-articular tissues 1
• Labral tears may present with secondary inflammatory changes 6
• If intra-articular pathology is suspected after MRI, consider MR arthrography (rated 9/9) for labral evaluation 1

Infection Consideration

• If infection is clinically suspected (fever, elevated inflammatory markers, acute presentation), MRI with IV contrast increases diagnostic confidence 2
• Joint aspiration under ultrasound or fluoroscopic guidance is the gold standard to exclude septic arthritis 1

Diagnostic Injection Strategy

Image-guided anesthetic ± corticosteroid injection is rated 5/9 (may be appropriate) for extra-articular soft tissue abnormalities and 8/9 (usually appropriate) when trying to exclude the hip as pain source 1

Injection Approach

• Ultrasound-guided injection into the iliopsoas bursa can differentiate iliopsoas pathology from intra-articular hip disease 3
• Intra-articular hip injection helps determine if pain originates from the joint versus surrounding soft tissues 1, 3
• Diagnostic injections are safe and provide both therapeutic benefit and diagnostic clarity 1

Clinical Examination Pearls

Key Physical Findings to Assess

• Restricted and painful hip quadrant test has high sensitivity for hip pathology 6
• FABER test (Flexion, Abduction, External Rotation) was positive in 88% of patients with confirmed hip pathology 6
• Pain with resisted hip flexion suggests iliopsoas tendinitis 3
• Palpable inguinal mass with groin pain raises concern for iliopsoas bursitis 4

Common Pitfalls to Avoid

• Do not skip plain radiographs - they are mandatory first-line imaging even when ultrasound shows soft tissue abnormalities 1
• Avoid MRI with and without IV contrast as routine protocol - it receives lower appropriateness ratings (2-5/9) and adds unnecessary cost without improving diagnostic yield for soft tissue edema 1
• Do not rely solely on ultrasound for complete evaluation - while US is rated 7/9 for tendinitis detection, it has limited ability to assess intra-articular structures and deep soft tissues 1
• Consider referred pain sources - spine, sacroiliac joint, gynecologic, and gastrointestinal pathology can all cause groin pain 3, 6
• Negative MRI does not exclude hip pathology - if clinical suspicion remains high, consider hip arthroscopy as the definitive diagnostic procedure 6

Treatment Considerations Based on Etiology

For Iliopsoas Bursitis

• Systemic corticosteroid therapy (e.g., 25 mg/day prednisone) can resolve symptoms when bursa is not communicating with hip joint 4
• Lack of communication between hip joint and bursa is a favorable prognostic indicator 4

For Tendinopathy

• High-grade joint mobilization combined with targeted exercise programs can improve range of motion and reduce pain 7
• Physical therapy should address hip flexion, abduction, and external rotation deficits 7

For Ischiofemoral Impingement

• Ischiofemoral space <16 mm and quadratus femoris space <9.5 mm are diagnostic thresholds on MRI 5
• This diagnosis should be considered when other causes of groin pain are excluded 5