• Knee (tibiofemoral) dislocation is a limb-threatening emergency that may appear anatomically normal at ED presentation due to spontaneous reduction occurring in up to 50% of patients.
• A knee dislocation can injure the popliteal artery, resulting in limb ischemia.
• A spontaneous reduction does not decrease the likelihood of vascular injury.

• The most common types are anterior (hyperextension injury) and posterior dislocations (high energy impact to flexed knee). Posterior dislocation is the most common type to injure the popliteal artery. Others include medial, lateral and rotary dislocations.
• Risk factors:
  • High-energy trauma (e.g., dashboard impact in MVC, ground-level fall in patients with severely elevated BMI).
  • Morbid obesity
•  Complications:
  • Immediate
    • Popliteal artery injury
    • Geniculate artery injury
    • Limb Ischemia
    • Ligamentous injury
    • Joint capsule rupture
    • Muscle and tendon injury

• • Delayed
    • Compartment syndrome
    • Arterial thrombosis
    • DVT
    • Pseudoaneurysm
    • Heterotopic ossification

• Knee dislocation is a clinical diagnosis supplemented with imaging as needed.
• Perform a history (focused on mechanism and risk factors) and physical exam, including a detailed neurovascular assessment (see Table 1).

Table 1. Physical exam findings of knee dislocation.

*Indicative of posterolateral dislocation (see Recommended Treatment).

• Initial imaging includes radiographs +/- CT if there is diagnostic uncertainty. Apply the Ottawa Knee Rule as appropriate.
• If a knee dislocation is diagnosed or suspicion is moderate-high, the workup is focused on identifying vascular injury (see Table 2).

Table 2. Diagnostic tests for vascular injury in knee dislocation.

*If the pretest probability increases to medium or high during this 24-hour period, CT-angiography or surgical exploration, respectively, is indicated. Furthermore, the recommendation of ABI and serial exams is based on low-quality and emerging evidence cited in Rosen’s. It may be useful in centres without access to CT for risk stratification before transfer. CT-angiography is the gold standard test.

• Emergent closed reduction (procedural sedation). Assess and document neurovascular status pre- and post-. Obtain post-reduction radiographs. Manipulation risks worsening vascular injury; however, the benefits of reduction outweigh the risks. Exception: posterolateral dislocations require open reduction, as closed reduction is impossible due to the anatomy of the dislocation.
• Reduction technique: one clinician stabilizes the distal femur while the other manipulates the tibia. Apply longitudinal traction to the tibia and, if necessary, translate/rotate in the opposite direction of dislocation.
  • Anterior: traction, lift distal femur anteriorly while pushing tibia posteriorly.
  • Posterior: traction, push distal femur posteriorly while lifting tibia anteriorly.
  • Medial/lateral: traction, medial or lateral translation.
  • Rotary: traction, rotation in the opposite direction of deformity.
• If reduction is unsuccessful, emergent orthopedic consultation is indicated to attempt closed reduction in the ED or proceed to open reduction in the OR.
• Immobilize knee in long leg posterior splint at 15 to 20 degrees of flexion at the knee.
• Serial neurovascular assessments.
• Emergent orthopedic +/- vascular surgery consultation if concern for vascular injury

Patients with diagnosed or suspected knee dislocation should generally be admitted to hospital.

• Patients with an isolated knee dislocation should be transferred to a centre with orthopedic and vascular surgical capabilities.
• Patients with a knee dislocation in the context of multisystem trauma should be transferred to a trauma referral centre.
• Attempt knee reduction before transfer.

1. Davenport M and Franco VS. Knee and Lower Leg Injuries. In: Walls RM, Hockberger RS, Gausche-Hill M, Erickson TB, Wilcox SR, editors. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia (US): Elsevier; 2023. p. 602-622.

   
   

2. Bengtzen R. Knee Injuries. In: Tintinalli JE, Ma O, Yealy DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH, editors. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide [Internet]. 9th ed. United States: McGraw Hill Medical; 2020 [cited 2023 June 9]. Chapter 274. Available from: https://accessmedicine.mhmedical.com/content.aspx?sectionid=222407442&bookid=2353#226634422

   
   

3. Bachman MC. 2022. Knee (tibiofemoral) dislocation and reduction. UpToDate. Retrieved June 6, 2023, from https://www.uptodate.com/contents/knee-tibiofemoral-dislocation-and-reduction?search=knee%20dislocation%20reduction&source=search_result&selectedTitle=1~2&usage_type=default&display_rank=1#H7