Updated: 2/14/2023

Knee Dislocation

0%
Topic
Review Topic
0
0
0%
0%
Flashcards
71
N/A
N/A
Questions
18
0
0
0%
0%
Evidence
51
0
0
0%
0%
Videos / Pods
12
0%
0%
Cases
7
Topic
Images
https://upload.orthobullets.com/topic/1043/images/Xray - Lat - knee dislocation (emedicine)_moved.jpg
https://upload.orthobullets.com/topic/1043/images/Clinical photo - recurvatum (emedicine)_moved.jpg
https://upload.orthobullets.com/topic/1043/images/MRI - coronal - knee dislocation (emedicine)_moved.jpg
  • Summary
    • Knee dislocations are high energy traumatic injuries characterized by a high rate of neurovascular injury.
    • Diagnosis is made clinically with careful assessment of limb neurovascular status. Radiographs should be obtained to document reduction. 
    • Treatment is generally emergent reduction and stabilization with assessment of limb perfusion followed by delayed ligamentous reconstruction. 
  • Epidemiology
    • Incidence
      • rare
        • 0.02% of orthopedic injuries
        • likely underreported as approximately 50% self-reduce and are misdiagnosed
    • Demographics
      • 4:1 male to female ratio
    • Location
      • tibiofemoral articulation (knee joint)
    • Risk factors
      • morbid obesity is a risk factor for "ultra-low energy" knee dislocations with activities of daily living
  • Pathophysiology
    • Mechanism of injury
      • high-energy vs low energy
        • high energy is usually from MVC, crush injury, fall from a height, or dashboard injury resulting in axial load to a flexed knee
        • low energy may be from an athletic injury or routine walking
      • hyperextension injury leads to anterior dislocations
      • posteriorly directed force across the proximal tibia (dashboard injuries) leads to posterior dislocations
    • Associated injuries
      • vascular injury
      • nerve injury
        • usually common peroneal nerve injury (25% incidence)
        • tibial nerve injury is less common
      • fractures
        • present in 60% of dislocations
      • soft tissue injuries
        • patellar tendon rupture
        • periarticular avulsion
        • displaced menisci
  • Anatomy
    • Osteology
      • the knee is a ginglymoid joint and consists of tibiofemoral, patellofemoral and tibiofibular articulations
    • Ligaments
      • PCL, ACL, LCL, MCL, and PLC are all at risk for injury
      • main stabilizers of the knee given the limited stability afforded by the bony articulations
    • Blood supply
      • popliteal artery injuries occur often due to tethering at the popliteal fossa
        • proximal - fibrous tunnel at the adductor hiatus
        • distal - fibrous tunnel at soleus muscle
      • geniculate arteries may provide collateral flow and palpable pulses masking a limb-threatening vascular injury
    • Biomechanics
      • the normal range of motion of 0-140 degrees with 8-12 degrees of rotation during flexion/extension
  • Classification
    • Descriptive
      • Kennedy classification based on the direction of displacement of the tibia
      • Kennedy classification 
        (based on the direction of displacement of the tibia)
      • Anterior (30-50%)
      • most common
        due to hyperextension injury
      •  usually involves tear of PCL
      •  an arterial injury is generally an intimal tear due to traction
      • the highest rate of peroneal nerve injury
      • Posterior (30-40%)
      •  2nd most common
      •  due to axial load to the flexed knee (dashboard injury)
      • the highest rate of vascular injury based on Kennedy classification
         has highest incidence of a complete tear of the popliteal artery
      • Lateral (13%)
      •  due to a varus or valgus force
      •  usually involves tears of both ACL and PCL
      • Medial (3%)
      •  varus or valgus force
      •  usually disrupted PLC and PCL
      • Rotational (4%)
      •  usually irreducible
      •  posterolateral is most common rotational dislocation
      •  buttonholing of femoral condyle through the capsule
    • Schenck Classification
      • based on a pattern of multiligamentous injury of knee dislocation (KD)
      • Schenck Classification
        (based on the number of ruptured ligaments)
      • KD I
      • Multiligamentous injury with the involvement of the ACL or PCL
      • KD II
      • Injury to ACL and PCL only (2 ligaments)
      • KD III
      • Injury to ACL, PCL, and PMC or PLC (3 ligaments).
        KDIIIM (ACL, PCL, MCL) and KDIIIL (ACL, PCL, PLC, LCL).
      • KD IV
      • Injury to ACL, PCL, PMC, and PLC (4 ligaments)
        Has the highest rate of vascular injury (5-15%%) 
      • KD V
      • Multiligamentous injury with periarticular fracture
  • Presentation
    • Symptoms
      • history of trauma and deformity of the knee
      • knee pain & instability
    • Physical exam
      • appearance
        • no obvious deformity
          • 50% spontaneously reduce before arrival to ED
          • may present with subtle signs of trauma (swelling, effusion, abrasions, ecchymosis)
        • obvious deformity
          • reduce immediately, especially if absent pulses
          • "dimple sign" - buttonholing of medial femoral condyle through the medial capsule
            • indicative of an irreducible posterolateral dislocation
            • a contraindication to closed reduction due to risks of skin necrosis
      • vascular exam
        • priority is to rule out vascular injury on exam both before and after reduction
          • serial examinations are mandatory
          • palpate the dorsalis pedis and posterior tibial pulses on injured and contralateral side
        • if pulses are present and normal
          • does not indicate the absence of arterial injury
            • collateral circulation can mask a complete popliteal artery occlusion
          • measure Ankle-Brachial Index (ABI) on all patients with suspected KD
            • if ABI >0.9
              • then monitor with serial examination (100% Negative Predictive Value)
            • if ABI <0.9
              • perform an arterial duplex ultrasound or CT angiography
              • if arterial injury confirmed then consult vascular surgery
        • If pulses are absent or diminished
          • confirm that the knee joint is reduced or perform immediate reduction and reassessment
          • immediate surgical exploration if pulses are still absent following reduction
            • ischemia time >8 hours has amputation rates as high as 86%
          • imaging contraindicated if it will delay surgical revascularization
          • if pulses present after reduction then measure ABI then consider observation vs. angiography
      • neurologic exam
        • assess sensory and motor function of peroneal and tibial nerve as nerve deficits often occur concomitantly with vascular injuries
      • stability
        • diagnosis based on instability on physical exam (radiographs and gross appearance may be normal)
        • may see recurvatum when held in extension
        • assess ACL, PCL, MCL, LCL, and PLC
  • Imaging
    • Radiographs
      • recommended views
        • pre-reduction AP and lateral of the knee
          • may be normal if spontaneous reduction
            • look for asymmetric or irregular joint space
            • look for avulsion fxs (Segond sign - lateral tibial condyle avulsion fx)
            • osteochondral defects
        • post reduction AP and lateral of the knee
      • optional views
        • 45-degree oblique if fracture suspected
    • CT
      • indications
        • fracture identified on post reduction plain films
        • obtain post reduction CT for characterization of fracture
      • findings
        • tibial eminence, tibial tubercle, and tibial plateau fractures may be seen
    • MRI
      • indications
        • obtain MRI after acute reduction but prior to hardware placement
        • required to evaluate soft tissue injury (ligaments, meniscus) and for surgical planning
  • Treatment
    • Nonoperative
      • emergent closed reduction followed by vascular assessment/consult
        • indications
          • considered an orthopedic emergency
        • vascular consult indicated if
          • pulses are absent or diminished following reduction
          • if arterial injury confirmed by arterial duplex ultrasound or CT angiography
      • immobilization as definitive management
        • indications (rare)
          • successful closed reduction without vacular compromise
          • most cases require some form of surgical stabilization following reduction
        • outcomes
          • worse outcomes are seen with nonoperative management
          • prolonged immobilization will lead to loss of ROM with persistent instability
    • Operative
      • open reduction
        • indications
          • irreducible knee
          • posterolateral dislocation
          • open fracture-dislocation
          • obesity (may be difficult to obtain closed)
          • vascular injury
      • external fixation
        • indications
          • vascular repair (takes precedence)
          • open fracture-dislocation
          • compartment syndrome
          • obese (if difficult to maintain reduction)
          • polytrauma patient
      • delayed ligamentous reconstruction/repair
        • indications
          • instability will require some kind of ligamentous repair or fixation
          • patients can be placed in a knee immobilizer until treated operatively
            • improved outcomes with early treatment (within 3 weeks)
  • Technique
    • Closed reduction
      • approach
        • anterior dislocation - traction and anterior translation of the femur
        • posterior dislocation - traction, extension, and anterior translation of the tibia
        • medial/lateral - traction and medial or lateral translation
        • rotatory - axial limb traction and rotation in the opposite direction of deformity
      • splinting
        • 20 to 30 degrees of flexion
    • Open reduction
      • approach
        • midline incision with a medial parapatellar arthrotomy
      • soft tissue
        • the medial capsule may need to be pulled over medial condyle if buttonholed
        • acute associated soft tissue injuries (patellar tendon rupture, periarticular avulsion, or displaced menisci) may benefit from acute repair
      • bone work
        • periarticular fractures may be fixed acutely or spanned with external fixator depending on surgeon preference
      • instrumentation
        • place knee-spanning external fixator in 20-30 degrees of flexion with knee reduced in AP and sagittal planes
    • Early ligamentous reconstruction (<3 weeks)
      • approach
        • arthroscopic versus open
          • arthroscopic may not be possible if large capsular injury and creates a risk of fluid extravasation and compartment syndrome
          • PLC and PMC require open reconstruction given subcutaneous nature and proximity to neurovascular structures
      • soft tissue work
        • arthroscopic reconstruction of ACL and/or PCL
        • address intraarticular pathology (menisci, cartilage defects, capsular injury)
        • open repair versus reconstruction of collateral ligaments
      • outcomes
        • acute (< 3 weeks) and staged reconstruction have equivalent outcomes
  • Complications
    • Vascular compromise
      • incidence
        • 5-15% in all dislocations
        • 40-50% in anterior or posterior dislocations
      • risk factors
        • KD IV injuries have the highest rate of vascular injuries
      • treatment
        • emergent vascular repair and prophylactic fasciotomies
    • Stiffness (arthrofibrosis)
      • incidence
        • most common complication (38%)
      • risk factors
        • more common with delayed mobilization
      • treatment
        • avoid stiffness with early motion
        • arthroscopic lysis of adhesion
        • manipulation under anesthesia
    • Laxity and instability
      • incidence
        • 37% of some instability, however, redislocation is uncommon
      • treatment
        • bracing
        • revision reconstruction
    • Peroneal nerve injury
      • incidence
        • 25% occurrence of a peroneal nerve injury
        • 50% recover partially
      • risk factors
        • anterior dislocations
      • treatment
        • AFO to prevent equinus contracture
        • neurolysis or exploration at the time of reconstruction
        • nerve repair or reconstruction or tendon transfers if chronic nerve palsy persists
        • dynamic tendon transfer involves transferring the posterior tibial tendon (PTT) to the foot
  • Prognosis
    • Complications frequent and rarely does knee return to a pre-injury state
Flashcards (71)
Cards
1 of 71
Questions (18)
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK

(SBQ20TR.4) A 37-year-old geocentric athlete presents to the trauma bay after a fall while free solo rock climbing. Upon presentation, he is complaining of isolated right knee pain and deformity. After appropriate ATLS stabilization, he is found to have the injury depicted in Figure A. Successful closed reduction is performed by the orthopedic resident on duty. What is the best next step in evaluating this patient for a vascular injury and what result would warrant concern for vascular injury?

QID: 215736
FIGURES:

Ankle systolic blood pressure/Brachial systolic blood pressure; 0.8

83%

(551/660)

Ankle systolic blood pressure/Brachial systolic blood pressure; 0.9

6%

(41/660)

Ankle diastolic blood pressure/Brachial diastolic blood pressure; 0.8

7%

(43/660)

Ankle diastolic blood pressure/Brachial diastolic blood pressure; 0.9

1%

(5/660)

Brachial systolic blood pressure/Ankle systolic blood pressure; 0.8

2%

(12/660)

N/A E

Select Answer to see Preferred Response

(OBQ20.141) A 22-year-old college student sustains a twisting injury to his knee while walking down a wet flight of concrete stairs. He is unable to bear weight and is taken to the local trauma center by emergency medical services. Radiographs obtained in the trauma bay are shown in Figures A and B. He is closed reduced under conscious sedation, and post-reduction radiographs demonstrate a congruent joint. He is sent for an MRI of his knee, and follows up in your clinic the next week. Which of the following is true regarding the definitive treatment of his injuries in an acute (< 3 weeks from time of injury) fashion?

QID: 215552
FIGURES:

Acute treatment is associated with lower rates of residual knee instability when compared to staged or chronic treatment

18%

(148/843)

Acute treatment is associated with the highest rates of good to excellent subjective outcomes

26%

(221/843)

Acute treatment is inferior to definitive nonoperative management

2%

(19/843)

Aggressive postoperative range of motion is associated with increased joint instability following acute treatment

5%

(43/843)

Patients managed acutely are more likely to have postoperative stiffness recalcitrant to intervention

48%

(403/843)

L 1 E

Select Answer to see Preferred Response

(OBQ19.114) A 26-year-old male presents to the emergency department with complaints of knee pain. He is a gymnast and states that just prior to arrival he sustained a twisting injury to the knee while landing on a trampoline. Figure A is the radiograph that was obtained in the emergency department. An attempt at reduction in the emergency department is unsuccessful. Which of the following clinical images would be expected in this scenario?

QID: 214016
FIGURES:

Figure B

89%

(1201/1357)

Figure C

2%

(28/1357)

Figure D

5%

(70/1357)

Figure E

1%

(10/1357)

Figure F

3%

(43/1357)

L 1 A

Select Answer to see Preferred Response

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK

(OBQ13.216) A 32-year-old professional skydiver lands awkwardly during a jump. He presents to the emergency room with bilateral knee injuries. Following successful closed reduction of both extremities, both feet are warm and pulses are present. Bedside doppler assessment is performed and the results are seen in Figure A. What would be the most appropriate next step in treatment?

QID: 4851
FIGURES:

Long-leg splinting of bilateral lower extremities, monitoring of bilateral pedal pulses for 48 hours

15%

(453/2967)

Intravenous dextran administration, repeat doppler evaluation at 6 hourly intervals

1%

(28/2967)

Perform CT angiography for bilateral lower extremities

14%

(424/2967)

Perform CT angiography for the left lower extremity, monitor right pedal pulses for 48 hours

68%

(2029/2967)

Surgical exploration of bilateral lower extremities

0%

(8/2967)

L 2 B

Select Answer to see Preferred Response

(OBQ13.128) A 30-year-old man is the front seat passenger in a motor vehicle accident. He presents with deformity in his knee seen in Figures A and B. Radiographs are seen in Figures C and D. Examination reveals weak foot pulses. After unsuccessful attempts at closed reduction, it is noted that the pulses are no longer palpable and the foot is cool. What is the next step in treatment?

QID: 4763
FIGURES:

Open reduction through an anteromedial approach, spanning external fixation. If pulses do not return, perform popliteal artery exploration.

70%

(3948/5667)

Closed reduction in the operating room using a femoral distractor. If pulses do not return, perform on-table angiogram.

14%

(778/5667)

Manual in-line skeletal traction using a calcaneal pin in the emergency room, provisional long-leg splinting. If pulses do not return, perform computed tomography angiography in the radiology suite.

3%

(168/5667)

Manual in-line skeletal traction using a proximal tibial pin in the emergency room, provisional long-leg splinting. If pulses do not return, perform standard angiography in the angiography suite.

4%

(207/5667)

Open reduction through a posterior approach, spanning external fixation. If pulses do not return, perform popliteal artery exploration.

9%

(532/5667)

L 3 B

Select Answer to see Preferred Response

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK

(SBQ12TR.5) Figures A and B are radiographs of a 20-year old male athlete that sustained a high impact tackle during a football game. What percentage of these injuries will present with an associated vascular injury?

QID: 3920
FIGURES:

10%

4%

(202/5125)

20%

17%

(887/5125)

40%

59%

(3024/5125)

70%

15%

(767/5125)

90%

4%

(222/5125)

L 2 C

Select Answer to see Preferred Response

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Evidence (51)
VIDEOS & PODCASTS (14)
CASES (7)
EXPERT COMMENTS (61)
Private Note