Knee Dislocation
Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.
Title: 5-Minute Orthopaedic Consult, 2nd Edition
Copyright ©2007 Lippincott Williams & Wilkins
> Table of Contents > Knee Dislocation
Knee Dislocation
Gregory Gebauer MD, MS
John H. Wilckens MD
Basics
Description
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Dislocation of the knee is an orthopaedic emergency.
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The most common causes are motor vehicle accidents, followed by sports and falls from heights.
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Classification:
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Anterior
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Posterior
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Medial
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Lateral
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Rotary: Subclassified as anteromedial, anterolateral, posteromedial, posterolateral
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General Prevention
Seat belts and airbags are the best methods of prevention.
Epidemiology
Incidence
Rare
Associated Conditions
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Neurovascular injury, particularly to the popliteal artery or peroneal nerve
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Fractures of the tibia or femur
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Rupture of the collateral and/or cruciate ligaments
Diagnosis
Signs and Symptoms
History
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Classically, patients with knee dislocations present with obvious deformity, swelling, pain, and inability to move the knee.
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Many knee dislocations are reduced before examination by a physician; thus, deformity may not be present.
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It is critical to assess the neurovascular status of all patients with possible knee dislocations because:
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Injury to the popliteal artery occurs in 32–45% of cases (1,2).
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Nerve injury (most commonly the peroneal nerve) occurs in 16–40% of all knee dislocations (3,4).
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Urgent vascular evaluation is required
for absent pulses; ecchymosis in the popliteal fossa; a cold, cyanotic
extremity; or loss of sensorimotor function.
Physical Exam
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Inspect the extremity for obvious deformity, swelling, and ecchymosis.
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Perform a thorough neurovascular examination.
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Palpate pulses or assess them by Doppler, note warmth of skin, and examine sensory and motor function.
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The presence of pulses does not rule out vascular injury because an intimal flap tear of the vessel may be present.
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Any sign of vascular injury necessitates an emergent vascular surgery consultation.
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Examination for laxity of the knee should
be performed systematically for injury to any of the 4 knee ligaments
(ACL, OSD, MCL, or LCL). -
Laxity of 2 or more knee ligaments leads to a presumptive diagnosis of knee dislocation.
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Patients should be examined carefully at regular intervals to exclude the possibility of compartment syndrome.
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The most reliable signs for compartment
syndrome are intractable, unrelenting pain out of proportion to the
injury and pain with passive stretch of the ankle and toes.
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Tests
Imaging
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Radiography:
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AP and lateral views of the knee should be obtained, but doing so should not delay reduction of an obvious dislocation.
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MRI:
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May be useful in assessing soft-tissue and ligamentous injury, but it should not be performed acutely.
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Also allows visualization of the vascular system
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Diagnostic Procedures/Surgery
Any patient with a vascular injury should undergo angiography or MRI.
Differential Diagnosis
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Dislocation of the patella
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Neurovascular injury unrelated to dislocation
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Fracture of the tibia or femur
Treatment
General Measures
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Many knee dislocations are the result of
motor vehicle crashes; therefore, all such patients should be assessed
by a trauma protocol.-
Initial assessment should include evaluation of airway, breathing, circulation, and vital signs.
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Immediate reduction is recommended.
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Anterior dislocations are reduced with longitudinal traction and the lifting of the femur anteriorly.
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Posterior dislocations are reduced with
longitudinal traction and the lifting upward of the proximal tibia
while extending the knee. -
Medial and lateral dislocations are
reduced with longitudinal traction and the appropriate medial or
lateral pressure on the tibia and femur.
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The neurovascular status should be assessed before and after reduction.
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Orthopaedic and vascular surgeons should be notified.
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The knee should be immobilized in a
splint or spanning external fixator, with careful attention to the
neurovascular status and the development of compartment syndrome. -
Nonoperative treatment:
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Indicated for patients who are sedentary or elderly or who have substantial comorbidities preventing surgical repair.
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A splint should be followed by 6–8 weeks of protected immobilization.
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Activity
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Nonoperatively treated patients:
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6–8 weeks of protected immobilization
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May begin quadriceps setting exercises in the splint, followed by active leg-lifting exercises after the immobilizer is removed
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Operatively treated patients:
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Activity is determined by which structures were injured, repaired, and reconstructed.
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After 6 weeks, patients may begin active ROM exercises.
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Average return to previous activity for both treatments:
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Sports, 9–12 months
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Sedentary jobs, 2 months
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Heavy labor, 6–9 months
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P.213
Special Therapy
Physical Therapy
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ROM and strengthening exercises should be started after immobilization.
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Quadriceps setting exercises can begin in the splint/fixator.
Medication
First Line
Narcotics
Surgery
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Emergent surgery is required for patients with vascular injury; saphenous vein grafting often is required.
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Fasciotomies may be required for patients with prolonged ischemic time or with compartment syndrome.
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Open dislocation requires immediate surgical intervention.
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Definitive surgical repair usually is
performed 10–14 days after the injury, to allow swelling to diminish
and to facilitate arthroscopic procedures. -
Methods of repair and reconstruction depend on the extent and nature of the injuries.
Follow-up
Disposition
Patients should be followed at 4–6-week intervals until they achieve maximum recovery.
Issues for Referral
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An orthopaedic surgeon should be consulted emergently.
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Any vascular injuries require immediate consultation with a vascular surgeon.
Prognosis
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Prognosis depends on the associated limb injuries and the interventions for those injuries.
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Viability of the limb in the presence of
vascular compromise is directly related to the time between injury and
revascularization. -
The most common residual effects are arthrofibrosis (knee stiffness) and postoperative arthritis.
Complications
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Loss of limb:
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Usually secondary to prolonged ischemia
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The amputation rate is 86% when ischemia lasts >8 hours (1).
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Arthrofibrosis (stiff knee):
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In nonoperative treatment, residual stiffness provides stability for injured ligaments.
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Operative treatment may increase the incidence of arthrofibrosis unless reconstruction is strong enough to allow early ROM.
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Neurologic deficit:
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Nerve injury, most often the peroneal nerve, is a common sequela of knee dislocation.
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Recovery may take months to years, and prognosis varies.
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Knee instability:
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Secondary to injury to the ligamentous structures
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Redislocation is rare.
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Posttraumatic arthritis:
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Secondary to cartilage injury during the trauma
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Can lead to long-term disability
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References
1. Green NE, Allen BL. Vascular injuries associated with dislocation of the knee. J Bone Joint Surg 1977;59A:236–239.
2. Jones RE, Smith EC, Bone GE. Vascular and orthopaedic complications of knee dislocation. Surg Gynecol Obstet 1979;149:554–558.
3. Almekinders LC, Logan TC. Results following treatment of traumatic dislocations of the knee joint. Clin Orthop Relat Res 1992;284:203–207.
4. Welling RE, Kakkasseril J, Cranley JJ. Complete dislocations of the knee with popliteal vascular injury. J Trauma 1981;21:450–453.
Additional Reading
Giannoulias CS, Freedman KB. Knee dislocations: management of the multiligament-injured knee. Am J Orthop 2004;33:553–559.
Rihn JA, Groff YJ, Harner CD, et al. The acutely dislocated knee: evaluation and management. J Am Acad Orthop Surg 2004;12:334–346.
Schenck RC Jr, ed. Multiple Ligamentous Injuries of the Knee in the Athlete. Rosemont, IL: American Academy of Orthopaedic Surgeons, 2002.
Stannard
JP, Sheils TM, Lopez-Ben RR, et al. Vascular injuries in knee
dislocations: the role of physical examination in determining the need
for arteriography. J Bone Joint Surg 2004;86A: 910–915.
JP, Sheils TM, Lopez-Ben RR, et al. Vascular injuries in knee
dislocations: the role of physical examination in determining the need
for arteriography. J Bone Joint Surg 2004;86A: 910–915.
Wong
CH, Tan JL, Chang HC, et al. Knee dislocations—a retrospective study
comparing operative versus closed immobilization treatment outcomes. Knee Surg Sports Traumatol Arthrosc 2004;12:540–544.
CH, Tan JL, Chang HC, et al. Knee dislocations—a retrospective study
comparing operative versus closed immobilization treatment outcomes. Knee Surg Sports Traumatol Arthrosc 2004;12:540–544.
Miscellaneous
Codes
ICD9-CM
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836.5 Closed knee dislocation
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836.6 Open knee dislocation
Patient Teaching
Activity
Emphasize ROM and, later, strengthening exercises.
FAQ
Q: Do all patients with a knee dislocation require an arterial study to document the status of the popliteal artery?
A:
No. Although as many as 50% of knee dislocations from high-energy motor
vehicle accidents have a popliteal artery injury, <10% of athletic
knee dislocations have an arterial injury. Patients with diminished
distal pulses before surgical evaluation require urgent vascular
consultation.
No. Although as many as 50% of knee dislocations from high-energy motor
vehicle accidents have a popliteal artery injury, <10% of athletic
knee dislocations have an arterial injury. Patients with diminished
distal pulses before surgical evaluation require urgent vascular
consultation.