AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

Knee dislocation is a relatively rare injury but an important one to recognize because coexistent vascular injury, if missed, often leads to limb loss. In addition, knee dislocation often presents in the context of multisystem trauma or spontaneous relocation, which makes detection more difficult.

CLINICAL

Section 3 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

History

Knee dislocation is classified according to the position of the tibia relative to the femur. The 5 major types of dislocation, which are illustrated in Media file 1, are as follows:

• Anterior: Anterior dislocation often is caused by severe knee hyperextension. Cadaver research has shown that approximately 30 degrees of hyperextension is required before dislocation will occur.
• Posterior: Posterior dislocation occurs with anterior-to-posterior force to the proximal tibia, such as a dashboard type of injury or a high-energy fall on a flexed knee. Media file 2 shows a radiograph of a posterior dislocation.
• Medial, lateral, or rotatory: Medial, lateral, and rotatory dislocations require varus, valgus, or rotatory components of applied force. A lateral dislocation is illustrated in Media file 3.
• More than half of all dislocations are anterior or posterior, and both of these have a high incidence of popliteal artery injury. Twenty to thirty percent of all knee dislocations are complicated further by open joint injury (see Media file 4).

Physical

• Most often, the affected limb has a gross deformity around the knee with swelling and immobility. Occasionally, the knee will have relocated spontaneously prior to the patient's arrival at the ED. This makes a careful physical examination very important. The finding of varus or valgus instability in full extension of the knee is suggestive of a grossly unstable knee and of a spontaneously reduced dislocation. In addition, pain out of proportion or absent or decreased pulse should be red flags of such an injury. The above also underscores the importance of joint and vascular examinations, especially in patients with head injuries or in those who are intoxicated and may not be able to communicate symptoms adequately.
• A careful vascular examination is essential, as popliteal artery injury occurs in 7-45% of all knee dislocations. The popliteal artery may be damaged severely in both closed and open dislocations, and such injury must be ruled out in knees that have relocated spontaneously. Palpation of the dorsalis pedis and posterior tibial arteries along with capillary refill evaluation is necessary. The presence of normal pulses does not rule out the presence of significant vascular injury. Coexistent peroneal nerve injury occurs in 25-35% of patients and manifests with decreased sensation at the first webspace with impaired dorsiflexion of the foot.

Causes

• The knee is a very stable joint requiring high-energy trauma to produce dislocation. At least 3 major ligaments must rupture for dislocation to occur. Common mechanisms of injury include the following:
• • Motor vehicle collisions
  • Auto-pedestrian impact
  • Industrial injuries
  • Falls
  • Athletic injuries

DIFFERENTIALS

Section 4 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

WORKUP

Section 5 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Imaging Studies

• Plain radiographs
• Arteriogram
• Duplex scanning
• Ankle-brachial index

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Prehospital Care

• Prehospital personnel should splint the extremity and provide rapid transport to a medical facility.
• Perform field reduction for patients with evidence of vascular compromise.

Emergency Department Care

• Reduction procedures
• • Do not delay reduction in limbs with obvious vascular impairment. Only patients with good peripheral pulses should undergo prereduction radiographs.
  • Reduction is straightforward and often easily accomplished in the ED. After adequate sedation, longitudinal traction will relocate the majority of knee dislocations. A postreduction lateral knee dislocation is shown in Media file 5. Posterolateral dislocations are particularly difficult and often require operative reduction.
  • After reduction, splint the lower extremity, apply ice, and keep the knee elevated.

Consultations

Always consult an orthopedic surgeon. In addition, strongly consider consulting a vascular surgeon, as many patients have significant vascular injury.

MEDICATION

Section 7 of 11  

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• References

NSAIDs, analgesics, and anxiolytics are used to treat the pain associated with dislocations.

Drug Category: Analgesics

Pain control is essential to quality patient care. It ensures patient comfort, promotes pulmonary toilet, and aids physical therapy regimens. Many analgesics have sedating properties that benefit patients with injuries.

Drug Category: Anxiolytics

Patients with painful injuries usually experience significant anxiety. Anxiolytics allow the clinician to administer a smaller analgesic dose to achieve the same effect.

Drug Category: Nonsteroidal anti-inflammatory agents (NSAIDs)

These agents are used most commonly for the relief of mild to moderately severe pain. Although the effects of NSAIDs in the treatment of pain tend to be patient specific, ibuprofen is usually the DOC for initial therapy. Other options include flurbiprofen, ketoprofen, and naproxen.

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Further Inpatient Care

• Vascular examination findings may be normal in the presence of significant popliteal artery injury. Most authors used to recommend mandatory arteriograms or operative exploration for all knee dislocations, but recent literature has questioned the need for this. Recent studies have shown good vascular assessment with the ankle-brachial index, Duplex scanning, or both. Briefly, the ankle-brachial index compares the Doppler pressure of an arm to a leg to screen for lower limb ischemia. This straightforward measurement is performed by recording the highest Doppler sound of the brachial pulse and comparing it to the highest Doppler sound of the posterior tibial or dorsalis pedis artery. The ankle Doppler pressure is then divided by the brachial Doppler pressure to calculate the index. Indexes less than 0.9 indicate an abnormal result.
• Time is of utmost concern, as vascular repair more than 8 hours after injury carries an amputation rate of greater than 80%. In contrast, operative vascular repair within 8 hours of injury yields a limb-salvage rate of 80%.
• The repair of coexistent popliteal vein injury is controversial. Fasciotomy is recommended after vascular repair, as severe swelling and development of compartment syndrome are common in the postoperative phase.
• Operative repair of nerve injury remains controversial, as a poor prognosis is common with both operative and nonoperative care.
• Operative ligamentous repair is recommended by most authors, as functional results are better than those of nonoperative care.

Transfer

• Patients considered for transfer should have undergone emergency reduction of the knee dislocation. Since time is crucial in salvaging the limb after a vascular injury, transfer should be initiated only if vascular consultation and/or evaluation are not available at the transferring institution or if an arteriogram has been performed and results are normal.

Complications

• Popliteal artery injury
• Popliteal vein injury
• Peroneal nerve injury
• Ligamentous injury
• Compartment syndrome

Prognosis

• When treated expeditiously and appropriately, 60-70% of patients will have a painless, stable knee. Of the remaining patients, one half will eventually have reasonable function, while the other half will have a chronically unstable and painful knee.

Patient Education

• For excellent patient education resources, visit eMedicine's Breaks, Fractures, and Dislocations Center. Also, see eMedicine's patient education article, Knee Dislocation.

MISCELLANEOUS

Section 9 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Medical/Legal Pitfalls

• Failure to perform reduction expeditiously
• Failure to consider an associated vascular injury
• Failure to recognize a spontaneously reduced dislocation

Special Concerns

• Knee dislocation is a serious limb-threatening injury that needs to be recognized and treated expeditiously. The possibility of vascular injury must be pursued actively, as it contributes significantly to the morbidity associated with this disorder.

MULTIMEDIA

Section 10 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Media file 1:  Types of knee dislocation.
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Media type:  Image

Media file 2:  Posterior knee dislocation.
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Media type:  X-RAY

Media file 3:  Lateral knee dislocation.
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Media type:  Photo

Media file 4:  Open knee dislocation.
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Media file 5:  Lateral knee dislocation after reduction (same patient as in Image 2).
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Media type:  Photo

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

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• Chhabra A, Cha PS, Rihn JA, Cole B, Bennett CH, Waltrip RL. Surgical management of knee dislocations. Surgical technique. J Bone Joint Surg Am. Mar 2005;87 Suppl 1(Pt 1):1-21. [Medline].
• Cone JB. Vascular injury associated with fracture-dislocations of the lower extremity. Clin Orthop. Jun 1989;(243):30-5. [Medline].
• Dennis JW, Jagger C, Butcher JL, et al. Reassessing the role of arteriograms in the management of posterior knee dislocations. J Trauma. Nov 1993;35(5):692-5; discussion 695-7. [Medline].
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• Mills WJ, Barei DP, McNair P. The value of the ankle-brachial index for diagnosing arterial injury after knee dislocation: a prospective study. J Trauma. Jun 2004;56(6):1261-5. [Medline].
• Rihn JA, Groff YJ, Harner CD, Cha PS. The acutely dislocated knee: evaluation and management. J Am Acad Orthop Surg. Sep-Oct 2004;12(5):334-46. [Medline].
• Rihn JA, Groff YJ, Harner CD, Cha PS. The acutely dislocated knee: evaluation and management. J Am Acad Orthop Surg. Sep-Oct 2004;12(5):334-46. [Medline].
• Robertson A, Nutton RW, Keating JF. Dislocation of the knee. J Bone Joint Surg Br. Jun 2006;88(6):706-11. [Medline].
• Rockwood CA, Green DP, Bucholz RW. Injuries of the knee. In: Fractures in Adults. Vol 2. Lippincott Williams & Wilkins Publishers; 1996:2112-2126.
• Stannard JP, Sheils TM, Lopez-Ben RR, McGwin G Jr, Robinson JT, Volgas DA. Vascular injuries in knee dislocations: the role of physical examination in determining the need for arteriography. J Bone Joint Surg Am. May 2004;86-A(5):910-5. [Medline].
• Varnell RM, Coldwell DM, Sangeorzan BJ, Johansen KH. Arterial injury complicating knee disruption. Third place winner: Conrad Jobstaward. Am Surg. Dec 1989;55(12):699-704. [Medline].
• Welling RE, Kakkasseril J, Cranley JJ. Complete dislocations of the knee with popliteal vascular injury. J Trauma. Jun 1981;21(6):450-3. [Medline].

Article Last Updated: Nov 29, 2007