What is the appropriate emergency management for a pediatric knee dislocation?

Emergency Management of Pediatric Knee Dislocation

Immediately reduce the knee dislocation in the emergency department, assess for vascular injury with ankle-brachial indices, obtain CTA if vascular compromise is suspected, and immobilize with a splint for discharge with urgent orthopedic follow-up. 1, 2

Immediate Reduction Protocol

• Perform closed reduction immediately upon diagnosis without waiting for imaging, as time to reduction is critical for limb preservation 2, 3
• Reduction should be performed in the emergency department setting as soon as the dislocation is identified 2
• After reduction, immobilize the knee in 15-20 degrees of flexion using a splint rather than a cast to allow for ongoing neurovascular monitoring 4

Critical Vascular Assessment

Vascular injury occurs in approximately 30% of posterior knee dislocations and represents a limb-threatening emergency requiring immediate intervention. 4, 1

• Check for absent pulses, pallor, cool extremity, or delayed capillary refill immediately after reduction 1
• Obtain ankle-brachial indices (ABI) on all patients—normal pulses do not exclude vascular injury 2
• If ABI is abnormal (<0.9) or any signs of vascular compromise exist, order CTA of the lower extremity immediately 4, 1, 2
• CTA is less invasive than conventional angiography with similarly high accuracy for detecting popliteal artery injuries 4, 1
• Do not delay vascular imaging if any concern for arterial injury exists, as time to revascularization is critical for limb salvage 1

Neurological Evaluation

• Test for peroneal nerve injury (foot drop, numbness over dorsum of foot) and tibial nerve injury (inability to plantarflex, numbness on sole) 4, 1
• Document neurological status before and after reduction, as nerve injuries cause significant long-term morbidity 4, 1

Initial Imaging Protocol

• Obtain anteroposterior and lateral radiographs after reduction to identify fractures, joint space abnormalities, and confirm adequate reduction 4, 1, 5
• Radiographs should be obtained in all pediatric knee dislocations regardless of age, as fracture patterns differ from adults 4
• If complex fractures (particularly tibial plateau) are identified, consider CT without contrast for better characterization 1, 5

Disposition and Follow-up Planning

• Most pediatric knee dislocations can be managed as day surgery cases if admission is required, with reduction performed in the emergency department 4
• Discharge with knee immobilization in a removable splint to allow for serial neurovascular checks 4
• Arrange urgent orthopedic follow-up within 24-48 hours for definitive ligamentous injury assessment 4, 2
• MRI without IV contrast should be obtained after discharge (not emergently) to evaluate multiligamentous injury, meniscal tears, and occult fractures 1, 5
• Do not order MRI with IV contrast, as non-contrast MRI is sufficient and appropriate 1

Critical Pitfalls to Avoid

• Do not assume normal pulses exclude vascular injury—50% of knee dislocations spontaneously reduce before ED arrival, making diagnosis more challenging 2, 6
• Do not delay reduction to obtain pre-reduction imaging unless there is concern for an irreducible dislocation 2
• Do not use rigid casts initially, as they prevent ongoing neurovascular monitoring 4
• Avoid keeping the knee in full extension during immobilization, as this increases tension on neurovascular structures 4