What is the differential diagnosis (ddx) and work-up for a 17-year-old female with hip pain?

Hip Pain in a 17-Year-Old Female: Differential Diagnosis and Work-Up

Immediate Red Flag Exclusions

First, you must immediately rule out slipped capital femoral epiphysis (SCFE), infection, tumors, and stress fractures before considering other diagnoses in this adolescent patient 1, 2. These conditions can cause permanent disability or death if missed.

Critical Red Flags Requiring Urgent Evaluation:

• SCFE: Can present deceptively as medial thigh or knee pain rather than hip pain, with external rotation deformity of the affected limb 1, 2
• Infection (septic arthritis/osteomyelitis): Acute onset, fever, inability to bear weight, severe pain at rest 2
• Stress fractures: Insidious onset, night pain, inability to bear weight, focal bone tenderness 2
• Tumors: Night pain, constitutional symptoms (fever, weight loss), progressive worsening 2
• Perthes disease: Must be excluded in this age group as a serious pathological condition 1

Primary Differential Diagnoses by Pain Location

Anterior Hip/Groin Pain (Most Common in This Age):

• Femoroacetabular impingement (FAI) syndrome: Groin pain with hip flexion, adduction, and internal rotation; associated with cam, pincer, or mixed morphology on imaging 3, 1, 2
• Acetabular labral tears: Sharp, catching pain in groin/medial hip with mechanical symptoms; often coexists with FAI or dysplasia 2
• Acetabular dysplasia/hip instability: Misalignment between femoral head and acetabulum causing instability and rim overload during normal activities 3, 1, 2
• Iliopsoas tendinopathy: Anterior/medial groin pain with pain on hip flexion against resistance 2

Lateral Hip Pain:

• Greater trochanteric pain syndrome: Lateral hip pain with tenderness over greater trochanter 4, 5

Posterior Hip Pain:

• Lumbar spine pathology (referred pain): Sharp lancinating pain radiating down the leg, induced by sitting/standing/walking, often present at rest and improved by position change 1, 2
• Sacroiliac joint dysfunction: Pain referred to groin/medial hip with SI joint tenderness 2

Diagnostic Algorithm

Step 1: History Assessment

• Determine red flag presence: Night pain, constitutional symptoms (fever, weight loss), inability to bear weight, external rotation deformity 1, 2
• Pain location: Anterior/groin, lateral, or posterior 6, 5
• Pain characteristics: Activity-related vs. present at rest, mechanical symptoms (catching, locking), instability sensation 2
• Onset: Sudden vs. insidious 6

Step 2: Physical Examination

• FADIR test (flexion-adduction-internal rotation): A negative test helps rule out hip-related pain, though clinical utility is limited 3, 1
• Hip range of motion: Assess internal rotation limitation (suggests intra-articular pathology) 2, 5
• Trendelenburg test: Evaluates gluteus medius/minimus function 4
• Mandatory lumbar spine screening: Required in ALL cases to exclude referred pain 3, 1, 2
• Assess gait: External rotation deformity suggests SCFE 1, 2

Step 3: Imaging Protocol

Initial imaging should include AP pelvis and lateral femoral head-neck radiographs (Dunn view, frog-leg view, or cross-table view) 3, 2. This provides understanding of underlying hip morphology and excludes SCFE, fractures, and tumors 3, 4.

Advanced imaging indications:

• MRI/MRA or CT arthrogram: When assessing intra-articular structures (labrum, cartilage, ligamentum teres) or when radiographs are inconclusive 3, 2
• MRI without contrast: If Trendelenburg gait persists or symptoms are refractory, to evaluate for abductor tendon tears 4

Critical Clinical Pitfalls to Avoid

• Hip pathology frequently presents as knee pain: SCFE commonly presents as medial thigh or knee pain rather than hip pain 1, 2
• Spine pathology can present as hip pain: Always screen the lumbar spine as a competing musculoskeletal source 1, 2
• Incidental imaging findings are extremely common in asymptomatic adolescent athletes: Clinical correlation is mandatory; never diagnose based on imaging alone 3, 1
• Coexisting pathology is common: Labral tears often coexist with FAI or dysplasia 2
• Clinical examination tests have good sensitivity but poor specificity: A comprehensive approach combining symptoms, clinical signs, and imaging is essential 3, 1