What is the immediate management for a traumatic knee joint dislocation that has spontaneously relocated in an adult or adolescent patient?

Immediate Management of Spontaneously Reduced Traumatic Knee Dislocation

For a traumatic knee dislocation that has spontaneously relocated, immediately assess neurovascular status and obtain plain radiographs, followed by CTA of the lower extremity if any signs of vascular compromise are present, as popliteal artery injury occurs in approximately 30% of posterior knee dislocations and requires urgent surgical intervention. 1, 2

Critical Initial Assessment (Within Minutes)

Neurovascular Examination - Highest Priority

• Assess vascular status immediately: Check for absent pulses, pallor, cool extremity, or delayed capillary refill, as popliteal artery injury is limb-threatening and requires emergent intervention 1, 3
• Evaluate neurological function: Test for peroneal and tibial nerve injuries, which cause significant morbidity and affect long-term limb functionality 1, 4
• Continue serial neurovascular assessments: Reassess routinely for several days after injury, as complications can develop in a delayed fashion 4

Critical pitfall: Many knee dislocations spontaneously reduce before examination, so a high index of suspicion is required based on mechanism of injury and clinical findings—not all dislocations are visible on plain radiographs 5

Immediate Imaging Protocol

Plain Radiographs First

• Obtain anteroposterior and lateral views (lateral with knee at 25-30 degrees flexion) as the initial imaging study 1, 2, 3
• Look for fractures, joint space abnormalities, and signs of dislocation 2, 3

Vascular Imaging - Do Not Delay

• Order CTA of the lower extremity immediately if any of the following are present: 1, 2, 3
  • Absent or diminished pulses
  • Pallor or coolness of the extremity
  • Neurological deficits suggesting vascular compromise
  • High-energy mechanism (motor vehicle accident)
• CTA is less invasive than conventional angiography with similarly high accuracy for detecting popliteal artery injuries 1
• Alternative: MRA can be performed simultaneously with MRI for evaluation of vascular injuries with less morbidity than conventional angiography, showing complete agreement with angiography in detecting popliteal artery injuries 1

Subsequent Advanced Imaging

MRI Without Contrast

• Order MRI without IV contrast after initial radiographs to evaluate the extent of multiligamentous injury, meniscal tears, and occult fractures 2, 3
• MRI is accurate for evaluating soft-tissue, osseous, and neural injuries after knee dislocation 1
• Do not add IV contrast—it provides no additional diagnostic value for ligamentous or meniscal injuries 3

CT Considerations

• Consider CT without contrast for better characterization of complex fractures, particularly tibial plateau fractures identified on radiographs 1, 3

Initial Stabilization and Treatment

Immediate Interventions

• Immobilize the knee in a position of comfort, typically in slight flexion 4
• Maintain non-weight-bearing status until vascular injury is ruled out and stability is assessed 3
• Prepare for urgent surgical intervention if vascular injury is confirmed—arterial injuries must be repaired first to preserve limb viability 1, 6

Damage Control Strategy

• In hemodynamically unstable patients with severe limb trauma, apply damage control principles with temporary stabilization by external fixators rather than definitive osteosynthesis 1
• Schedule delayed definitive surgery once clinical stability is achieved, ideally within 36-48 hours to 2 weeks 1

Definitive Management Planning

Surgical Repair

• Early surgical repair of all damaged structures (vascular, ligamentous, meniscal) is associated with the best functional outcomes, with 55% achieving satisfactory results 7
• Nonoperative treatment results in 100% unsatisfactory outcomes with persistent instability 7
• Most patients require multidisciplinary specialist care including vascular surgery and orthopedics 5

Expected Complications and Sequelae

• Peroneal nerve palsy occurs in 23% of cases 7
• Popliteal artery disruption occurs in 7.5-30% of cases 1, 7
• Long-term sequelae include instability (85%), limp (50%), and high prevalence of post-traumatic osteoarthritis despite good short-term functional outcomes 8, 7

Common Pitfalls to Avoid

• Never assume the knee is stable just because it spontaneously reduced—multiligamentous injury is present in virtually all cases 4, 5
• Do not delay vascular imaging if any concern for arterial injury exists—time to revascularization is critical for limb salvage 1, 6
• Do not discharge without serial neurovascular checks—complications can develop hours to days after initial injury 4
• Do not order MRI with IV contrast for routine evaluation—non-contrast MRI is sufficient and appropriate 3