Knee Dislocations

Mauricio Kfuri, MD, PhD

James P. Stannard, MD

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Learning Outcomes
• At the end of this presentation, the learners should:

• Understand the mechanisms of injury associated with a knee dislocation;

• Recognize the importance of a comprehensive neurovascular assessment

while dealing with a knee dislocation;

• Develop a rationale for decision making in cases of dislocated knees

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 1
Mechanism of Injury

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High Energy Trauma
Dashboard Mechanism
Direct anterior tibial blow
Posterior tibial translation
Higher likelihood of PCL tear
Popliteal artery contusion
Possible arterial intimal tear

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 Low Energy Trauma
• 29yo, female
• Morbidly obese
• Low energy fall
• Knee dislocation with
• Popliteal artery tear
• Compartment syndrome
• Results in Knee disarticulation
• Be thorough in obese patients
with low energy trauma!

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 2
Diagnosis

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Diagnosis
• History: Mechanism of injury
• Physical exam
• Look for areas of abrasion (anterior tibia)
• Tenderness
• Lower extremity swelling
• Knee effusion
• Knee instability or asymmetrical laxity

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Diagnosis
In a great number of cases the knee is
not dislocated at admission

The majority (50 to 80%) reduce

spontaneously at the scene of trauma

Pay attention to clinical signs: swelling,

effusion, tenderness, instability

It is easy to overlook!
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Knee Radiographs It is easy to overlook!

One should suspect the existence of One should suspect the existence of
a knee dislocation when radiographs a knee dislocation when radiographs
depict asymmetrical joint spaces. depict bony avulsions.

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Associated Injuries
Vascular 5 to 15%

Neurological 20 to 40%

Soft tissues 15 to 35%

Bone 16%

Rihn, 2004 1 Robertson, 2006 2 Natshuhara, 2014 3

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Initial Assessment

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Priorities!!!
•Vascular status of the limb

•Neurologic status of the limb

•Rule out compartment syndrome

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 Vascular Assessment

Repeated clinical assessment of the knee in the first 48 hours

Angiography only for cases with compromise of perfusion

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 After Knee Reduction

Normal Pulse
Abnormal Pulse
Perfusion is normal

Rigorous Bad
Good Perfusion
Follow-up Perfusion

If pulse becomes questionable

Surgical
Arteriography
Exploration
Arteriography

Barnes CJ, 2002 5

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 Vascular Assessment
Ankle Brachial Index
ABI = doppler systolic arterial pressure in injured limb (ankle) / doppler systolic arterial pressure in

uninjured limb (brachial)

ABI < 0.90

Indication for CT angiography
Mills, 2004
Mills et al. 2004 6 Core Curriculum V5
 Measuring the ABI
• The patient is placed supine

• Evaluate the pulses by palpation. Pulses may be considered normal, diminished (compared
with the contralateral limb), or absent.

• Next, a blood pressure cuff is placed proximal to the ankle of the injured limb.

• The systolic pressure is determined with a Doppler probe at either the posterior tibial artery or
the dorsalis pedis artery.

• The same measurement is performed on the ipsilateral uninjured upper extremity, measuring
the systolic pressure at the brachialis artery

• The ABI is obtained by dividing the pressure of the injured lower limb by the pressure of the
uninjured upper limb

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 Knee Dislocation

Reduce the Knee

Assess Pulses
Obtain ABI

Distal Pulses Present Distal pulses asymmetric Absent Distal Pulse

or or
ABI>0.90 Clear signs of limb ischemia
Distal pulses present with ABI<0.90
Admit for 24 hours
Close observation Arteriogram Emergent Surgical with
On-table arteriogram
Serial examinations

Nicandri et al, 2009 7

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Attention!!!
• Intimal tears of the popliteal artery may initially not be flow limiting.

• In case of high suspicion (altered ABIs), consider a CT angiography

• If non limiting flow intimal tear is confirmed by CT angiography: observe the

patient closely, keep vascular team aware, and do not use tourniquet at the
time of any reconstructive knee surgery.

• At admission, in cases of absent perfusion…

• Emergent surgical exploration
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Meta-analysis 862 patients

Incidence of vascular injury: 18% (171 patients)
80% of cases of vascular injuries required surgical repair
12% of cases with vascular injuries resulted in amputation
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Vascular injuries associated with dislocation of the knee.
Green NE, Allen BL. J Bone Joint Surg Am 1977;59:236–9.
9

 Amputation rate
 Surgery in the first 8 hours = 11%
 Surgery after 8 hs = 86%
Message:
Don’t delay a surgical exploration if there is no limb
perfusion after reducing a knee dislocation.
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 Neurological Assessment
 Incidence of Nerve Injury 4.5% – 40%
21% complete recover

29% partial recover

50% did not recover

 Surgical procedure: Neurolysis (most of the times performed

in association with posterolateral corner reconstruction)
Lachman JR et al., 2015 10
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Differentiate between complete and incomplete

nerve palsy determines the prognosis

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 Peroneal Nerve Injury in the Setting of Knee Dislocations

Physical Exam Physical Exam

Partial Nerve Palsy Complete Nerve Palsy

Observe Electromyography (EMG) Testing

Consider Later No motor action

Tendon Transfer potentials

Ultrasound Testing to Assess

Nerve continuity

1. Complete Nerve
Future meniscoligamentous Discontinuity
repair / reconstruction 2. Time from injury to possible
surgery is less than 3 months

O’Malley et al. 2016 11

Direct Nerve Transfer Core Curriculum V5
Cases that should be taken to the OR immediately:

•Irreducible knee dislocation

•Open knee dislocation
•Associated vascular injury – no perfusion to the limb
•Compartment syndrome

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 Irreducible Knee Dislocation
Dimple Sign
Skin depression on the medial side of the knee
Typical case of rotatory instability of the knee.

The medial femoral condyle buttonholes the medial capsule

and the medial collateral ligament (MCL) protrudes into the
knee joint.

This requires open reduction!!

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Open Knee Dislocation
• Urgent reduction of the knee at the ER

• Immediate neurovascular assessment (before and after

reduction)

• Urgent surgical management = open fractures

• Irrigation and Debridement

• Provisional stabilization: spanning fixator

• Image studies: radiographs/MRI

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Associated Vascular Injury
• At the time of the vascular repair:
• Knee should be reduced
• Knee should be spanned with an external fixator
• Fasciotomies may be considered pending on time
of ischemia, and characteristics of the soft tissues

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 Compartment Syndrome
• The knee should be reduced

• A provisional spanning external fixator secures the reduction

• Fasciotomies: the four compartments of the leg should be released

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 4
Knee dislocations:
Classification

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Timing
•Acute < 3 weeks

•Chronic > 3 weeks

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 Classification - Kennedy
Tibial position with respect to the femur
Anterior It is not applicable if the knee is reduced at patient’s admission.

Posterior Up to 80% of the knee dislocations reduce spontaneously before

patient’s admission.
Medial

Lateral It does not describe which structures have been torn

Rotatory
(Combination)

Kennedy et al, JBJS 1963 12 Core Curriculum V5

Anterior Knee Dislocation

50% of all knee dislocations

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If Hyperextension > 50 degrees…

Popliteal
Artery
Tear

Kennedy et al, JBJS 1963

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 Posterior Knee Dislocation
Mechanism: Dashboard

30% of all knee dislocations

Arterial injury possible due to the intimal tear

Non rare: Extensor mechanism disruption

Kennedy et al, JBJS 1963 12

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 Schenck Classification
Based on clinical evaluation under anesthesia
Supports the Decision Making

KD I: Either ACL or PCL are intact

KD II: Only ACL and PCL are torn
KD III: Both ACL and PCL and either Posterolateral (KD III L) or Posteromedial (KD III M)
KD IV: ACL + PCL + PMC + PLC
KD V: Association between articular fracture and knee dislocation

Schenck et al., Instr Courses Lectures 1999 13

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Decision making

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At patient’s admission…
• Reduce the joint

• Complete neurovascular evaluation

• Evaluation of the soft tissues: attention to open injuries and the “dimple sign”

• ABIs

• Knee radiographs

• Rule out emergent needs to a surgical trip to the OR

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 Closed reduction of knee dislocations
• Gentle manual traction

• Avoid pressure over the popliteal fossa

• Careful anterior translation of the bone located posteriorly

• Make sure to document the presence of pulses before and after reduction

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After close reducing the knee…
• … keep it reduced!

• Brace may be difficult in individuals with increased BMI or with

some degree of soft tissues compromise

• Spanning external fixator should be considered if the knee may not

stay stable with a brace.

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 Multiligament Knee Injury
Arterial Injury
NO Open Knee Dislocation YES

Inability to maintain
reduction YES

NO
Knee Brace/ Splint
NO Spanning
YES
Inability to Mobilize External Fixator
With Brace/Splint

NO Reconstructive Surgery

Rehabilitation
Clinical Follow-Up Levy et al., 2009 14
Postoperative Functional Questionaries Core Curriculum V5
Before definitive ligament reconstruction…
• Deep venous thrombosis (DVT) prophylaxis
• Low molecular weight heparin
• Should be administered from during the entire interval between spanning
external fixator and definitive reconstruction of the knee

• In case there is documented DVT

• A consideration should be given to an inferior vena cava filter placement
with chemical anticoagulation

Collins et al, 1992 15 ; Sems et al, 2009 16 ; Levy et al., 2010 14

Levy e al. 2010
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 Ligament Repair versus Reconstruction
Bone avulsions: Repair

PCL Avulsion
PCL Repair

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Mid-substance Tears
• Acute repair: peripheral structures (capsule, peel off injuries)
• Corners should be reinforced with reconstruction

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 Posterolateral Corner: Repair vs Reconstruction

17

Am J Sports Med: 33 (6), 2005

Failure rate of 9% (2/22) with reconstruction versus 37% (13/35) in repairs (p=.03)

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Posterolateral Corner: Repair vs Reconstruction

18
Am J Sports Med: 38 (4), 2010
45 PLC injuries, 17 excluded
28 knees with data
Repair in 10, 4 failures (40%)
Reconstruction in 18, 1 failure (6%)

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 Posterolateral Instability: When should you repair?

Avulsion of a large bone fragment from the

fibula – ORIF with screw and washer

If allograft is not available in your hospital

and you don’t have adequate autograft
available

If only repair, consider holding motion

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Posterolateral Corner: Anatomy

FCL

Popliteus

PFL
Popliteus

PFL
FCL

3 Key Structures:
Fibular Collateral Ligament
Popliteofibular Ligament
Popliteus Tendon Core Curriculum V5
Isometric versus Anatomic
• It is critical to determine where you anchor the
reconstruction in the femur to avoid a change in graft
length with flexion/extension
• Dror Paley

• Cadaveric study
Stannard et al, Determining the isometric point of the knee: a comparison of the radiographic and
anatomic techniques. J Knee Surg 2012 Mar 25(1): 71-4 19

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Isometric Point
Intersection between Blumensaat line and the projection of the posterior femoral cortical

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• Negative (shortening) measurements in red
• Significant difference between anatomic and
fluoro methods
• p = 0.000176
• Fluoro more accurate by more than 3 mm of
excursion
• Nine knees (47%) had excursion
> 4mm using the anatomic method

• One knee (5%) had excursion

> 4mm using the radiographic method

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• Graft passed through fibula, up to isometric point with suspensory fixation.

• Separate popliteus graft if needed

• Tighten FCL in 20 - 30° of flexion and neutral internal rotation

• Tighten popliteus in extension

• Reconstructs the posterolateral corner

• Stannard et. al. 2020 20

 21

In this biomechanical study, double bundle PCL reconstructions more closely

replicated the ex vivo biomechanical functions of the native ligament
immediately after implantation.

Double bundle suspensory fixation technique replicated most closely the native PCL.

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 J Bone Joint Surg Am. 2014;96:184-91 22

Level I Prospective study

Hinged knee brace versus hinged external fixation
Less failures with hinged external fixation

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Hinged External Fixator – For very unstable knees

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 Timing for Definitive Ligament Surgery
Conflicting literature

• Acute Repair/Reconstruction – Performed within the first three weeks of the injury
– when tissues are still identifiable without significant scarring;

• Staged Repair/Reconstruction – Consists in repairing/reconstructing the peripheral

ligaments followed by delayed cruciate ligament reconstructions once the range of
motion is restored;

• Delayed Reconstruction – Performed once the peripheral soft tissues have some
degree of healing, and the knee has complete range of motion

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 Critical aspects to be considered
• The PCL determines the reference knee axis of rotation

• The PCL reconstruction takes precedence over the ACL, as it will

determine a reference alignment between the tibia and the femur

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Case Example
•Female, 34yo
•Left Varus Knee Dislocation
•Peroneal Nerve Injury
•Posterolateral corner injury (Lateral Collateral + Biceps
Tendon)

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Type IV A

AM

Kfuri and Schatzker Core Curriculum V5

Posterolateral Corner Injury

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Fracture dislocation: widened tibial plateau Compromise of the anteromedial tibial rim
Lateral translation of the tibia Instability = Lack of containment
Instability = Lack of containment

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Reducing the tibial subluxation

Periarticular clamp applied to the

medial femoral epicondyle and to the
anterolateral tibial rim

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 Restoring the Tibial Containment

Anteromedial buttress Horizontal plate to buttress the rim

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6 months PO

No pain

Stable joint

0 to 120 degrees of flexion

Tibial plateau fixation +

Posterolateral corner repair

and reconstruction

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Take home messages

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Knee Dislocations
Easy to overlook!!

50% -80% of the cases are spontaneously reduced at hospital admission

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Knee Dislocations
Should be always suspected:

1. High energy polytrauma

2. Unexpected knee swelling, tenderness, effusion

3. High energy tibial plateau fractures

4. Polytrauma patients with hip dislocation (dashboard mechanism)

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Knee Dislocations
At admission:

1. Detailed, documented vascular assessment: pulses, perfusion, ABIs

2. Repeated vascular assessment every every four hours. Admit the patient!

3. Document the neurological status of the patient (sensation and motricity)

4. Reduce the knee as soon as possible if dislocated. Document pulses before and after!

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Knee Dislocations
Emergencies that should be taken to the Operation Room:

1. Vascular injury

2. Compartment syndrome

3. Open knee dislocation

4. Irreducible knee dislocation (lateral dislocation, medial dimple sign)

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Knee Dislocations
Once reduced:

1. Hinge knee brace if suitable

2. Spanning external fixator (very unstable knees, morbid obese patients, open injuries)

3. Hinge external fixator: in association with multiligament knee reconstruction, specially in

cases of vascular repair

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Knee Dislocations
Stage 2: Definitive ligament reconstruction

1. Three to four weeks after initial injury

2. Will be dictated by soft tissues envelope and overall patient’s clinical status

3. Posterior cruciate ligament is the critical structure to determine the proper relationship between tibia and

femur

4. Peripheral ligaments should be reconstructed and not only repaired

5. Anterior cruciate ligament may be performed in a staged manner, allowing for early motion after

reconstructing PCL and corners Core Curriculum V5

Knee Dislocations
Schenk V

1. Understand the complexity of the injury: MRI

2. In case of tibial plateau fractures: fix the fracture, examine the knee under anesthesia

3. Consider reconstructing the corners (especially the posterolateral corner in association

with a varus fracture dislocation - Kfuri/Schatzker types IV P or IV A)

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References
1. Rihn JA, Groff YJ, Harner CD, Cha PS. The acutely dislocated knee: evaluation and management. J Am Acad Orthop Surg. 2004 Sep-Oct;12(5):334-46.
2. Robertson A, Nutton RW, Keating JF. Dislocation of the knee. J Bone Joint Surg Br. 2006 Jun;88(6):706-11.
3. Natsuhara KM, Yeranosian MG, Cohen JR, Wang JC, McAllister DR, Petrigliano FA. What is the frequency of vascular injury after knee dislocation? Clin
Orthop Relat Res. 2014 Sep;472(9):2615-20.
4. 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. 2004 May;86(5):910-5.
5. Barnes CJ, Pietrobon R, Higgins LD. Does the pulse examination in patients with traumatic knee dislocation predict a surgical arterial injury? A meta-
analysis. J Trauma. 2002 Dec;53(6):1109-14.
6. 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.
2004 Jun;56(6):1261-5.
7. Nicandri GT, Chamberlain AM, Wahl CJ. Practical management of knee dislocations: a selective angiography protocol to detect limb-threatening
vascular injuries. Clin J Sport Med. 2009 Mar;19(2):125-9.
8. Medina O, Arom GA, Yeranosian MG, Petrigliano FA, McAllister DR. Vascular and nerve injury after knee dislocation: a systematic review. Clin Orthop
Relat Res. 2014 Sep;472(9):2621-9.

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References
9. Green NE, Allen BL. Vascular injuries associated with dislocation of the knee. J Bone Joint Surg Am. 1977 Mar;59(2):236-9.

10. Lachman JR, Rehman S, Pipitone PS. Traumatic Knee Dislocations: Evaluation, Management, and Surgical Treatment. Orthop Clin North Am. 2015 Oct;46(4):479-93.

11. O'Malley MP, Pareek A, Reardon P, Krych A, Stuart MJ, Levy BA. Treatment of Peroneal Nerve Injuries in the Multiligament Injured/Dislocated Knee. J Knee Surg. 2016
May;29(4):287-92.

12. Kennedy JC. Complete Dislocation of the Knee Joint. Journal of Bone & Joint Surgery. 1963 45(5): 889-904.

13. Schenck RC Jr, Hunter RE, Ostrum RF, Perry CR. Knee dislocations. Instr Course Lect. 1999;48:515-22.

14. Levy BA, Fanelli GC, Whelan DB, et al. Controversies in the treatment of knee dislocations and multiligament reconstruction. J Am Acad Orthop Surg 2009;17(4):197–
206.

15. Collins D, Barnes C, McCowan T, Nelson C, Carver D, McAndrew M, Ferris E (1992) Vena caval filter use in orthopaedic trauma patients with recognized preoperative
venous thromboembolic disease. J Orthop Trauma 6:135–138

16. Sems S, Levy B, Herrera D, Templeman D, Dajani K (2009) Incidence of Deep Venous Thrombosis After Temporary Joint Spanning External Fixation for Complex Lower
Extremity Injuries. J Trauma Injury Infect Crit Care 66:1164–1166

17. Stannard JP, Brown SL, Farris RC, McGwin G Jr, Volgas DA. The posterolateral corner of the knee: repair versus reconstruction. Am J Sports Med. 2005 Jun;33(6):881-8.

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References
18. Levy BA, Dajani KA, Morgan JA, Shah JP, Dahm DL, Stuart MJ. Repair versus reconstruction of the fibular collateral ligament and

posterolateral corner in the multiligament-injured knee. Am J Sports Med. 2005 Jun;33(6):881-8.

19. Stannard JP, Hammond A, Tunmire D, Clayton M, Johnson C, Moura C. Determining the isometric point of the knee. J Knee Surg.

2012 Mar;25(1):71-4.

20. Stannard JP, Stannard JT, Cook JL. Surgical treatment of ACL, PCL and Lateral Side Injuries. Sports Med Arthrosc Rev 2020;28:94–99

21. Nuelle CW, Milles JL, Pfeiffer FM, Stannard JP, Smith PA, Kfuri M Jr, Cook JL. Biomechanical Comparison of Five Posterior Cruciate

Ligament Reconstruction Techniques. J Knee Surg. 2017 Jul;30(6):523-531.

22. Stannard JP, Nuelle CW, McGwin G, Volgas DA. Hinged external fixation in the treatment of knee dislocations: a prospective

randomized study. J Bone Joint Surg Am. 2014 Feb 5;96(3):184-91.

23. Kfuri M, Schatzker J. Revisiting the Schatzker classification of tibial plateau fractures. Injury. 2018 Dec;49(12):2252-2263.

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Acknowledgment

The authors would like to thank Stacy Turpin Cheavens, MS, CMI, Certified
Medical Illustrator University of Missouri, Depart-ment of Orthopedic
Surgery for some of the illustrations included in this presentation.

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Thank you! University of Missouri, Columbia

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