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An Unusual Case of Knee Pain and Swelling:�MSK Ultrasound to the Rescue

Nehemesis Rivera Ortiz MD, Miguel F. Agrait González MD

Ponce Health Sciences University Emergency Medicine Residency

  • 25 y/o male presented to the emergency department with R knee pain and swelling
  • Crush injury to the knee 1 week earlier
  • Seen in ED immediately after incident, had normal XR and was discharged
  • Swelling particularly on medial aspect progressively worsened
  • Pain unrelieved by OTC medications
    • Worse with ambulation and deep flexion
  • No previous similar issues or prior knee injuries 

History

R Knee

  • Observation: obvious medial swelling (1a,1b), no open wounds
  • RoM: pain with both passive and active flexion and extension
  • Palpation: Significant TTP on medial aspect with obvious fluctuance and fluid collection/effusion, No TTP across joint line, quad/patellar tendons
  • NV: 5/5 strength in leg extension at knee, plantar flexion and dorsiflexion of foot
  • Special: normal Lachman, no gapping with valgus/varus stress 

Physical Exam

1a

1b

Imaging Results

  • Increasing pain and swelling
  • Concern for internal derangement or occult fracture
  • XR unremarkable (2a)
  • MSK ultrasound without intraarticular effusion (2b)
    • Shows large fluid collection between fat and fascial plane (2c-d)
  • Consistent with Morel Lavallée lesion or internal degloving injury
  • Once diagnosis confirmed, decision is made to drain the fluid in the ED
  • 60 mL of thin, bloody fluid obtained (scan QR code for video and
  • Compressive dressing applied 

Clinical Course

2a

2b

2c

2d

Skin and Subcutaneous

Fat Pad (normal)

Quad Tendon

Ultrasound showing large fluid collection below subcutaneous tissue

Needle Drainage

Post Drainage

60 mL fluid collected

  • MLL are usually missed on initial evaluation
  • Consider ED drainage and compression with close follow up with orthopedics or trauma
  • May need repeat drainage, injection with sclerosing agents, open drainage
  • Can consider admission for more severe injuries
  • MSK Ultrasound can help make diagnosis and prevent misdiagnosis
  • Delayed diagnosis associated to poor outcomes
    • Infection, scarring, chronic pain are all common
    • Necrotizing fasciitis described as possible complication if not drained

Discussion

  • MLL resolved after drainage and compression
  • No further fluid accumulation noted
  • No surgical or additional injection therapy required 

Follow Up

Morel Lavallée Lesion 

Final Diagnosis

  • Consider Morel Lavallée lesions particularly in crush injuries
  • Use MSK ultrasound to distinguish from other similar presentations 

Take Home Points

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