What is the initial approach to examining a patient with bilateral thigh pain and knee swelling/bruising after a traumatic injury with a popping noise?

Initial Approach to Examining a Patient with Bilateral Thigh Pain and Knee Swelling/Bruising After Traumatic Injury

For a patient with bilateral thigh pain associated with a popping noise, knee swelling, and bruising, radiographs should be the initial imaging modality following a focused physical examination to assess for fracture or other significant structural damage. 1

Physical Examination Components

1. Observation

• Compare both knees for:
  • Extent and pattern of swelling (localized vs. diffuse)
  • Bruising distribution
  • Deformity
  • Patellar position and alignment

2. Palpation

• Assess for:
  • Joint line tenderness (medial and lateral)
  • Patellar tenderness
  • Bony tenderness at tibial plateau, femoral condyles, and fibular head
  • Quadriceps and hamstring muscle tenderness
  • Effusion (ballottement test)

3. Range of Motion Testing

• Passive and active knee flexion and extension
• Compare to uninjured side
• Note if patient can flex to 90 degrees (important criterion in Ottawa Knee Rule) 1

4. Stability Testing

• Valgus/varus stress testing for collateral ligament integrity 2
• Lachman test and pivot shift test for anterior cruciate ligament 2
• Posterior drawer test and tibial sag test for posterior cruciate ligament 2
• McMurray's test and Apley's grind test for meniscal injury 2

5. Weight-bearing Assessment

• Determine if patient can bear weight for four steps (key criterion in Ottawa Knee Rule) 1

Imaging Algorithm

1. Initial Imaging: Plain Radiographs

   • Minimum of two views: anteroposterior (AP) and lateral 1
   • Additional views if indicated:
     • Patellofemoral view for suspected patellar fracture/dislocation
     • Cross-table lateral view to detect lipohemarthrosis (sign of intra-articular fracture) 1
     • Oblique views for better visualization of tibial plateau

2. If Radiographs Negative but High Clinical Suspicion Remains:

   • MRI without contrast is the preferred next imaging study for suspected soft tissue injuries (meniscal tears, ligament ruptures) or occult fractures 1, 3
   • CT may be considered if primary concern is for occult fracture 1

Special Considerations

• Hemarthrosis: Rapid swelling within 2 hours of injury (as described in the case) strongly suggests significant internal derangement, most commonly ACL tear or patellar dislocation 4, 5
• Bilateral Involvement: Unusual and requires careful assessment of both limbs and consideration of mechanism (direct blow vs. twisting)
• Popping Sound: Highly suggestive of ligamentous injury, particularly ACL tear 4

Common Pitfalls to Avoid

1. Failing to apply Ottawa Knee Rule appropriately: Radiographs are indicated with any of these findings:

   • Age ≥55 years
   • Isolated patellar tenderness
   • Tenderness at fibular head
   • Inability to flex to 90 degrees
   • Inability to bear weight for four steps 1

2. Premature advanced imaging: Start with radiographs before proceeding to MRI or CT 1, 3

3. Missing associated injuries: Carefully assess for quadriceps or hamstring muscle strains that may accompany knee injuries 6

4. Inadequate examination due to pain: Consider aspiration of significant effusion to improve examination accuracy and patient comfort 5

5. Overlooking gross deformity: In cases with obvious deformity, palpable mass, or penetrating injury, clinical decision rules should not be applied, and radiographs should be obtained immediately 1