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Vol 8, No 2, March/April 2000
97
Injuries involving the posterolateral
structures of the knee are significantly
less common than those affecting the
medial or anterolateral structures,
but may result in greater degrees of
disability. The overall incidence of
acute posterolateral rotatory instabil-
ity (PLRI) has been reported to be
less than 2% of all acute ligamentous
knee injuries.
1
Because the complex
anatomy and biomechanics of the
posterolateral structures are not com-
pletely understood, PLRI of the knee
represents a challenging diagnostic
and therapeutic problem for the
orthopaedic surgeon.
Historically, PLRI has been de-
fined as the instability pattern that
results from an injury to the arcuate
ligament complex. It has been pos-
tulated that the lateral tibial plateau
externally rotates around the axis of
the intact posterior cruciate liga-
ment (PCL) and subluxates posteri-
orly in relation to the lateral fe-
moral condyle.
2

This concept of the
PCL as the center of rotation of the
knee has been challenged; it is now
believed that a coupled relationship
exists between the posterolateral
structures and the cruciate liga-
ments. As a result, a high incidence
of combined injury patterns is
observed clinically, including an-
terolateral and anteromedial insta-
bility in addition to PLRI. Hugh-
ston et al
2
observed that 12 of 28
patients (43%) with chronic PLRI
exhibited combined injury patterns.
Baker et al
3
observed a similar
trend in 10 (59%) of 17 patients, as
did DeLee et al
1
in 22 (65%) of 34
patients and Hughston and Jacob-
son
4
in 77 (80%) of 96 patients.
Thus, concurrent ligamentous in-
juries in other areas of the knee
should be suspected in cases of

acute and chronic PLRI.
Anatomy
There is a close structural relation-
ship among the structures of the
posterolateral corner of the knee.
Some studies have suggested that it
is impossible for an isolated popli-
teus tendon injury to occur without
associated weakening of other
components of the posterolateral
complex.
5
The overall functional
and clinical significance of these
interrelated structures is not yet
completely understood. Hughston
et al
2
defined the arcuate ligament
complex as the functional tendi-
nous and ligamentous complex
consisting of the lateral collateral
ligament (LCL), the arcuate liga-
ment, the popliteus muscle and
tendon, and the lateral head of the
gastrocnemius. These constituents
form a sling that functions stati-
cally and dynamically to control
rotation of the lateral tibiofemoral
articulation.

Dr. Chen is Chief Resident Physician,
Department of Orthopaedic Surgery, Hospital
for Joint Diseases, New York. Dr. Rokito is
Assistant Director, Sports Medicine Service,
Department of Orthopaedic Surgery, Hospital
for Joint Diseases. Dr. Pitman is Director,
Sports Medicine Service, Department of
Orthopaedic Surgery, Hospital for Joint
Diseases.
Reprint requests: Dr. Chen, Department of
Orthopaedic Surgery, Hospital for Joint
Diseases, 301 East 17th Street, New York, NY
10003.
Copyright 2000 by the American Academy of
Orthopaedic Surgeons.
Abstract
Isolated posterolateral rotatory instability of the knee is an uncommon injury
pattern that may result in significant degrees of functional disability. This in-
jury complex can be a challenging diagnostic and therapeutic problem for the
orthopaedic surgeon. The presence of associated ligamentous and soft-tissue
injuries, resulting in combined instability patterns, further complicates man-
agement. The results of recent research have enhanced our understanding of the
complex anatomy and biomechanics of the posterolateral aspect of the knee.
Numerous surgical techniques have been described for both repair and recon-
struction of the injured posterolateral structures; however, long-term functional
results have been only moderately successful.
J Am Acad Orthop Surg 2000;8:97-110
Acute and Chronic Posterolateral
Rotatory Instability of the Knee
Frank S. Chen, MD, Andrew S. Rokito, MD, and Mark I. Pitman, MD

Seebacher et al
6
developed a three-
layer concept of the posterolateral
structures (Fig. 1). Layer I, the most
superficial layer, consists of the ilio-
tibial band with its expansion ante-
riorly and the superficial portion of
the biceps femoris with its expansion
posteriorly. The peroneal nerve lies
deep and posterior to the biceps ten-
don at the level of the distal femur.
Layer II consists of the quadriceps
retinaculum anteriorly and the pa-
tellofemoral ligaments posteriorly.
The most important and deepest
layer, layer III, is composed of (1) the
lateral joint capsule and coronary
ligament, (2) the popliteus tendon,
(3) the LCL, and (4) the fabellofibular
and arcuate ligaments (Fig. 2). There
is significant anatomic variability
in the structures of this deepest layer.
The arcuate and fabellofibular liga-
ments are both present in approxi-
mately 67% of patients. The fabello-
fibular ligament is present alone in
20% of casesÑusually denoted by
radiographic evidence of a large fa-
bella. The arcuate ligament is pres-

ent alone in the remaining 13% of the
population, as suggested by the
absence of the fabella or its cartilagi-
nous remnant.
6
Iliotibial Band
The iliotibial band, which runs
between the supracondylar tubercle
on the femur and GerdyÕs tubercle
on the proximal tibia, is an impor-
tant stabilizer of the lateral com-
partment. The most important por-
tion of this structure acts as an
accessory anterolateral ligament.
7
During knee flexion, the iliotibial
band becomes tight and moves pos-
teriorly, exerting an external rota-
tional and backward force on the
lateral tibia. During knee exten-
sion, it moves anteriorly and is thus
spared in most cases of varus stress
and posterolateral injury.
Lateral Collateral Ligament
The LCL originates proximally
on the lateral femoral condyle and
inserts on the fibular head, rein-
forcing the posterior third of the
capsule. The LCL is the primary
static restraint to varus stress of the

knee.
1,8
In addition, the LCL also
provides resistance to external rota-
tion. Biomechanical studies have
shown that more than 750 N of
force is required to cause failure of
the LCL.
8
Isolated injuries to the
LCL are uncommon and usually oc-
cur in conjunction with injuries to
other ligamentous and soft-tissue
structures.
Popliteus
The obliquely oriented popli-
teus, which originates from the
posterior aspect of the tibia and
passes through a hiatus in the coro-
nary ligament to insert onto the lat-
eral femoral condyle, reinforces the
posterior third of the lateral cap-
sule and forms the lower part of
the floor of the popliteal fossa.
9
The popliteus also possesses at-
tachments to the lateral meniscus
in most of the population, poten-
tially contributing to the dynamic
stability of this structure. Electro-

myographic studies have shown
that the popliteus plays a major
role in both dynamic and static sta-
bilization of the lateral tibia on the
femur, including restriction of pos-
terior tibial translation, restriction
of external and varus rotation of
the tibia, and dynamic internal
rotation of the tibia.
Popliteofibular Ligament
The popliteofibular ligament
represents a direct static attachment
of the popliteus tendon from the
posterior aspect of the fibular head
to the anterior aspect of the lateral
femoral epicondyle.
9,10
It provides
a significant share of the overall
mechanical resistance to posterior
tibial translation, external rotation,
and varus rotation; a force of more
than 400 N is required to cause fail-
ure of this ligament.
8,10
In one
study,
10
it was present in 10 of 11
Posterolateral Rotatory Instability of the Knee

Journal of the American Academy of Orthopaedic Surgeons
98
Figure 1 Coronal section of the knee illustrates the three-layer concept of the anatomy of
the posterolateral structures, as described by Seebacher et al. (Adapted with permission
from Seebacher JR, Inglis AE, Marshall JL, Warren RF: The structure of the posterolateral
aspect of the knee. J Bone Joint Surg Am 1982;64:536-541.)
Prepatellar bursa (I)
Patellar retinaculum (II)
Iliotibial tract (I)
Lateral meniscus
Joint capsule (III)
Popliteus
tendon (III)
Popliteus
Fibular head
Arcuate
ligament
(III)
Ligament of
Wrisberg
Oblique
popliteus
ligament
LCL (III)
Fabellofibular
ligament (III)
Biceps tendon
Common
peroneal nerve
Patella

Fat pad
Anterior and posterior
cruciate ligaments
I - First layer
II - Second layer
III - Third layer
(91%) of cadaveric specimens de-
spite the overall variability noted in
the remainder of the posterolateral
complex. Many authors have stressed
the importance of this ligament in
maintaining posterolateral stability
and function.
Arcuate Ligament
Spanning the junction from the
fibular styloid process to the lateral
femoral condyle, the arcuate liga-
ment reinforces the posterolateral
capsule.
11,12
Possessing both a medi-
al and a lateral limb, this Y-shaped
ligament is composed of the lateral
portion of the popliteus tendon and
the fascial condensation over the
posterior surface of the popliteus
muscle. The fabellofibular, or short
collateral, ligament may also be pres-
ent in conjunction with the arcuate
ligament, providing a variable con-

tribution to overall posterolateral
stability.
6,12
Biceps Femoris
The biceps femorisÑconsisting
of a long and a short head with nu-
merous armsÑcourses posterior to
the iliotibial band and inserts pri-
marily on the fibular head. It also
sends strong attachments to the ilio-
tibial bands, GerdyÕs tubercle, the
LCL, and the posterolateral cap-
sule.
1,12
In conjunction with the ilio-
tibial band, the biceps femoris acts
as a powerful external rotator of the
tibia, as well as a strong dynamic
lateral stabilizer of the knee.
12
In-
jury to the biceps femoris complex
frequently occurs in PLRI.
Additional Structures
The middle third of the capsular
ligament blends with the capsule
over the LCL and inserts slightly
posterior to GerdyÕs tubercle.
11,12
Although this structure is most like-

ly a secondary restraint to varus
stress, DeLee et al
1
have reported a
33% incidence of injury to this liga-
ment in acute PLRI. The lateral
head of the gastrocnemius provides
varying degrees of posterolateral
stability and blends with the arcu-
ate ligament.
12
The lateral menis-
cus, which is stabilized by a portion
of the popliteus tendon as well as
the capsule, also contributes to lat-
eral stability by adding concavity to
the lateral tibial plateau.
12
The pos-
terior capsule is attached proximally
to the lateral femoral condyle and is
covered by the lateral gastrocne-
mius and plantaris. The distal cap-
sular attachment is complex; the
popliteus muscle and aponeurosis
blend into the tibial attachment lat-
eral to the PCL, whereas the distal
corner is stabilized to the fibula by
the arcuate, popliteofibular, and
fabellofibular ligaments.

12
Biomechanics
The lateral ligamentous structures
of the knee differ from the medial
structures in that the lateral struc-
tures are stronger and more sub-
stantial and are subjected to greater
forces during the normal gait cycle.
During the stance phase, the medial
compartment is under compression,
while the lateral structures are un-
der tension secondary to the relative
position of the normal mechanical
axis of the lower extremity, which
lies slightly medial to the center of
the knee.
The structures of the posterolat-
eral corner function primarily to
resist posterior translation as well
Frank S. Chen, MD, et al
Vol 8, No 2, March/April 2000
99
Plantaris muscle
Medial head of
gastrocnemius
muscle
Lateral head of
gastrocnemius
muscle
Fabella

Arcuate ligament
Fabellofibular ligament
Medial collateral ligament
Lateral inferior
geniculate artery
Popliteus muscle
Medial head of
gastrocnemius muscle
Lateral head of
gastrocnemius muscle
Semimembranosus
muscle
Femur
Patella
Prepatellar bursa
Patellar
retinaculum
Apex of
fibular head
Biceps tendon
Iliotibial tract
Common
peroneal nerve
Figure 2 Oblique view of the posterolateral aspect of the knee after removal of the two
superficial layers.
as external and varus rotation of the
tibia. The posterolateral structures,
however, act in concert with the
PCL in providing this overall stabil-
ity. The complex structure of the

knee does not allow for pure rota-
tional and translational motions;
consequently, abnormal pathome-
chanics usually result from a com-
bination of coupled rotation and
translation.
5,12
Cadaveric studies have been
conducted in which sectioning of
the posterolateral structures and
the PCL was performed to deter-
mine their individual effects on
various motions in the knee. The
findings of these studies will be
briefly summarized.
Anterior-Posterior Translation
Sectioning of the posterolateral
structures alone results in an in-
crease in posterior translation of the
lateral tibial plateau primarily at 30
degrees of flexion, with a minimal
increase at 90 degrees of flex-
ion.
5,13,14
However, when the pos-
terolateral structures and the PCL
are sectioned, increases in posterior
translation of both the medial and
the lateral tibial plateaus are ob-
served at both 30 and 90 degrees of

knee flexion.
13-15
Thus, the postero-
lateral structures appear to provide
resistance to posterior tibial transla-
tion primarily at lesser degrees
(e.g., 30 degrees) of flexion, whereas
the PCL provides secondary resis-
tance throughout a full range of
motion.
Varus-Valgus Rotation
Sectioning of the PCL alone does
not affect varus rotation of the tibia.
Isolated sectioning of the postero-
lateral complex, primarily the LCL,
results in increased varus rotation
from 0 to 30 degrees of flexion, with
the maximal increase observed at
30 degrees.
5,14,15
Combined section-
ing of the PCL and posterolateral
structures results in increased varus
rotation (as much as 19 degrees) of
the knee at all angles of flexion,
with the maximal increase observed
at 60 degrees.
14,15
Thus, the pos-
terolateral structures act as a re-

straint to varus rotation primarily
at lesser degrees of knee flexion
(maximal restraint at 30 degrees).
Internal-External Rotation
Isolated sectioning of the poste-
rolateral structures has been shown
to result in increased external rota-
tion of the lateral tibial plateau
when subjected to a posteriorly
directed force, with maximal exter-
nal rotation observed at 30 degrees
of flexion. Insignificant increases
in external rotation are observed at
90 degrees of flexion with an intact
PCL.
5,14,15
Combined sectioning of
the PCL and posterolateral struc-
tures results in an increase in exter-
nal rotation of the tibia on the
femur at all angles of knee flexion,
with the maximal increase (as
much as 20 degrees of external
rotation) noted at 90 degrees.
14,15
Thus, the posterolateral structures
appear to provide maximal re-
straint to tibial external rotation
primarily at lesser degrees of knee
flexion and also play an important

overall role in coupled tibial exter-
nal rotation in conjunction with the
PCL. It should be noted, however,
that isolated sectioning of the PCL
does not result in increased tibial
external rotation at any flexion
angle. Thus, in the presence of
clinically increased tibial external
rotation, an injury to the posterolat-
eral complex should be suspected.
Intra-articular Pressures
Sectioning of both the posterolat-
eral structures and the PCL results
in increased medial and lateral
compartment pressures, as well as
increased patellofemoral pressures
secondary to a Òreverse MaquetÓ
effect. These elevated compartment
pressures may predispose to the de-
velopment of early degenerative
joint disease.
16
Sectioning of the
LCL and posterolateral structures
has also been shown to result in
increased stresses on the anterior
cruciate ligament (ACL) with inter-
nal rotation, as well as on the PCL
with external rotation.
17

Mechanism of Injury
Most cases of PLRI are secondary
to trauma, with approximately 40%
occurring as a result of sports in-
juries. It has been suggested that
certain factors may predispose to
PLRI, such as genu varum, congen-
ital ligamentous laxity, and various
developmental factors (e.g., recur-
vatum, epiphyseal dysplasia).
12
The usual mechanism of injury
involves hyperextension with a
varus moment combined with a
twisting force. With the knee in
extension, the posterolateral cap-
sule is the principal restraint to
injury. A posterolaterally directed
blow to the medial tibia with the
knee in extension is the most com-
mon mechanism of injury.
12
This
results in forceful hyperextension
with simultaneous external rota-
tion of the knee. Much less com-
monly, these injuries occur due to
noncontact hyperextension and
external rotation. Sudden upper
leg and body deceleration with the

lower leg fixed may result in injury
to the posterolateral structures.
12
It
is important to note, however, that
all of these mechanisms can result
in injury to the cruciate ligaments
and other knee structures, account-
ing for the high incidence of com-
bined injury patterns.
Clinical Presentation
In cases of acute PLRI, patients usu-
ally describe a history of trauma and
present with pain over the posterolat-
eral aspect of the knee. Patients may
also report motor weakness as well
as numbness and paresthesias in the
Posterolateral Rotatory Instability of the Knee
Journal of the American Academy of Orthopaedic Surgeons
100
lower leg secondary to an associated
peroneal nerve palsy. This has been
reported to occur in as many as 30%
of patients with acute PLRI.
12
After the initial pain and swell-
ing of acute injuries have subsided,
patients may also report instability,
primarily with the knee in extension
(e.g., during toe-off), such that the

knee buckles into hyperexten-
sion.
12,15
This functional instability
is characteristic of patients with
chronic PLRI as well. Patients may
have difficulty in ascending and
descending stairs, as well as with
cutting activities requiring lateral
movement. In addition to their
functional knee instability, patients
with chronic PLRI may describe
pain localized along the lateral joint
line. Patients may also present with
gait abnormalities and may describe
symptoms secondary to associated
ligamentous injuries.
12,15
Physical Examination
Physical examination should in-
volve an overall inspection of the
limb, including gait pattern, limb
alignment, and mechanics. Pa-
tients typically exhibit gait abnor-
malities characterized by a varus
thrust at the knee coupled with
knee hyperextension in stance
phase.
12,15
Patients may require the

use of shoe lifts or high-heeled
shoes to maintain ankle equinus
and prevent knee hyperextension.
12
Patients often maintain the tibia in
internal rotation while ambulating
to prevent subluxation, as the knee
is more unstable in external rota-
tion. In addition, patients may
exhibit varus malalignment with
the mechanical axis shifted medially,
resulting in an increased adduction
moment of the knee that further
exacerbates their symptoms. This
overall varus alignment is an im-
portant factor that may lead to fail-
ure of operative treatment if not
corrected at the time of surgery.
Patients may present with an
abrasion or an area of ecchymosis
over the anteromedial tibia after
recent trauma. One should have a
high index of suspicion for knee
dislocations in cases of multiple lig-
amentous injuries. A careful neuro-
logic examination, focusing on the
peroneal nerves, should be per-
formed. In addition, there are
numerous specific tests that are
valuable in the diagnosis of sus-

pected PLRI. These individual tests
are most useful when used in con-
junction with clinical suspicion and
other physical examination find-
ings. Assessment of an awake pa-
tient may be difficult; in many
instances, especially with acute
injuries, examination under anes-
thesia may be helpful.
Anterior-Posterior Translation
In cases of isolated posterolateral
injury, patients will demonstrate
evidence of increased posterior tib-
ial translation on the femur only at
30 degrees of flexion. However, in
cases of combined posterolateral
and PCL injury, patients will have
increased posterior tibial translation
at both 30 and 90 degrees of flexion.
A quadriceps active test should
then be performed to further assess
the integrity of the PCL. This test is
performed by having the patient
actively contract the quadriceps
with the knee flexed 70 degrees and
the foot fixed. Anterior translation
of the tibia from its posteriorly sub-
luxated position is observed with
PCL deficiency.
Varus-Valgus Rotation

(Adduction Stress Test)
Combined LCL and posterolat-
eral injuries will result in increased
varus opening at both 0 and 30 de-
grees of flexion, with the maximal
increase at 30 degrees. With the
patient lying supine and the knee
flexed 20 to 30 degrees, a varus or
adduction force is then applied to
the leg with gentle internal rotation
of the tibia while supporting the
thigh. Opening of the lateral com-
partment is indicative of injury to
the posterolateral corner and corre-
lates with injury to the LCL and the
arcuate ligament.
18
A large degree
of varus laxity in full extension
may indicate combined injuries of
the posterolateral corner, the PCL,
and possibly the ACL as well.
External-Rotation Recurvatum
Test
This test is performed with the
patient supine (Fig. 3). The examiner
grasps the great toes of both feet
simultaneously and lifts the lower
limbs off the examining table. Posi-
tive findings indicative of postero-

lateral injury and instability include
hyperextension (recurvatum) of the
knee, external rotation of the tibia,
Frank S. Chen, MD, et al
Vol 8, No 2, March/April 2000
101
Figure 3 Demonstration of recurvatum
and relative tibia vara at the knee on the
external rotational recurvatum test suggests
posterolateral instability. (Adapted with
permission from Hughston JC, Norwood
LA Jr: The posterolateral drawer test and
external rotational recurvatum test for pos-
terolateral rotatory instability of the knee.
Clin Orthop 1980;147:82-87.)
and increased varus deformity of
the knee. The sensitivity of this test,
as reported in the literature, ranges
from 33% to 94%.
1,3
Posterolateral Drawer Test
This test is performed with the
patient supine with the hip flexed
45 degrees, the knee flexed 80 de-
grees, and the tibia in 15 degrees of
external rotation. With the foot fixed,
pressure is applied to the tibia in
a similar fashion to the posterior
drawer test. Lateral tibial external
rotation and posterior translation

relative to the lateral femoral con-
dyle are indicative of injury to the
posterolateral structures.
19
This test
is not specific for PLRI, and its diag-
nostic sensitivity is variable (report-
edly as high as 75%).
1,3
Tibial External Rotation Test
This test is performed at both 30
and 90 degrees of knee flexion with
the patient either prone or su-
pine.
15,20
The degree of external
rotation of the foot relative to the
axis of the femur is evaluated while
palpating the tibial plateau (Fig. 4).
In cases of PLRI, the lateral plateau
moves posteriorly. In anteromedial
rotatory instability, the medial
plateau moves anteriorly. A differ-
ence in external rotation of more
than 10 degrees between the nor-
mal and the affected side is consid-
ered evidence of a pathologic con-
dition. With isolated posterolateral
injury, an increase in external rota-
tion compared with the contralater-

al limb is noted only at 30 degrees;
an increase at both 30 and 90 de-
grees is indicative of a combined
posterolateral and PCL injury.
15,20
Posterolateral External
Rotation Test
This test is a combination of the
posterolateral drawer and external
rotation tests and is performed at
both 30 and 90 degrees of knee flex-
ion as a coupled force of posterior
translation and external rotation of
the tibia is applied (Fig. 5). Postero-
lateral subluxation of the lateral tib-
ial plateau only at 30 degrees is
indicative of isolated PLRI (corre-
lated with injuries to the LCL and
the lateral head of the gastrocne-
mius). Subluxation at both 30 and
90 degrees is indicative of com-
bined PLRI and PCL injury.
18
Reverse Pivot-Shift Test
With the patient lying supine, a
valgus stress is applied to the tibia
while bringing the knee from 90
degrees of flexion to full extension
with the foot in external rotation.
This test is positive for PLRI if there

is a palpable shift or jerk as the lat-
eral tibial plateau (which is sublux-
ated posteriorly in flexion) reduces
with extension.
18
This test is not
specific for PLRI; it has been reported
to be positive in 11% to 35% of nor-
mal, asymptomatic subjects.
12,21
Positive findings may be correlated
with generalized ligamentous laxity
and are significant only if the symp-
toms are reproduced.
Other Clinical Tests
Other diagnostic tests described
for the diagnosis of PLRI include
the dynamic posterior shift test and
the standing apprehension test.
The latter is performed with the
patient slightly flexing the knee
while bearing weight on the affected
leg. Increased internal rotation of
the lateral femoral condyle relative
to the fixed tibial plateau combined
with the subjective experience of
Ògiving wayÓ is considered to be
100% sensitive for the presence of
PLRI.
22

Radiologic Evaluation
Standard plain radiographs (ante-
roposterior and lateral views) of the
knee in cases of suspected injury to
the posterolateral complex may
show a proximal fibular tip avulsion
or occasionally a fibular head frac-
Posterolateral Rotatory Instability of the Knee
Journal of the American Academy of Orthopaedic Surgeons
102
Figure 4 The tibial external rotation test (supine). Excessive external tibial rotation as
well as posterior translation of the lateral tibial plateau is noted in cases of PLRI. (Adapted
with permission from Loomer RL: A test for knee posterolateral rotatory instability. Clin
Orthop 1991;264:235-238.)
ture.
1,12
Avulsion of GerdyÕs tuber-
cle may also be observed secondary
to iliotibial band injury.
12
This must
be distinguished from a Segond frac-
ture, which is indicative of lateral
capsular avulsion as a result of ACL
disruption. In cases of more severe
injury with associated ligamentous
disruption, additional findings, such
as tibial plateau fractures or even
knee dislocation, may be seen. In
cases of chronic PLRI, evidence of

patellofemoral or tibiofemoral de-
generative changes may be ob-
served. Most commonly, involve-
ment of the lateral compartment is
more advanced than that of any
other compartment. Lateral tibial
osteophytes may be seen, along with
evidence of lateral compartment
involvement, such as joint-space
narrowing and subchondral sclero-
sis of the tibial plateau.
Varus stress radiographs may be
helpful in determining the degree
of injury. A constant force is placed
on the knee in the frontal and sagit-
tal planes to demonstrate both the
direction and the degree of instabil-
ity. In addition, full-length weight-
bearing radiographs of both lower
extremities may be helpful in deter-
mining overall limb alignment, es-
pecially in cases of chronic PLRI.
Valgus osteotomies, if needed, can
then be planned and templated in
anticipation of correction of varus
limb alignment, along with surgical
reconstruction of the posterolateral
complex.
Magnetic resonance imaging is
an excellent diagnostic tool in the

evaluation of posterolateral injuries,
providing visualization of individ-
ual posterolateral structures. A
bone contusion on the anteromedial
femoral condyle indicative of pos-
terolateral injury is frequently ob-
served. Magnetic resonance imag-
ing is also useful for evaluation of
the cruciate ligaments and other lig-
amentous and soft-tissue structures
in the knee to determine the pres-
ence of associated injuries.
Treatment
The natural history of isolated
PLRI has not yet been clearly delin-
eated. The results of early studies
indicated that most professional
and recreational athletes who sus-
tain isolated posterolateral injury
have no evidence of impaired func-
tion initially.
3,12
However, it has
been postulated that there may be a
predisposition to early degenera-
tive joint disease. It is also believed
that there is an increased degree of
disability when a combined liga-
mentous injury pattern exists. The
role of early surgical intervention is

still unclear. However, surgical
repair or reconstruction of the pos-
terolateral structures should be
performed before degenerative
changes develop in the knee joint.
In general, nonoperative man-
agement should be prescribed for
patients with mild instability with-
out significant symptoms or func-
tional limitations. These patients
may be treated with a brief period
of initial immobilization (2 to 4
weeks), followed by an extensive
rehabilitation program that in-
cludes protected range-of-motion
and quadriceps-strengthening exer-
cises. Sport-specific drills may be
begun and gradually progressed as
strength increases. Baker et al
3
ob-
served that 14 of 31 patients with
mild instability were able to return
to their preinjury level of athletic
participation with nonoperative
treatment.
3
Currently, the indications for
surgical treatment of PLRI of the
knee include symptomatic instabil-

ity with functional limitations as
confirmed by significant objective
physical findings (e.g., 2+ or greater
varus opening at 30 degrees or a
positive external-rotation recurva-
tum, tibial external rotation, or pos-
terolateral external-rotation test).
In general, surgical repair is recom-
mended within the first 2 weeks, if
possible. Results of chronic PLRI
repair have been shown to be infer-
ior to those for acute PLRI. In addi-
tion, simultaneous evaluation and
treatment of associated ligamentous
injuries is mandatory. OÕBrien et
al
23
noted that the most common
Frank S. Chen, MD, et al
Vol 8, No 2, March/April 2000
103
Figure 5 The posterolateral external rotation test at 30 degrees. Left, Patient is supine
with the knee flexed at 30 degrees and in neutral rotation. Center, A coupled force of pos-
terior translation and external rotation is applied to the tibia while palpating the postero-
lateral aspect of the knee. Right, Abnormal posterolateral subluxation of the lateral tibial
plateau indicative of PLRI is shown by the arrow. (Adapted with permission from
LaPrade RF, Terry GC: Injuries to the posterolateral aspect of the knee: Association of
anatomic injury patterns with clinical instability. Am J Sports Med 1997;25:433-438.)
identifiable cause of ACL recon-
struction failures was unrecognized

and untreated concomitant PLRI.
In cases of combined injury pat-
terns, reconstruction of the ACL or
PCL should be performed either
prior to or concurrently with repair
or reconstruction of the posterolat-
eral structures.
In addition to addressing con-
comitant ligamentous injuries, it is
also important to correct any varus
knee alignment that may be pres-
ent. A valgus osteotomy of the
proximal tibia with distal advance-
ment of the iliotibial band with a
bone block can be performed.
24
This should be done either prior to
or at the time of surgical recon-
struction of the posterolateral struc-
tures. Uncorrected varus lower-
limb alignment may lead to failure
of the posterolateral reconstruction
secondary to chronic repetitive ten-
sile stresses and stretching of the
surgically reconstructed structures.
In general, the common goal of the
numerous surgical procedures
described is to restore stability of
the knee by resisting varus stress,
posterior tibial translation, and tib-

ial external rotation. Surgical op-
tions can be divided into four main
categories: primary repair, augmen-
tation, advancement, and recon-
struction.
Surgical Approach
Despite the numerous surgical
techniques described for posterolat-
eral repair and reconstruction, no
single universal surgical approach
has been adopted. In general, a lat-
eral skin incision is made with the
knee slightly flexed and is carried
from the midlateral aspect of the
distal thigh along the iliotibial band,
extending distally past GerdyÕs
tubercle. Terry and LaPrade
11
re-
cently described a surgical approach
consisting of three fascial incisions
along with a capsular incision for
exposure of the posterolateral struc-
tures. The first fascial incision
bisects the iliotibial band; the sec-
ond is made between the posterior
border of the iliotibial band and the
short head of the biceps femoris;
and the third is made along the pos-
terior border of the long head of the

biceps femoris. The capsular inci-
sion is made along the anterior bor-
der of the LCL.
Direct Primary Repair
Direct repair of the posterolateral
structures should be attempted ini-
tially if the tissues are of good quali-
ty, in order to restore both the ten-
sion in the popliteal complex and
the overall stability provided by the
posterolateral corner.
12,24-26
Primary
repair may be possible in many
acute cases, but in chronic cases in
which extensive scarring precludes
the definition of individual struc-
tures, direct repair is usually not
possible. Repair of the posterolat-
eral structures should be performed
with the knee in approximately 60
degrees of flexion and the tibia in
either neutral or slight internal rota-
tion.
12,25
Disruption of the tibial attach-
ment of the popliteus can be re-
paired by reattaching the popliteus
tendon by means of either sutures
or a cancellous screw to the postero-

lateral tibia
24,25
(Fig. 6). Avulsion of
the femoral insertion of the popli-
teus usually occurs along with avul-
sion of the femoral origin of the
LCL; these structures can be reat-
tached to an osseous bed in the lat-
eral femoral condyle by means of
sutures through transosseous drill
holes.
12,25
Disruption of the fibular
attachment of the popliteofibular
ligament can be addressed by teno-
desing the popliteus tendon to the
posterior aspect of the fibular head
and reinforcing it with the fabello-
fibular ligament (if present).
24,25
Avulsions of the LCL and the arcu-
ate ligament from the fibular styloid
process can also be repaired through
transosseous drill holes in the fibu-
lar head.
12
Augmentation of Posterolateral
Structures
Augmentation of the posterolat-
eral structures is recommended

when the popliteus and its related
structures are attenuated and the
quality of the primarily repaired tis-
sues is tenuous.
24,25
In this instance,
the tibial attachment of the popliteus
can be augmented with a strip of the
iliotibial band that is left attached
distally to GerdyÕs tubercle. The ilio-
tibial band strip is passed from ante-
rior to posterior through a drill hole
in the proximal tibia and then
sutured to the popliteus tendon
24,25
(Fig. 7, A). When the popliteofibular
ligament is disrupted and irrepa-
rable, a central slip of the biceps ten-
don can be utilized to augment and
reconstruct this structure. While
leaving its distal attachment to the
fibular head intact, the central slip of
the biceps is sutured to the posterior
Posterolateral Rotatory Instability of the Knee
Journal of the American Academy of Orthopaedic Surgeons
104
Figure 6 Direct repair of popliteus tendon
injury. Disruption of the tibial attachment
of the popliteus or the popliteus muscle-
tendon junction may be treated by tenode-

sis of the popliteus tendon to the posterolat-
eral aspect of the proximal tibia. (Adapted
with permission from Maynard MJ, Warren
RF: Surgical and reconstructive technique
for knee dislocations, in Jackson DW [ed]:
Reconstructive Knee Surgery. New York:
Raven Press, 1995, pp 161-183.)
fibula, passed under the remaining
biceps, and secured to the lateral
femur
24
(Fig. 7, B).
Advancement of Posterolateral
Structures
Arcuate complex advancement
has been recommended by numer-
ous authors for cases in which the
posterolateral structures are insuffi-
cient or incompetent for direct pri-
mary repair.
1,3,4,26,27
Advancement
of the posterolateral complex (i.e.,
LCL, popliteus muscle and tendon,
posterolateral capsule, arcuate liga-
ment, and lateral gastrocnemius
tendon) can be performed either
proximally or distally back to its
anatomic location on the femur or
tibia. In cases of chronic PLRI with

an LCL of normal integrity, proxi-
mal advancement of the posterolat-
eral structures can be performed if
the popliteofibular ligament is
intact. Superior and proximal
advancement of the posterolateral
complex is performed in line with
the LCL into a trough in the distal
femur (Fig. 8). Tensioning is per-
formed with the knee in 30 degrees
of flexion and neutral tibial rota-
tion. It has been suggested that
recession of the popliteus at the
femoral insertion will restore stabil-
ity and tension in the posterolateral
complex, but this technique alone is
ineffective in cases of injury to the
distal structures, such as the popli-
teofibular ligament.
12
Numerous authors have reported
good results with advancement of
the arcuate complex. DeLee et al
1
reported that 8 (73%) of 11 patients
with acute PLRI had good objective
and functional results at the 7.5-year
follow-up examination, with no evi-
dence of degenerative joint disease
and no revisions. Hughston and

Jacobson
4
reported that of 19 pa-
tients with isolated chronic PLRI
treated with proximal arcuate com-
plex advancement combined with
distal primary repair, 12 (63%) had
good functional results at 4 years.
Noyes and Barber-Westin
27
reported
on 21 patients with combined PLRI
and ACL or PCL injuries treated
with proximal advancement of the
posterolateral structures, noting
good functional results at 42 months
in 14 (67%), with a failure rate of 9%
(2 patients). The disadvantage of
proximal arcuate complex advance-
ment lies in the fact that the inser-
tion sites of the popliteus and LCL
are shifted anterior to the center of
knee rotation, which theoretically
may lead to stretching and eventual
failure of the repair over time.
Surgical Reconstruction
Reconstruction of the posterolat-
eral complex is performed in cases
of acute PLRI when the tissues are
Frank S. Chen, MD, et al

Vol 8, No 2, March/April 2000
105
Figure 7 A, Augmentation of the attenuated tibial attachment of the popliteus tendon can
be performed by using a portion of the iliotibial band passed from anterior to posterior
through a bone tunnel in the proximal tibia. (Adapted with permission from Maynard MJ,
Warren RF: Surgical and reconstructive technique for knee dislocations, in Jackson DW
[ed]: Reconstructive Knee Surgery. New York: Raven Press, 1995, pp 161-183.) B, A central
slip of the biceps is used to reconstruct the popliteofibular ligament. The central slip is
tubularized, sutured to the posterior fibula, and then passed under the biceps tendon and
subsequently secured to the lateral femoral condyle. (Adapted with permission from
Veltri DM, Warren RF: Operative treatment of posterolateral instability of the knee. Clin
Sports Med 1994;13:615-627.)
A B
Iliotibial graft
secured to
popliteus
tendon
Figure 8 Proximal arcuate complex
advancement. The structures of the pos-
terolateral region are advanced en bloc in
line with the LCL into a bone trough in the
lateral femoral condyle to restore tension in
the posterolateral complex. (Adapted with
permission from Hughston JC, Jacobson
KE: Chronic posterolateral rotatory insta-
bility of the knee. J Bone Joint Surg Am
1985;67:351-359.)
Popliteus
tendon
Lateral

capsular
ligament
Arcuate
ligament
complex
Fibular
collateral
ligament
Tendon of
lateral head of
gastrocnemius
irreparable or in symptomatic pa-
tients with chronic PLRI. In cases of
chronic PLRI with a deficient LCL,
graft reconstruction of both the LCL
and the surrounding posterolateral
structures is recommended. Recon-
struction of the LCL restores the pri-
mary restraint to varus stress and
replaces the tensile-bearing tissues
in the lateral aspect of the knee.
This can be performed by using
numerous techniques and grafts,
including Achilles tendon allograft
and patellar tendon autograft or
allograft.
17,24-31
A central slip of the
biceps tendon can also be used to
reconstruct the LCL; the distal inser-

tion of the biceps is left intact while
a central slip is tubularized, brought
proximally, and secured on the lat-
eral femoral condyle near the origin
of the LCL
24
(Fig. 9, A). Plication or
advancement of the residual pos-
terolateral structures to control ex-
ternal rotation can be performed if
the tissues are of sufficient quality.
Noyes and Barber-Westin
28
re-
ported significant subjective im-
provement in symptoms and func-
tion at the 42-month follow-up of
21 patients with chronic PLRI who
had been treated with LCL recon-
struction with use of an Achilles
tendon allograft combined with
either plication of the posterolateral
structures to the allograft or proxi-
mal advancement of these struc-
tures on the femur. Sixteen (76%)
patients had good to excellent func-
tional results. Failure of the recon-
struction occurred in only 2 pa-
tients (10%).
Clancy et al

29
have described bi-
ceps tenodesis for advancement
and tensioning of the posterolateral
structures. The entire biceps ten-
don is transferred anteriorly to the
lateral femoral epicondyle while
leaving the distal insertion intact
(Fig. 9, B). The proposed advan-
tages of this technique are that the
LCL is recreated while the arcuate
complex is tightened. In vitro ca-
daveric studies have shown that
biceps tenodesis at a fixation point
1 cm anterior to the LCL femoral
origin is effective in decreasing
external rotation and varus laxity at
up to 90 degrees of knee flexion.
30
Clancy et al
29
reported good func-
tional results in 90% of a small num-
ber of patients at 2-year follow-up,
including maintenance of stability
and return to preinjury level of ac-
tivity; no notable loss of hamstring
strength was observed. However, a
disadvantage of this technique is that
the popliteus and popliteofibular lig-

aments are not anatomically re-
produced. Because the biceps is
brought anterior to its normal func-
tional axis, the normal biomechanical
advantage and dynamic stabilizing
effect of this muscle are disrupted.
The tissue quality of the advanced
posterolateral structures may also
be tenuous. In vitro studies have
shown that tenodesis at a fixation
point other than 1 cm anterior to the
LCL femoral origin results in a Ònon-
isometricÓ graft position that does
not reduce external rotation or varus
stress at any degree of flexion.
30
Salvage posterolateral reconstruction
after a failed biceps tenodesis proce-
dure may be quite difficult.
In cases of chronic PLRI with a
deficient LCL in which the postero-
lateral structures are insufficient
for advancement, primary recon-
struction of the entire LCL and pos-
terolateral complex is necessary.
An Achilles tendon allograft, patel-
lar tendon autograft or allograft, or
free semitendinosus autograft
passed through a tibial tunnel just
below GerdyÕs tubercle and a tun-

nel in the lateral femoral condyle
can be used to reconstruct the
popliteus.
29
This, however, does
Posterolateral Rotatory Instability of the Knee
Journal of the American Academy of Orthopaedic Surgeons
106
Figure 9 A, Reconstruction of the LCL utilizing a central slip of the biceps tendon, which
is tubularized (as shown) and then secured proximally on the lateral femoral condyle
while leaving the remainder of the biceps attachment intact. (Adapted with permission
from Veltri DM, Warren RF: Operative treatment of posterolateral instability of the knee.
Clin Sports Med 1994;13:615-627.) B, Biceps tenodesis. The entire biceps tendon is trans-
ferred anteriorly and secured to the lateral femoral condyle, thereby recreating the LCL
and restoring tension to the residual posterolateral structures. (Adapted with permission
from Clancy WG, Meister K, Craythorne CB: Posterolateral corner collateral ligament
reconstruction, in Jackson DW [ed]: Reconstructive Knee Surgery. New York: Raven Press,
1995, pp 143-159.)
A B
Biceps
tendon
not recreate the popliteofibular lig-
ament.
Veltri and Warren
24
have de-
scribed a posterolateral reconstruc-
tion technique involving the use of
a patellar tendon autograft/allo-
graft or an Achilles tendon allo-

graft in which both the tibial and
fibular attachments of the popliteus
are addressed. The bone plug is
fixed proximally within a tunnel in
the lateral femoral condyle. The
graft is then split distally, passed
into both the tibial and the fibular
tunnels, and secured in neutral rota-
tion (Fig. 10, A). As a result, both
the tibial attachment of the popli-
teus and the fibular attachment of
the popliteofibular ligament are
reconstructed, which theoretically
reapproximates the normal anato-
my, biomechanics, and stability of
the posterolateral complex. The
LCL can also be concomitantly
reconstructed with a central slip of
the biceps tendon
24,25
(Fig. 10, B).
Albright and Brown
17
have de-
scribed a posterolateral corner re-
construction procedure in which an
extracapsular sling is created with
use of either an iliotibial band or an
Achilles tendon allograft/autograft.
The graft is secured to the proximal

tibia and is then brought from ante-
rior to posterior via a tibial tunnel to
exit anterior to the lateral head of the
gastrocnemius and the popliteus ten-
don. The posterior limb of the graft
is then passed up and secured to an
isometric point on the distal femur
just slightly superior and anterior to
the origin of the LCL (Fig. 11). At
follow-up evaluation an average of 4
years after the posterolateral sling
procedure was performed on 30
patients (29 of whom had associated
injury patterns in addition to PLRI),
26 patients (87%) reported improve-
ments in quality of life and objec-
tively demonstrated elimination of
the reverse pivot shift, varus laxity,
and knee hyperextension. All three
elite athletes in the study group were
able to return to full competition.
Frank S. Chen, MD, et al
Vol 8, No 2, March/April 2000
107
Figure 11 The posterolateral corner-sling reconstruction procedure. The graft is first
fixed to the proximal tibia and is then passed through a tibial tunnel from anterior to pos-
terior. The posterior limb is then brought up and secured to an isometric point on the lat-
eral femoral condyle. (Adapted with permission from Albright JP, Brown AW:
Management of chronic posterolateral rotatory instability of the knee: Surgical technique
for the posterolateral corner sling procedure. Instr Course Lect 1998;47:369-378.)

Hamstring
Femur
Quadriceps
Popliteus tendon
Iliotibial band
allograft
(posterior limb)
Iliotibial band
allograft
(posterior limb)
ACL
Medial
collateral
ligament
Medial
meniscus
Tibial tunnel
Tibial tunnel
Calf muscles
Figure 10 A, A split patellar tendon graft is used to reconstruct both the tibial and the
fibular attachments of the popliteus. The graft is first placed into the femoral tunnel and
then split. One end is secured in the tibial tunnel, and the other end is secured in the fibu-
lar tunnel. B, In addition to reconstruction of the popliteus and popliteofibular ligaments
with a split patellar tendon graft, the LCL is reconstructed by using a central slip of the
biceps tendon. (Adapted with permission from Veltri DM, Warren RF: Operative treat-
ment of posterolateral instability of the knee. Clin Sports Med 1994;13:615-627.)
A B
Latimer et al
31
have reported

good results with reconstruction of
the LCL and the posterolateral
complex by using a boneÐpatellar
tendonÐbone allograft secured with
interference screws. Fixation tun-
nels are placed distally in the fibu-
lar head and proximally at an iso-
metric point on the lateral femoral
condyle approximately 5 mm ante-
rior to the epicondyle and the
femoral origin of the LCL (Fig. 12).
The graft is passed under the ilio-
tibial band and is tensioned as a
valgus force is applied to the knee
in approximately 20 to 30 degrees
of flexion. The large cross-sectional
area of this graft restores the LCL
as well as potentially the arcuate
and popliteofibular ligaments, the
origins and insertions of which are
in close proximity to those of the
LCL.
31
At an average follow-up of
28 months, subjective instability
was eliminated in all 10 patients
with combined cruciate and pos-
terolateral instability, all of whom
underwent cruciate ligament re-
construction. No patient had more

than 5 mm of varus opening or 5
degrees of external rotation at 30
degrees of flexion compared with
the contralateral knee. Five pa-
tients returned to their preinjury
level of activity, and another 4
returned to activities that were
only one level lower than their pre-
injury level.
31
Surgical Complications
Complications as a result of surgi-
cal repair or reconstruction of the
posterolateral complex include (1)
common peroneal nerve palsy (the
incidence of which may be decreased
by careful dissection and protection
of the nerve at the time of surgery,
especially in cases of chronic PLRI);
(2) failure of the surgical reconstruc-
tion with persistent symptoms and
instability; (3) knee stiffness with
development of arthrofibrosis, which
may potentially require manipula-
tion and/or open release of intra-
articular adhesions; (4) hamstring
weakness (especially in biceps teno-
desis procedures); (5) infection; and
(6) irritation from hardware.
Postoperative

Rehabilitation
The postoperative rehabilitation pro-
tocol is dependent on the status of
concomitant ligamentous injuries
and/or reconstruction. Initially, it
involves protection of the operative
repair or reconstruction with the use
of a postoperative hinged knee
brace. Patients are maintained in
protected weight-bearing status
with the brace locked in extension
for the first 3 weeks. Isometric
quadriceps exercises are begun early
in the postoperative course, along
with range-of-motion exercises.
Active knee extension and resis-
tive closed-chain kinetic exercises in
a protected range of motion are
gradually progressed over the first
4 to 8 weeks. Patients should be
protected from external rotation
and varus stresses at the tibia for at
least 6 to 8 weeks. No hamstring
exercises are allowed until at least
12 weeks postoperatively to de-
crease external rotational torque
and posterior subluxation forces at
the knee joint. A functional knee
brace is usually worn as the activity
level is progressively increased.

Standard cruciate ligament rehabili-
tation protocols should be followed
concurrently in cases of concomi-
tant ACL or PCL reconstruction.
Posterolateral Rotatory Instability of the Knee
Journal of the American Academy of Orthopaedic Surgeons
108
Iliotibial
band
(split)
Interference
screws
Pin through
lateral condyle
Allograft
Figure 12 BoneÐpatellar tendonÐbone allograft reconstruction of the LCL. After fixation
of the distal bone plug in the fibular tunnel, the graft is routed under the iliotibial band. A
Beath pin is placed at an isometric point on the lateral femoral condyle approximately 5
mm anterior to the epicondyle and is then passed through medially. The graft is advanced
through the femoral tunnel, and the proximal bone plug is secured with use of an interfer-
ence screw. (Adapted with permission from Latimer HA, Tibone JE, ElAttrache NS,
McMahon PJ: Reconstruction of the lateral collateral ligament of the knee with patellar
tendon allograft: Report of a new technique in combined ligament injuries. Am J Sports
Med 1998;26:656-662.)
A well-structured and well-
supervised course of rehabilitation
lasting 9 to 12 months is usually
necessary. Most severe injuries
result in inability to return to vigor-
ous competitive sports, especially in

cases in which associated ligamen-
tous injuries require surgical recon-
struction.
Summary
Injuries to the posterolateral region
of the knee present a challenging
diagnostic and therapeutic problem
for the orthopaedic surgeon. Poste-
rolateral rotatory instability of the
knee is a complex condition that
can be quite disabling. It is neces-
sary to concurrently diagnose and
treat all other associated ligamen-
tous injuriesÑespecially those to
the ACL and PCLÑwhen injury to
the posterolateral complex is sus-
pected. A careful physical exami-
nation, including gait analysis and
overall limb alignment, should be
performed in addition to specific
tests evaluating the stability of the
posterolateral structures. Early
diagnosis and treatment in cases of
PLRI appear to result in better over-
all functional results.
The complex anatomy and biome-
chanics of the posterolateral structures
are not yet completely understood.
There is no universally accepted treat-
ment algorithm for either acute or

chronic PLRI. The surgical techniques
devised to reconstruct the posterolat-
eral structures and restore stability
have had only modest success. Fur-
ther clinical outcome studies are need-
ed to determine the long-term efficacy
of these various reconstructive proce-
dures. With greater understanding of
the posterolateral structures of the
knee, surgical techniques with better
functional long-term results can be
developed in the future.
Frank S. Chen, MD, et al
Vol 8, No 2, March/April 2000
109
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