This document discusses posterolateral corner injuries of the knee. It provides details on the anatomy, mechanisms of injury, clinical evaluation, imaging, and treatment of these injuries. Key points include: - The posterolateral corner is made up of several static and dynamic stabilizers including the LCL, popliteus tendon, popliteofibular ligament, and biceps femoris tendon. - Injuries can range from grade I sprains to grade III complete ligament disruptions and are often associated with injuries to other knee ligaments. - Evaluation involves assessing varus and rotational stability along with imaging like MRI to identify injured structures. - Treatment ranges from bracing and rehabilitation for

1. POSTEROLATERAL
CORNER INJURY KNEE
DR MURUGESH KURANI MAHADEV
M.B.B.S., M. S. Ortho
Fellow In Arthroscopy And Sports Medicine
Fellow In Shoulder Surgery And Sports Trauma

2. TRAUMATIC KNEE INJURUES
ASSOCIATED WITH LATERAL KNEE INSTABILITIES AND CONCOMITANT LIG INJURIES (PCL>ACL)

3. EPIDEMIOLOGY
INCIDENCE:
APP. 7-16% OF KNEE LIG INJURIES
ONLY 28% OF ALL PLC INJURIES ARE ISOLATED
COMBINED CRUCIATE LIG INJURY (PCL>ACL)
MISSED PLC DIAGNOSIS IS 2nd MOST COMM CAUSE OF ACL RECON FAILURE

4. ETIOLOGY
BLOW TO ANTEROMEDIAL KNEE
VARUS BLOW TO FLEXED KNEE
CONTACT AND NONCONTACT HYPEREXTENSION KNEE INJURIES
ER TWISTING INJURIES
KNEE DISLOCATION

5. ASSOCIATED INJURIES
COMMON PERONEAL NERVE INJURIES (15-29%)
VASCULAR INJURIES

6. ANATOMY
STATIC AND DYNAMIC STABILISERS

7. STATIC STABILISER
MAJOR – 3
LATERAL COLLATERAL LIG (LCL) – PRIMARY VARUS
STABILISER OF KNEE
POPLITEUS TENDON (PLT)
POPLITEOFIBULAR LIGAMENT

8. OTHER STATIC STABILISERS
MENISCOFEMORAL AND MENISCOTIBIAL LIGAMENTS
ARCUATE LIGAMENT
FABELLOFIBULAR LIGAMENT

9. DYNAMIC STABILISERS
BICEPS FEMORIS
POPLITEUS MUSCLE
ILIOTIBIAL BAND (ITB)
LAT HEAD OF GASTROCNEMIUS

10. LCL/FCLATTACHMENTS :
FEMUR - In a shallow depression 1.4 mm
proximal and 3.1 mm posterior to the lateral
epicondyle (LE).
FIBULA - Approximately midway along the
lateral fibular head, in a small depression within
the biceps femoris bursa, 28.4 mm distal to the tip
of the styloid.
Average length : 70 mm
FUNCTION:
Primary static restraint to varus gapping of the knee
and also resist external rotation, particularly during
extension.
Secondary stabilizer against internal rotation and
anterior tibial translation.
THE CENTER OF THE FEMORAL ATTACHMENT IS 18.5 MM POSTERIOR TO THE FEMORAL ATTACHMENT OF THE
POPLITEUS TENDON.

11. PLT ATTACHMENTS:
FEMUR: Originates as tendon and has a relatively broad
footprint (0.59 cm2 ) located just posterior to the margin
of the lateral femoral condyle articular cartilage. This
attachment is found at the anterior fifth and proximal half
of the popliteal sulcus.
TIBIA: Posteromedial surface of tibia as fan shaped
muscle just above the soleal line
COURSE: The tendon courses posterodistally and passes
through the popliteal hiatus, where the tendon anchors to
the lateral meniscus with three popliteomeniscal fascicles.
The average length of the PLT is 54.9 mm, passing deep to the FCL.
FUNCTION:
primary static constraint against external rotation of
the tibia relative to the femur.
Secondary role in stabilizing against internal rotation,
varus gapping, and anterior tibial translation.

12. PFLATTACHMENTS:
Two divisions
FEMUR - Originate at the musculotendinous junction of the
popliteus muscle and insert distally and medially on the down
sloping portion of the fibular styloid process.
FIBULA - The larger posterior division (5.8 mm width) inserts
1.6 mm distal to the styloid process tip; the smaller anterior
division (2.6 mm width) inserts more distally, 2.8 mm distal to
the styloid tip.
FUNCTION:
Primary static restraint against external rotation.
Secondary stabilizer against varus rotation.

13. SEVERAL OTHER STRUCTURES ACT TO AUGMENT THE RESTRAINTS
ON KNEE MOTION
THE DISTAL ILIOTIBIAL BAND (ITB) - also plays
a role in posterolateral stability, connecting the iliac
crest of the pelvis to the patella, Gerdy’s tubercle, and
the PLC.
The distal ITB gives rise to the deep capsulo-osseous
layer which has attachments to the lateral head of the
gastrocnemius muscle, the biceps femoris, and the tibia
posterior to Gerdy’s tubercle.
FABELLOFIBULAR LIGAMENT - distal thickening
of the capsular arm of the short head of the biceps
femoris that extends vertically from the fabella to the
fibular styloid.
THE LATERAL GASTROCNEMIUS TENDON - attaches
to the bony or cartilaginous fabella before continuing
superiorly to insert on a supracondylar process on the
posterior femur, 13.8 mm posterior to the proximal FCL and
28.4 mm from the PLT attachment, just superior to the joint
capsule.
FABELLA found within the proximal lateral
gastrocnemius tendon in 30% of individuals.

14. THE ANTEROLATERAL LIGAMENT (ALL) - a thickening
within the “mid-third lateral capsular ligament,” has an
oblique course superficial to the FCL.
ORIGIN - Lateral femoral condyle just anterior to and
blending with the popliteus tendon.
INSERTION - Lateral meniscus and lateral tibial plateau,
typically about 5 mm distal to the joint line.
FUNCTION:
Serves as a restraint against internal tibial rotation at 30° of
flexion. While not technically a part of the PLC, the ALL
provides an important contribution to rotatory stability of the
lateral side of the knee.
THE PROXIMAL TIBIOFIBULAR JOINT (PTFJ)
LIGAMENTS - also contribute to the stability of the PLC,
connecting the medial proximal fibular head to the lateral
tibia.
THE MENISCOFEMORAL AND MENISCOTIBIAL
LIGAMENTS - connects the lateral meniscus to the tibia
at its posterior aspect, providing additional stability to the
posterolateral joint capsule.

15. The long head of the BFT divides into a direct and
anterior arm and several fascial components. The direct
arm inserts lateral to the fibular styloid; the anterior arm
separates 1 cm proximal to the fibular head and inserts
lateral to the fibular FCL attachment. The biceps bursa
fills the space between these arms and encloses the
distal FCL attachment, forming a convenient surgical
landmark.
The short head of the BFT also divides into an anterior
arm (attaches 1 cm posterior to Gerdy’s tubercle) and a
thicker direct arm, which inserts between the styloid
and the FCL insertion. The short head of the BFT has
numerous other connections to the capsulo-osseous ITB
layer, posterolateral joint capsule, long head of the BFT,
and distal femur.

16. The anterior oblique band (AOB) – Found in 14% of
individuals, is a band of fibrous tissue that extends
from the lateral collateral ligament to the lateral portion
of tibia. Some fibers of the anterior oblique band
(AOB) blend with posterior fibers of the iliotibial tract.
THE ARCUATE LIGAMENT - Is part of the posterolateral
ligamentous complex of the knee that is variably present,
being found in ~65% (range 47.9-71%) of knees.
It is a Y-shaped thickening of the posterolateral capsule,
which arises from the fibular styloid and divides into two
limbs:
Medial limb: curves over the popliteus muscle to join with
the oblique popliteal ligament.
Lateral limb: ascends to blend with the capsule near the
lateral gastrocnemius muscle.
SOURCE: Arcuate ligament | Radiology Reference Article |
Radiopaedia.org
THE ARCUATE LIGAMENT - Is part of the posterolateral
ligamentous complex of the knee that is variably present,
being found in ~65% (range 47.9-71%) of knees.
It is a Y-shaped thickening of the posterolateral capsule,
which arises from the fibular styloid and divides into two
limbs:

17. ARCUATE COMPLEX
STATIC STABILISERS – LCL, ARCUATE LIGAMENT AND
POPLITEUS TENDON

18. PLC STRUCTURES - LAYERS
COMMON PERONEAL NERVE
LIES B/W LAYER I AND II

19. FANELLI classification of PLC instability
TYPE A – MAINLY ROTATIONAL INSTABILITY (PLT OR PFL TEAR)
TYPE B – ROTATIONAL INSTABILITY + MILD VARUS STRESS
GAPPING (PLT+PFL+FCL)
TYPE C – MARKED VARUS AND ER INSTABILITY (DISRUPTION OF
THE PLC STRUCTURES + CRUCIATE LIG INJURY)

20. MODIFIED HUGHSTON CLASSIFICATION
EXAMINATION FINDINGS
GRADE I 0-5 MM LAT OPENING ON
VARUS STRESS
0-5* ROTATIONAL
INSTABILITY ON DIAL TEST
SPRAIN, NO TENSILE FAILURE
OF CAPSULOLIGAMENTOUS
STRUCTURES
GRADE II 6-10 MM LAT OPENING ON
VARUS STRESS
6-10* ROTATIONAL
INSTABILITY ON DIAL TEST
PARTIAL INJURIES WITH
MODERATE LIG DISRUPTION
GRADE III >10 MM LAT OPENING ON
VARUS STRESS, NO ENDPOINT
>10* ROTATIONAL
INSTABILITY ON DIAL TEST,
NO ENDPOINT
COMPLETE LIGAMENT
DISRUPTION

21. PRESENTATION
SYMPTOMS
INSTABILITY SYMPTOMS WHEN KNEE IS IN FULL EXTENSION
DIFF WITH RECIPROCATING STAIRS, PIVOTING AND CUTTING

22. PHYSICAL EXAMINATION
GAIT
STANDING VARUS ALIGNMENT
VARUS/HYPEREXTENSION THRUST ON AMBULATION

23. VARUS STRESS
LAX AT 0* - LCL + CRUCIATE INJURY (PCL/ACL)
LAX AT 30* - LCL INJURY

24. DIAL TEST
>10* ER ASYMMETRY AT 30* - ISOLATED PLC INJURY
>10* ER ASYMMETRY AT 30* AND 90* - PLC + PCL INJURY

25. ER RECURVATUM
LOWER LEG SUSPENDED BY TOES IN SUPINE POSITION :
ER+RECURVATUM OF LEG – POSITIVE
MORE CONSISTANT WITH COMBINED ACL AND PLC INJURIES

26. POSTEROLATERAL DRAWER TEST
PREREQUISITES – HIP 45* FLEXION + KNEE 80*
FLEXION + FOOT 15* ER
FORCE – COMBINED POSTERIOR DRAWER AND ER
CHECK FOR – INCREASE IN POSTEROLATERAL
TRANSLATION (LAT TIBIA ER RELATIVE TO LAT FC)

27. REVERSE PIVOT SHIFT TEST
PREREQUISITE – KNEE 90* FLEXION + ER
FORCE – VALGUS
ON EXTENSION TIBIA REDUCES WITH PALPABLE CLUNK (TIBIA REDUCES FROM POSTERIOR
SUBLUXED POSITION AT AROUND 20* FLEXION TO A REDUCED POSITION IN FULL EXTENSION)

28. PERONEAL NERVE INJURY
IN 25% OF PLC INJURIES
ALTERED SENSATION TO DORSUM OF FOOT AND WEAK ANKLE DORSIFLEXION

29. RADIOGRAPH
AVULSION FRACTURE OF FIBULA (ARCUATE FRACTURE) OR FEMORAL CONDYLE
STRESS VIEWS: B/L VARUS STRESS IN 20* FLEXION
SIDE TO SIDE DIFF IS 2.7 to 4mm - ISOLATED LCL INJURY
SIDE TO SIDE DIFF IS > 4mm – PLC INJURY

30. LONG LEG STANDING RADIOGRAPHS TO EVALUATE ALIGNMENT
IN CHRONIC PLC INJURIES
PRIMARY VARUS - TIBIOFEMORAL MALALIGNMENT
SECONDARY VARUS - LCL DEFICIENCY WITH INCREASED LATERAL OPENING
TRIPLE VARUS – REMAINING PLC DEFICIENT, OVERALL VARUS RECURVATUM ALIGNMENT
NECESSORY TO DETERMINE MECHANICAL AXISAND IF A PROXIMAL TIBIAL OSTEOTOMY FOR
CORRECTION

31. MRI – PLC STRUCTURES
Coronal proton-density–weighted MR image shows
the LCL (arrow) extending from just posterior to the femoral
epicondyle to the lateral aspect of the fibular head, where it
merges with the biceps femoris tendon. The popliteus tendon
(arrowhead) underlies the LCL at the level of the popliteus sulcus.
Axial T2-weighted fat-suppressed MR images show the normal
course and MR imaging appearance of the LCL (straight arrow),
biceps femoris tendon (arrowhead). The origin of the LCL is
immediately anterior to the femoral attachment of the lateral head
of the gastrocnemius tendon (curved arrow)
Axial T2-weighted fat-suppressed MR images show the normal
course and MR imaging appearance of the LCL (straight arrow),
biceps femoris tendon (arrowhead), and popliteus tendon (wavy
arrow)

32. Axial T2-weighted fat-suppressed MR images show the
normal course and MR imaging appearance of
the LCL (straight arrow), biceps femoris tendon
(arrowhead).
Axial T2-weighted fat-suppressed MR images show the
normal course and MR imaging appearance of
the LCL (straight arrow), biceps femoris tendon
(arrowhead), and popliteus tendon (wavy arrow).

33. Coronal proton-density–weighted and axial T2-weighted fat-
suppressed MR images shows a popliteus muscle strain, with
intramuscular edema (arrow) extending to the myotendinous
junction (arrow)
Coronal proton-density–weighted fat-suppressed MR images
show a more severe injury involving the myotendinous junction
of the popliteus (arrow), in addition to a partial tear at the
insertion of the popliteus tendon (arrowhead). The patient also
sustained a partial tear at the origin of the LCL (curved arrow)

34. Coronal proton-density–weighted fat-suppressed
MR image shows an intact PFL (arrow)
extending from the myotendinous junction of the
popliteus to the medial aspect of the fibular
styloid process.
Coronal proton-density–weighted fat-suppressed
MR image shows, in contrast, increased
intrasubstance signal intensity within
the PFL (arrow) and surrounding soft-tissue
edema, which are consistent with a partial tear.

35. TREATMENT
Clinically, injuries to the PLC or “dark side” of the knee are becoming more recognized. Undiagnosed PLC
injuries may lead to poor outcomes or failures of cruciate reconstructions, chronic instability with resulting early
onset osteoarthritis, and chronic pain. More recently, our understanding of the anatomy, biomechanics,
diagnosis, and management of PLC injuries has increased.

36. NONOPERATIVE
INDICATIONS
grade I PLC injury
isolated midsubstance grade II injury
Technique
Hinged knee brace locked in extension x4 weeks
Followed by progressive functional rehabilitation
Quad strengthening
Return to sports in 8 weeks

37. Kannus Am J Sports Med 1989 & Krukhaug et al Knee Surg Sports Traumatol
Arthrosc 1998
GRADE I & II INJURIES
Good results with early mobilization
Minimal radiographic changes at 8 years
Grade III INJURIES
Poor functional outcomes, poor strength, persistent instability
~50% had radiographic changes in medial & lateral compartments
Grade II & III treated surgically had improved varus stability & improved functional
outcomes

38. Acute (within 3 weeks) surgical intervention provides more favorable results to
late reconstruction.
Direct repair with/without augmentation
Primary reconstruction
Late reconstruction have limitations like Pericapsular scarring makes visualization
of structures difficult and Chronic injury associated with capsular stretching
SURGERY
Ranawat JAAOS 2008

39. Repair within 3 weeks
Repair ligament and tendon bony & soft tissue avulsions
Popliteal avulsion off femur
LCL / PFL / Biceps femoris avulsions off fibular head
IT band avulsion off Gerdy’s tubercle
Mid-1/3 lateral capsular ligament
REPAIR VERSUS RECONSTRUCTION
Repair of LCL, popliteus tendon and/or popliteofibular
ligament should be performed if structures can
be anatomically reduced to their attachment site, otherwise
perform reconstruction
Augment PLC repair with free graft if repair tenuous
Avulsion fracture of fibular head can be treated with screws
or suture anchors
Results are good when combination of repair & reconstruction done within 3 weeks

40. REPAIR VERSUS RECONSTRUCTION
Stannard et al Am J Sports Med 2005
57 knees (56 patients) with minimum 24-months f/up
44 (77%) with multiligamentous injury
Repair those with adequate tissue quality, done < 3 weeks
Early motion rehabilitation protocol
Failure rate (p=.03)
Reconstruction 9% (2/22)
Repair 37% (13/35)
11/13 sustained mid-substance tissue stretch / failure
Successful reconstruction in 14 pts with failed initial treatment
Overall reconstruction failure 5% (2/36)

41. REPAIR VERSUS RECONSTRUCTION
Levy et al Am J Sports Med 2010
28 knees included in study
10 with repair then staged cruciate reconstruction, Average f/up 34 months
18 simultaneous reconstructions (FCL/PLC & cruciates), Average f/up 28 months
Failure rate (p=.04)
Repair 40% (4/10)
Reconstruction 6% (1/18)
Conclusion: reconstruction of PLC is more reliable than repair alone in the setting of MLI

44. If other posterior cruciate ligament structures require
reconstruction, those are completed before fixation of the
reconstructed popliteus tendon.
With the graft well seated in the femoral socket, it is first fixed
to the femoral tunnel with a bioabsorbable screw (usually 1 size
larger than the tunnel diameter).
After the graft is tensioned by repetitive pumping of the knee
through a full range of motion, the tibial fixation is then
completed with another bioabsorbable interference screw (again
1 size larger than the tunnel diameter). The tibial bio-
interference screw is advanced to the posterior aperture of the
tibial tunnel while the knee is held at 30° flexion, with neutral
tibial rotation, and with approximately 22 N of tension on the
graft.

45. ANATOMICAL PLT RECONSTRUCTION
A tibial PCL drill guide (Arthrex, Naples, USA) was inserted
through the anteromedial portal, introduced in the cranial gap
between the cruciate ligaments and pushed forward into the
posterolateral recessus. The tip of the drill guide was placed in
the middle of the distal part of the sulcus popliteus. The anterior
start point of the drill guide was placed between the lateral edge
of the tibial tuberosity and the medial edge of Gerdy’s tubercle.
The tibial channel was drilled with a 6-mm reamer. Following
this, the tibial channel for the PCL reconstruction was applied in
a standard manner.
For anatomical placement of the femoral tunnel,
high anterolateral portal used At 20–30 of knee
flexion
Recommend a graft length for PLT
reconstruction of at least 11–12 cm.
Femoral PFT fixation done with
bioabsorbable screw.
The femoral PCL tunnel was then drilled, the
PCL graft was shuttled in the knee and the
femoral termination fixed with a
bioabsorbable screw. At 70–90 of flexion, the
tibial fixation of the popliteus graft and the
PCL graft were performed.

46. Graft passed through fibula tunnel, If the PCL requires
reconstruction, it is completed before fixation of the
reconstructed PFL. The surgeon completes the PFL
reconstruction by pulling on the passing suture and tensions the
graft from the medial side of the knee. With the graft well
seated in the femoral socket, it is first fixed to the femoral
tunnel with a bio-absorbable screw (7 mm in diameter). After
the graft is tensioned by repetitive pumping of the knee through
a full range of motion, the fibular fixation is then completed
with another bio-absorbable interference screw (7 mm in
diameter). The fibular biointerference screw is advanced to the
posterior aperture of the fibular tunnel, while the knee is held at
30° of flexion and neutral tibial rotation with approximately
22N of tension on the graft.

47. STABILIZATION OF THE POSTEROLATERAL JOINT CAPSULE/ NON ANATOMICAL

48. FIBULA BASED/ Technique is similar to the popliteus tendon bypass graft by Frosch et al., transseptal portal
An armed gracilis or semitendinosus tendon graft with a
minimum length of 20 cm was fixed to the femoral PLT
footprint first and subsequently shuttled along the PLT’s native
course, through the fibular drill tunnel from posteromedial to
anterolateral and finally attached to the femoral LCL footprint
drill tunnel. Fixation of the graft is performed by a bio
interference screw in the fibula 90* and in the femur in 20-30*
flexion angles.

49. MODIFIED FRINGS et.al, an accessory inferior posterolateral portal

50. Liu et al. described another similar technique in 2020, but instead of using a transseptal approach,
arthroscopic visualization of the posterolateral corner is enabled by establishing a posterolateral portal
5 mm above and posterior to the tip of the fibular styloid under arthroscopic visualization from a high
lateral portal at the femoral PLT footprint, so this visualization is likely restricted in comparison to a
transseptal view Through the posterolateral portal the fibular PFL insertion site is exposed after
radiofrequency debridement.

51. To address patients with higher grade instabilities (Type 3), Hermanowicz et al. described an arthroscopic-assisted
fibula-/tibia-based combined reconstruction of PLC and LCL in 2019. Reconstructing both ligaments required two
autologous tendon grafts (semitendinosus tendon for PLT, gracilis tendon for LCL).

52. TUNNELING FOR LCL

53. Another arthroscopic-assisted fibula-/tibia-based combined reconstruction of PLC and LCL in 2019
Procedure follows the well-established open reconstruction
described by Laprade et al.
The popliteus bypass graft (min. 11 cm) is attached to the femur,
then shuttled along the popliteus tendon native path and through
the tibia. After femoral attachment, the second graft (min.
17 cm) is passed under the iliotibial band to the anterolateral
fibular tunnel, through the fibula and ultimately through the
tibial tunnel from posterior to anterior. The LCL graft is fixed at
20° of knee flexion in the fibular tunnel and the popliteus
bypass graft at 70° of knee flexion in the tibial tunnel, both with
biointerference screws.
ADVANTAGE – SPARES PTFJ

55. CHRONIC KNEE INSTABILITY WITH MALALIGNMENT

57. SEQUENCE OF FIXATION IN COMBINED INJURIES
FIX FEMORAL ATTACHMENT OF ACL AND PCL FIRST
TIBIAL FIXATION OF PCL
FIBULAR ATTACHMENT OF LCL AT 30* FLEXION AND VALGUS
STRESS
TIBIAL FIXATION OF PLC IN 60* FLEXION
TIBIAL FIXATION OF ACL IN 20* FLEXION