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Posterolateral Rotatory Instability of the Knee
Steven A. Seeker, M.D.
ObjectivesDefine posterolateral rotatory instability
of the kneeEvolution of the human kneeAnatomy and biomechanics of the
posterolateral cornerClinical presentation and treatment
options for acute and chronic instability of the posterolateral corner of the knee
DefinitionHughston et al. JBJS 1976Posterior subluxation of the lateral tibial
plateau that can occur with an external rotation torque in knees with pathologic laxity of the posterolateral corner
Symptoms can occur acutely after violent injury or develop insidiously after relatively mild injury
Evolution of human knee Complex anatomy due
to evolution Early on, both the tibia
and fibula articulated with the femur
As the human knee evolved, the fibula and attached capsule moved distally
Evolution of human knee The popliteus
attachment moved from the fibular head to the femur creating an intra-articular portion
Biceps attachment moved from the capsule and tibia to the fibula
Posterolateral corner
“ Dark side of the knee “Andrews 1988
Varying anatomy and inconsistent terminology of the popliteofibular ligament
Anatomy of the posterolateral corner
Three distinct layers
Anatomy of the posterolateral corner
First layer Iliotibial tract
attaching to the tibia at Gerdy’s tubercle
Biceps femoris attaching to the fibular head
Second layer Quadriceps
retinaculum anteriorly
Patellofemoral and patellomeniscal ligaments posteriorly
Third layer Superficial lamina:
Lateral collateral ligament
Fabellofibular ligament
Third layer Superficial lamina:
Lateral collateral ligament
Fabellofibular ligament
Third layer Deep lamina:
Coronary ligament and popliteal hiatus
Popliteus
Arcuate ligament
Popliteofibular ligament
Oblique popliteal ligament
Third layer Deep lamina:
Coronary ligament and popliteal hiatus
Arcuate ligament
Popliteofibular ligament
Oblique popliteal ligament
Variable anatomySeebacher et al. JBJS 198235 cadaver kneesConclusions:
arcuate ligament alone in 13%fabellofibular ligament alone in 20%both in 67%no mention of popliteofibular ligament
Variable anatomySudasna and Harnsiriwattanagit 1990Dissection of fifty cadaver kneesConclusions:
“Fibular origin of the popliteus” (Popliteofibular ligament) in 98%Fabellofibular ligament in 68%Arcuate ligament in 24%
Variable anatomyWatanabe et al. arthroscopy 1993115 cadaver dissectionsConclusions:
lateral collateral and popliteus present in all knees“popliteus muscle with origin from the fibular head” (popliteofibular ligament) present in 94% of knees
Popliteofibular ligament (PFL)
Oversight in anatomy texts resulted in disappearance of this structure until only recently
Maynard et al. Am J Sports Med 1996 reported on the “rediscovery of the PFL”
Popliteofibular ligament (PFL)
This appears to be an important static stabilizer of the posterolateral corner
Popliteofibular ligament (PFL)
Maynard et al. Am J Sports Med 1996Cross sectional area of PFL only slightly
less than FCLMaximal force to failure PFL (425 N)
FCL (747 N)
Popliteofibular ligament (PFL)Veltri et al. Am J Sports Med 1996
PFL and popliteus were important in resisting posterior translation, primary varus rotation, and external rotation
Blood supply
Popliteal artery
Genicular arteries
Review of anatomy
Three layers of the posterolateral corner
First layer are dynamic stabilizers
Second layer relatively unimportant
Review of anatomyThird layer: static stabilizers and most
important layerFCL and popliteus are always presentPFL present in majority of kneesarcuate and fabellofibular ligaments are variablecoronary ligaments are very loose to allow for very mobile lateral meniscus
Biomechanics
Biomechanics Nielson et al. Arch Orthop Trauma Surg
1984, 1985 Lateral collateral and posterolateral capsule
resist varus and external rotation of the tibia Popliteus resists varus from 0-900 and resists
external rotation from 20-1300 of flexion PLC also is a secondary restraint to posterior
translation, but isolated sectioning of the PCL does not affect varus or external rotation
Biomechanics Gollehon et al. JBJS 1987 PCL resists posterior translation Sectioning of PLC/FCL causes the greatest
increase in varus and external rotation at 30o of flexion
Additional sectioning of PCL causes greater increase in varus and external rotation
ACL/PLC sectioning causes tibial internal rotation and anterior translation to be increased at 30o and 60o
ACL or PLC sectioning alone does not increase tibial internal rotation
BiomechanicsMarkolf et al. JBJS 1993
Sectioning of PLC significantly increases the force on the PCL between 45o and 90o of flexion
Sectioning of PLC increases mean force on ACL at all flexion angles
BiomechanicsNoyes et al. Am J Sports Med 1993Sectioning PLC increases lateral tibial
plateau posterior translation at 30o but not at 90o
Sectioning of PLC and PCL increases posterior subluxation of both plateaus at both 30o and 90o
BiomechanicsLaPrade et al. Am J Sports Med 1999Forces in ACL grafts when the
posterolateral corner had been sectioned were increased with coupled varus and external rotation at 0o and 30o
of flexion
BiomechanicsSkyhar et al. JBJS 1993Ten cadaver kneesCombined sectioning of PLC and PCL
resulted in significantly more patellofemoral contact force than sectioning of the PCL alone
BiomechanicsSummary: Isolated PCL tear does not increase
primary varus or external rotation Isolated FCL tear causes a mild
increase in varus angulation which is greatest at 30o of flexion
Injury of PLC with intact PCL results in maximal increase of varus, external rotation and posterior translation at 30o of flexion
BiomechanicsSummary:However, at 90o, the PCL fibers become
tight and exert a secondary constraint on varus and external rotation
PCL and PLC complete injury cause increased varus, external rotation and posterior translation at all flexion angles
Cruciate ligament grafts are at increased risk of failure in knees with posterolateral rotatory instability
Examination of the posterolateral corner
History and physical examspecial tests
Radiographic evaluationMagnetic resonance imagingArthroscopic evaluation
HistoryPain in posterolateral kneePeroneal nerve symptoms?May have medial or lateral joint line pain Instability with knee in extension
Physical examinationEdema, ecchymosis, induration and
tendernessFull ligament exam and neurovascular
exam in all patientsMay have standing varus alignment or a
varus thrust with walking May walk a flexed knee due to pain and
instability with knee hyperextension
Special testsPosterior drawerTibial external rotation (dial) testPosterolateral external rotation testReverse pivot shift testExternal rotation recurvatum test
Posterior drawer Performed at 30o and
90o
Laxity at 30o indicates PLC injury
Laxity at 90o indicates PCL injury
May appear like an ACL injury, but tibia is posterior and ACL endpoint is good
Tibial external rotation (dial) test
Performed while prone at 30o and 90o
PLC only:increased at 30o only
PCL only: no side to side difference
PCL and PLC: increased at 30o and 90o
Posterolateral external rotation test
Performed at 30o and 90o with coupled posterior and external rotation force
Similar results to drawer and dial tests
Reverse pivot shift test Sensation of
reduction when the flexed, externally rotated tibiaknee is extended with a valgus applied force
May be positive in up to 35% of normal knees during EUA
May be PLC or PCL injury
External rotation recurvatum test
Elevation of lower extremity by great toe results in hyperextension, varus and external rotation
PCL vs. PLC vs. Both
Radiographic evaluation Plain film
radiographs may show avulsion fractures, widened lateral joint lineSegond fracture (lateral capsular sign may be present)
Magnetic resonance imaging Yu et al. Radiology
1996 T2 weighted coronal
oblique MRI give best resolution of PLC
LaPrade et al. Am J Sports Med 2000
Developed protocol for PLC imaging
Arthroscopy Valuable to evaluate
popliteus and meniscus, as well as articular surface injuries prior to open repair
“Drive through sign” Caution:
fluid extravasation
Grading of injuryGrade 1: no abnormal motion with 0 –
5mm of joint opening, and definite end point
Grade 2: slight to moderate abnormal joint motion with 6 – 10 mm joint opening, and definite end point
Grade 3: markedly abnormal joint motion with greater than 10 mm joint opening, and no endpoint
Grading of injuryKannus Am J Sports Med 198923 patients with grade 2 and 3 injuries
treated non-operatively8 year follow-up11 patients with grade 2 lesions
excellent or good knee scores, 9 were asymptomatic, all had residual laxity, no DJD
12 patients with grade 3 lesions fair or poor knee scores, but not all isolated PLC injury, DJD in 6 patients
TreatmentNon-operative treatmentOperative treatment
1. Acute injury2. Chronic instability
Non-operative treatment Isolated posterolateral corner injuries
are treated with a hinged knee brace to prevent varus and external rotation
The literature supports non-operative management of all grade 1 and 2 isolated PLC injuries
However, may consider operative management of grade 2 lesion if cruciate reconstruction is planned
Operative treatmentAcute injury:
Direct repair within 3 weeks to avoid “matted mess” has best outcome+/- augmentation
Chronic instability:Reconstruction
Surgical approach
Incision
Surgical approach
Internervous plane: between ITB and BF
May osteotomize Gerdy’s tubercle for better visualization
Must see the common peroneal nerve
Direct repair
Skin incision often is the only dissection needed in acute injuries
Repair deep structures first, followed by superficial structures
Direct repair
May need to augment structures with autograft or allograft if structures are not repairable
Combination of techniques used to repair all structures
Order of evaluation / repairCoronary ligament: evaluate for tears or
avulsion from tibia – fix with sutures or anchors
Popliteus and popliteofibular ligaments: fix with anchors or pull-out sutures if avulsed or Kessler sutures if torn
FCL: sutures or anchorsArcuate and fabellofibular ligaments:
variable, but should be repaired if torn or avulsed
Reconstruction of chronic instability
Often needed after grade 3 injuries treated non-operatively
Surgical dissection more difficult secondary to scar
Goals: restore function and stability to the knee
Special considerations for reconstruction
Alignment: full length x-rays of lower extremity to evaluate
Varus with lateral thrust: HTO prior to reconstruction of posterolateral structures or repair will stretch out
High tibial osteotomy
Not like HTO for DJD
Long lateral incision centered over ITB
Gerdy’s tubercle advanced with bone plug
Avoid disruption of proximal tib-fib joint, as this will worsen PLC symptoms
High tibial osteotomy Gerdy’s fixed with
6.5mm screw Osteotomy fixed
with staples Fibular osteotomy
should be performed at the mid fibula level
Reassess PLC at 6 months, symptoms may resolve with re-alignment
High tibial osteotomyAlternatively, a medial opening wedge
osteotomy of the proximal tibia can be performed
Advantages: avoids the proximal tib / fib joint and posterolateral structures
Disadvantages: 2 surfaces to heal+/- use of allograft or ICBG
Posterolateral corner reconstruction
Advancement of femoral attachment of FCL and PTHughston and Jacobson
Advancement of FCL / popliteus and lateral gastroc origin with suturing of FCL to gastroc
96 knees follow-up 4 years85% objectively good78% subjectively good80% functionally good
Advancement of femoral attachment of FCL and PTHughston and Jacobson
Advancement fixed with knee at 90o
Criticized because it does not address PFL or popliteus musculotendinous junction
Advancement of femoral attachment of FCL and PTHughston and Jacobson
Knee is placed in a controlled motion brace with 45 degree extension block
Flexion is encouraged to prevent patellofemoral problems
Biceps tenodesis (Clancy and Sutherland)
Anchor the biceps to the lateral femoral condyle to reduce the deforming force in external rotation and to recreate the FCL
39 patients, average follow-up of 32 months77% no ADL restriction54% return to sports
Biceps tenodesis (Clancy and Sutherland)
Wascher Am J Sports Med 1993 biomechanical study showed that this was effective, but it overconstrained the joint
Veltri et al. Am J Sports Med 1996this does not address the popliteus or PFL
Biceps tenodesis (Clancy and Sutherland)
Many authors have been reluctant to attempt this because of the difficulty in salvaging the knee if this fails
Recession of PT and FCL (Jakob and Warner)
When the popliteus and FCL are stretched, but intact, the femoral attachment may be recessed and fixed by a screw / washer
Advantage is isometric placement
Recession of PT and FCL (Jakob and Warner)
If the PFL is intact, this procedure should tighten this structure as well
Posterolateral corner sling(Albright and Brown)
Uses autograft or allograft to recreate the static effect of the popliteus
Central third of the ITB is harvested and left attached to Gerdy’s tubercle
Tunnel drilled through lateral tibia to the point of normal popliteus passage on the posterior lateral plateau
Posterolateral corner sling(Albright and Brown)
Graft is fixed just proximal to the origin of the FCL
30 patients 8 excellent (no joint pathology)10 poor (joint pathology or instability)6 additional procedures
Does not address PFL or FCL
Anatomic reconstruction of PT and/or PFL and/or FCL
(Veltri and Warren) Suggested anatomic
reconstruction of all injured / attenuated structures
Popliteus: reconstruct with allograft (achilles) similar to Albright’s procedurefix with suture and buttons or interference screws
Anatomic reconstruction of PT and/or PFL and/or FCL
(Veltri and Warren) Popliteofibular ligament:
similar, but tunnel drilled through fibula to recreate origin of PFL ligamentfixed to lateral epicondyle just proximal to FCL originsecured with buttons or interference screws
Anatomic reconstruction of PT and/or PFL and/or FCL
(Veltri and Warren) Popliteus and PFL:
combine both reconstructions with a single split achilles allograft with bone end of the graft secured to the femur
Anatomic reconstruction of PT and/or PFL and/or FCL
(Veltri and Warren) Popliteus, PFL and
FCL: If FCL also requires reconstruction, use distally based segment of the biceps femoris with fixation to the epicondyle with screw and soft tissue washer
Anatomic reconstruction of PT and/or PFL and/or FCL
(Veltri and Warren) Patient is placed in
a hinged knee brace to prevent varus and external rotation
Toe touch weight-bearing with brace locked in extension
Allowed motion when NWB
Anatomic reconstruction of PT and/or PFL and/or FCL
(Veltri and Warren) Bike at 4 weeks Closed chain at 6
weeks Jogging at 4 months Brace worn for 6
months Return to sports at
6-9 months
Anatomic reconstruction of PT and/or PFL and/or FCL
(Veltri and Warren) This technique is
relatively new and there are no long term follow-up studies
Promising because of anatomic reconstruction of injured structures
Order of repair of the multiply ligamentously injured knee
Most authors at the recent AAOS suggested fixing the PLC prior to ACL or PCL repair
If all three are injured, fix the PLC first at 300, followed by the PCL
ACL may be fixed at a later date
Review of Posterolateral corner
Anatomy is variable, but the FCL, popliteus and popliteofibular ligaments are present in most knees
Careful physical examination of all ligaments will allow the diagnosis of injury to the PLC
PLC laxity is greatest at 30o of knee flexion
Arthroscopy and MRI are useful adjuncts to physical exam
Review of Posterolateral corner
Grade 1 and 2 isolated lesions can be treated conservatively
Grade 3 lesions should be treated operatively
Early operative intervention has the best chance of a good result
Late reconstruction is a salvage procedure
Prognosis is related to other related pathology (ie. DJD, meniscus tear, etc.)
Review of Posterolateral corner
Multiple methods of reconstruction are available
Anatomic reconstruction is a promising new method of reconstruction, but follow-up studies are not yet available