Do knee joint dislocations often spontaneously relocate?

Knee Joint Dislocations and Spontaneous Relocation

Yes, knee joint dislocations frequently spontaneously relocate before clinical presentation, making them potentially dangerous injuries that can be missed if clinicians are not vigilant. 1, 2

Clinical Reality of Spontaneous Reduction

• Spontaneous reduction is common enough that it represents a significant diagnostic challenge, as patients may present with a reduced knee joint on examination despite having sustained a true dislocation 1, 2
• The knee may appear grossly normal on initial evaluation despite severe multiligamentous injury, requiring a high index of suspicion based on mechanism of injury and clinical findings 3, 2
• Not all knee dislocations are diagnosed on plain radiographs after spontaneous reduction, emphasizing the need for clinical vigilance 3

Critical Implications of Missed Spontaneously Reduced Dislocations

• Knee dislocations that reduce spontaneously are potentially dangerous injuries that can result in amputation due to missed secondary vascular injury 1
• Approximately 30% of patients with posterior knee dislocation have popliteal artery injury requiring prompt surgical intervention for limb preservation 4, 5
• Peroneal and tibial nerve injuries occur frequently and cause significant long-term morbidity 4, 5

Immediate Assessment Protocol for Suspected Spontaneously Reduced Dislocation

When spontaneous reduction is suspected based on mechanism or clinical presentation:

• Immediately assess vascular status by checking for absent pulses, pallor, cool extremity, or delayed capillary refill, as popliteal artery injury is limb-threatening 5
• Evaluate neurological function, specifically testing peroneal and tibial nerve function 5
• Obtain anteroposterior and lateral radiographs as the initial imaging study, even if the knee appears reduced, looking for fractures, joint space abnormalities, and signs of dislocation 5, 6
• Order CTA of the lower extremity immediately if any signs of vascular compromise are present, as CTA has similarly high accuracy to conventional angiography but is less invasive 4, 5

Advanced Imaging After Initial Evaluation

• Order MRI without IV contrast after initial radiographs to evaluate the extent of multiligamentous injury, meniscal tears, and occult fractures, as MRI accurately evaluates soft-tissue, osseous, and neural injuries after knee dislocation 5, 4
• Consider CT without contrast for better characterization of complex fractures, particularly tibial plateau fractures identified on radiographs 5

Critical Pitfalls to Avoid

• Never assume a reduced knee joint rules out dislocation—the history and mechanism of injury should guide suspicion 3, 1, 2
• Do not delay vascular imaging if any concern for arterial injury exists, as time to revascularization is critical for limb salvage 5
• Physician judgment should supersede clinical decision rules when gross deformity was reported or when mechanism suggests high-energy trauma 4, 6
• Recognize that most patients will have some long-term functional limitation despite optimal treatment, and early multidisciplinary specialist care is required 3