Knee Dislocation - Orthopaedic Trauma - Lecture Slides, Slides for Orthopedics. Acharya Nagarjuna University
devaki21 December 2012

Knee Dislocation - Orthopaedic Trauma - Lecture Slides, Slides for Orthopedics. Acharya Nagarjuna University

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Knee Dislocation, Multiligamentous Injury, Ligament Structures, Patella Tendon, Anatomy Osseous, Anatomy Nerves, Cadaveric Knee Specimens, Avulsion Injuries of Cruciates are some points from this lecture. This lecture is...
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Knee Dislocation Boston Orthopaedic Trauma Symposium September 28, 2002

Knee Dislocation and Multiligamentous Injury


4 ligament structures ACL PCL MCL LCL & PLC (lateral side) Popliteus Biceps femoris Popliteofibular lig. ITB Capsule

Patella tendon

Anatomy: Osseous

Femoral condyles articulate with tibial plateau

Change in this relationship

defines dislocation


Popliteal a. vulnerable Tethered proximally by

adductor hiatus Tethered distally by soleus

arch Incidence of injury 20-35% Most common in ant./post.

dislocations (40% incidence) If popliteal artery disrupted

there is inadequate flow distally Geniculate aa. not sufficient

Anatomy: Nerves

Main issue: Peroneal nerve Posterior to Biceps femoris Tethered @ fibular neck Injured by Tension: varus injury Direct injury Aggressive varus EUA (?)

Pathomechanics: Mechanisms of Injury

Low energy Sports Morbidly obese patient

levering over planted foot

High energy Motor vehicle collisions Pedestrians struck by autos


Kennedy, 1963 10 cadaveric knee specimens Hyperextension ACL PCL Posterior capsule torn @ 30º

hyperextension Popliteal artery @ 50º hyperextension


Avulsion injuries of cruciates Clinical studies: Sisto (1985) & Frassica (1992) Combined data 80% PCL avulsion (“femoral peel off”) 30% ACL avulsion

Schenck (1999) Cadaveric cruciate injury model Hyperextension with variable strain (velocity) high (5400%/sec): stripping lesion femur low (100%/sec): mid-substance tear



Frassica 1992 Mayo Clinic 14 2 million admissions

Wascher 1997 New Mexico 33 5 years

Eastlack 1997 US Army 28 5 years

Moore 1990 Denver 0.12 % of all trauma admissions


True incidence is probably underreported Because 20% - 50% spontaneously reduced Depends on practice environment

Trauma center Sports medicine practice General orthopaedics

Determining True Incidence

Constitutes Dislocation: Presents dislocated Reduced bicruciate injury Dislocatable on EUA 4 ligs. out on MRI

Probably with 3 ligs out too (multi- directional instability in setting of MRI confirmed bicruciate injury)

Physical Examination

Inspection Obvious deformity?

Consider immediate reduction Hint: Coexistent varus/valgus instability in extension = ACL

and PCL injury

Hemarthrosis May be absent 2° to capsular disruption

Popliteal or med/lat ecchymosis Evaluate skin: open dislocation, fx blisters, puckering

c/w irreducible dislocation • ↑ Hyperextension

Physical Examination

Vascular Exam Dorsalis pedis and posterior tibial aa. Pulse absent

Consider immediate closed reduction If still absent O.R. for exploration If pulse returns consider angiogram vs. observation

8 hour ischemic time is MAXIMUM

Pulse present A.B.I. > 0.9 observe (serial exams), +/- arterial doppler A.B.I < 0.9 angiogram &/or exploration

Physical Examination

Neurologic Exam Peroneal Nerve

EHL &/or tibialis anterior strength Dorsal 1st web space sensation

Tibial Nerve FHL &/or gastroc/soleus strength Lateral border & plantar surface of foot


Physical Examination Isolated Ligament Exam ACL

Lachman @ 30° PCL

Posterior drawer @ 90° LCL/PLC

Varus stress @ 30° and full extension  ↑ Tibial E.R. @ 30°  ↑ Posterior tibial translation @ 30°

MCL Valgus stress @ 30°

Patellar tendon Palpable tendon, straight leg raise, maintain extension

Physical Examination

Combined Ligament Exam LCL/PLC & Cruciate

 ↑ Varus in full extension & 30°

MCL & Cruciate (PCL)  ↑ Valgus in full extension & 30°

PLC & PCL  ↑ Tibial E.R. @ 30° & 90°  ↑ Posterior tibial translation @ 30° & 90°

Stability in full extension Excludes significant PCL or capsular injury

Associated Injuries: Polytrauma

Knee dislocation is a spectrum of injuries Simple

Low energy sports related Commonly an isolated injury

Complex High energy vehicular trauma Associated extremity & multi-system injuries Peroneal n. /popliteal a. injury & sequella

Important differences Future functional activities Ability to participate in rehabilitation program Systemic and/or physiologic factors?

Imaging the Dislocated Knee

Plain X-ray




CT Scan Doppler

Plain Radiographs Views

AP & lateral 45° oblique Patellar sunrise (not if still dislocated)

Findings Obvious dislocation Asymmetric joint space, subluxation Fracture/dislocations Lateral capsular sign (Segond) Avulsions (tibial spine, medial

epicondyle, tibial PCL insertion) Proximal fibula fracture Osteochondral defects

MRI Indications: all knee dislocations and equivalents Valuable diagnostic tool Pre-operative planning

Identify ligament injury Partial vs. complete Midsubstance vs. @ origin or insertion E.g.: Injury location influences incision, surgery

Lateral structures: popliteus, LCL, biceps Associated meniscal pathology Displaced in notch early surgery MCL in joint or flipped on itself won’t heal

Articular cartilage lesions Helps determine treatment plan Timing, procedure, approaches

Potter et al. JOT 2002

Early Management of Knee Dislocations

Orthopedic Emergency!!! Assess Neurovascular Status Closed Reduction

“Dimple sign” = irreducible (posterolateral dislocation) Requires open reduction

If no pulse s/p reduction Vascular evaluation/exploration


Direction of Dislocation

Position of knee Direction of applied force Degree of force and and

angle of inappropriate motion incurred

Hyperextension ± varus/valgus anterior Flexion + posterior force



Purpose Determine prognosis (outcome) Communication Guide treatment

Historical: Kennedy (1963) Tibial position with respect to femur Visual inspection Radiographs

Positional Classification: Problems

20% - 50% reduced at presentation (unclassifiable)

Does not define exact status of ligaments Collateral: MCL vs. LCL-PLC Knee dislocation with intact PCL Myers (1975), Shelbourne (1992), Cooper (1992) ACL + collateral “simple treatment” Vascular injury less likely?

Knee dislocation with intact ACL Schenck (1992)

Fracture dislocation patterns: Moore (1981)

Classification: Structures Involved







Schenck 1992


arterial injury

nerve injury

fracture dislocation

Anatomic Classification of Knee Dislocations

I single cruciate + collateral ACL + collateral PCL + collateral

ACL / PCL collaterals intact

KDV is a variable bag of fx-dislocations

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