Posterolateral knee injuries
Encyclopedia
The posterolateral corner (PLC) of the knee
is a complex area of the knee formed by the interaction of multiple structures. Injuries to the posterolateral corner can be debilitating to patients and require prompt recognition and treatment to avoid long term consequences. Injuries to the PLC often occur in combination with other ligament
ous injuries to the knee; most commonly the anterior cruciate ligament
(ACL) and posterior cruciate ligament
(PCL). As with any injury
, an in-depth understanding of the anatomy
and functional interactions of the posterolateral corner is critical to diagnosing and treating injuries here.
, fibula, lateral femur, iliotibial band (IT band), the long and short heads of the biceps femoris tendon
, the fibular (lateral) collateral ligament (FCL)
, the popliteus tendon
, the popliteofibular ligament, the lateral gastrocnemius tendon, and the fabellofibular ligament. It has been reported that among these, the 3 most important static stabilizers of the posterolateral knee are the FCL, popliteus tendon, and popliteofibular ligament Studies have reported that these structures work together to stabilize the knee by restraining varus
, external rotation
and combined posterior translation with external rotation.
, patella, tibia, and fibula. In the posterolateral corner, the bony landmarks of the tibia, fibula and femur serve as the attachment sites of the ligaments and tendons that stabilize this portion of the knee. The patella plays no significant role in the posterolateral corner. The bony shape of the posterolateral knee, with the two convex opposing surfaces of the lateral femoral condyle and the lateral tibial plateau, makes this portion of the knee inherently unstable compared to the medial aspect. Thus, it has a much higher risk of not healing properly after injury than the medial aspect of the knee.
The popliteofibular ligament (PFL) connects the popliteus muscle at the musculotendinous junction to the posterior and medial portion of the fibular styloid. It has two divisions, anterior and posterior, and acts to stabilize the knee during external rotation.
The mid-third lateral capsular ligament is made of a part of the lateral capsule as it thickens and extends along the femur, attaching just anterior to the popliteus attachment at the lateral epicondyle, and extends distally to the tibia attaching slightly posterior to Gerdy's tubercle
and anterior to the popliteal hiatus. In addition, it has a capsular attachment at the lateral meniscus
. It has two divisions, the meniscofemoral component and the meniscotibial component named for the areas they span, respectively. Studies suggest that the mid-third capsular ligament functions as a secondary varus stabilizer in the knee.
, and capsuloosseus layer of the IT band. The fabellofibular ligament is actually a thickening of the capsular arm of the biceps femoris as it runs distally to the fibula. The direct arm attaches to the posterior and lateral aspect of the fibular styloid. The anterior arm attaches to the tibia at the same site as the mid-third lateral capsular ligament and is often injured in Segond fracture
s. Injuries to the biceps femoris tendons have been reported in patients with anterolateral-anteromedial rotatory instability.
The popliteus tendon’s main attachment is on the femur at the proximal portion of the popliteus sulcus. As the tendon runs posteriorly and distally behind the knee, it gives off 3 fascicles that attach to and stabilize the lateral meniscus. The popliteus tendon provides static and dynamic stabilization to the knee during posterolateral rotation.
The iliotibial band (IT band) is mainly divided into two layers, the superficial and capsuloosseus layers. The superficial layer runs along the lateral knee and attaches to Gerdy’s tubercle and sends a deeper portion that attaches to the lateral intermuscular septum
(IM septum). The capsuloosseus layer extends from the IM septum and merges with the short head of the biceps femoris attaching with it at the anterolateral aspect of the tibia. The IT band stabilizes the posterolateral knee by helping to prevent varus opening.
The lateral gastrocnemius tendon inserts on the supracondylar process of the femur slightly posterior to the FCL. Injuries involving this tendon are typically associated with severe trauma
s and are not often seen.
(blood in the knee joint) was 9.1%.
, patients may experience numbness, tingling and weakness of the ankle dorsiflexors and great toe extensors, or a footdrop.
tear. This can make the diagnosis difficult and calls for the use of plain film radiographs and MRI to aid in the diagnosis. During the physical exam, it is imperative to assess a patient for signs of nerve injury as up to 15% of PLC injuries have associated nerve damage. Numbness, tingling, and/or dorsiflexor
/great toe extensor muscle weakness
all may suggest possible nerve damage.
are useful to look for Segond fractures and fibular head avulsion fracture
s. Bilateral varus stress AP radiographs comparing the injured leg to the normal side are useful in assessing the lateral joint space for opening after a potential injury. More than a 2.7 mm increase between sides indicates a fibular collateral ligament tear, while greater than 4.0 mm indicates with a grade III posterolateral knee injury. Posterior stress radiographs taken with the patient kneeling show the amount of posterior tibial translation in both knees and are helpful to diagnose PCL insufficiency and combined injuries. Between 0–2 mm increased posterior translation between the affected and healthy knees is normal, 2–7 mm indicates a partial tear, 8–11 mm suggests a complete tear and greater than 12 mm suggests a combined PCL and PLC injury.
films are useful, thin slice (2 mm ) coronal oblique images should also be obtained when looking for PLC injuries. Coronal oblique images should include the fibular head and styloid to allow for evaluation of the FCL and popliteus tendon.
of the lower extremity, there are a set of specialized tests that must be synthesized to specifically check for injuries to the posterolateral corner. It is always important when evaluating an extremity for injury to compare it with the normal side to make sure you are not seeing a normal variation within that patient:
observed to look for a varus thrust gait, which is indicative of these types of injuries. As the foot makes contact with the ground, the compartments of the knee should remain tight and stabilize the joint through the impact and movements of walking. In posterolateral corner injuries, the lateral compartment
has lost all or part of its stability and cannot maintain normal anatomic positioning when stressed. A varus thrust gait occurs as the foot strikes and the lateral compartment opens due to the forces applied on the joint. This forces the joint to sublux into a varus position to compensate. In chronic injuries, patients sometimes learn to walk with a partially flexed knee to alleviate the instability caused by their injury. Patients with medial compartment arthritis
can also demonstrate a varus thrust gait, so it is important to differentiate between the two causes using plain radiographs. Patients with PLC injuries will have increased lateral gapping on varus stress radiographs, while arthritis patients have no gapping but should show signs of joint space narrowing, subchondral cysts, osteophytes, and/or sclerotic bone changes.
is another useful tool to diagnose and assess injuries to the posterolateral corner. Arthroscopy is useful in two ways. First, a patient undergoing arthroscopy is placed under anesthesia
which allows for a complete physical examination using the specialized tests described above, which can be difficult with the patient awake. A prospective study that looked at 30 patients undergoing arthroscopy found all of them to have a positive “drive through sign” during evaluation. A drive through sign occurs when there is more than 1 cm of lateral joint opening when a varus stress is applied to the knee which allows the surgeon to easily pass the arthroscope between the lateral femoral condyle and tibia . Second, arthroscopy allows the surgeon to visualize individual structures in the posterolateral knee. The specific structures that can be evaluated are the popliteus tendon attachment on the femur, the popliteomensical fascicles, the coronary ligament of the posterior horn of the lateral meniscus, and the meniscofemoral and meniscotibial portions of the mid-third lateral capsular ligament. Examination of these structures allows injuries to be indentified and will direct the placement of incisions for repair or reconstruction.
.
, the patient can begin exercises to improve range of motion
and begin bearing weight on crutches only. The crutches can be discontinued when the patient can walk without limping. Quadriceps strengthening exercises are allowed, but no isolated hamstring
exercises should be attempted for 6 – 10 weeks following the injury. If after 10 weeks, pain or instability continue, the patient should be reevaluated for surgical treatment.
and the body’s repair mechanisms. Chronic PLC injuries are less likely to be amenable to repair due to complications from scar tissue and limb malalingment; these injuries will likely necessitate reconstruction. Knees in varus alignment and which have chronic injuries (evaluated by long leg standing radiographs) will require a staged procedure that starts with an opening wedge osteotomy
. This procedure lessens the constraint on the knee and prevents the reconstruction grafts from stretching out. If the patient still has instability, the PLC reconstruction will take place approximately 6 months later. MRI scans will be helpful in determining whether torn structures are amenable to repair or will require reconstruction with allografts.
The structures considered for potential reconstruction are the fibular collateral ligament, popliteus tendon, and popliteofemoral ligament. The FCL and/or popliteus tendon are only considered for acute repair when they are avulsed off bone and can be reattached anatomically with the knee in extension. The PFL can be repaired when it is torn directly off of the fibular head and the popliteus is still intact. Reconstruction is preferred when the ligaments/tendons have mid-substance tears or other tears not amenable to repair. Reconstruction of either the FCL or popliteus tendon is typically completed utilizing a patient’s hamstring (semitendinous) for a graft; however when reconstructing both the FCL and popliteus an Achilles tendon
graft from a cadaver is preferred.
d or anchored back to their bony attachments. The goal is to always achieve a stable and secure repair so that patients can initiate ROM exercises. Certain situations require more complicated repairs:
Femoral avulsions of the FCL or popliteus typically require a slightly more complex repair using a recess procedure in which stitches are placed through a bone tunnel and around the avulsed structure to proved further stabilization and return to range of motion exercises.
Avulsion fractures that occur at the fibular head or fibular styloid typically are caused by detachment of the popliteofibular ligament, direct arm of either the long or short heads of the biceps femoris or FCL. These fractures are best repaired with nonabsorbable suture or with wires. If the fracture is large enough, open fixation with surgical hardware may be required.
Midsubstance tears of the FCL or popliteus tendon are best treated with anatomic reconstructions.
in the joint. In addition, failing to address a chronic posterolateral knee injury when repairing a deficient ACL or PCL has been shown to cause increased forces of the graft leading to cruciate reconstruction graft stretching and/or failure.
es after 6 weeks, but the weight should be very light. Jogging
and more aggressive strength training can begin around 4 – 6 months at the surgeon and physical therapists discretion. Patients should not be casted after surgery unless absolutely necessary.
Other less common surgical complications include deep vein thrombosis
(DVTs), infection, blood loss, and nerve/artery damage. The best way to avoid these complications is to preemptively treat them. DVTs are typically treated prophylactically with either aspirin
or sequential compression device
s (SCDs). In high risk patients there may be a need for prophylactic administration of low molecular weight heparin
(LMWH). In addition, having a patient get out of bed and ambulate soon after surgery is a time honored way to prevent DVTs. Infection is typically controlled by administering 1 gram of the antibiotic cefazolin
(Ancef) prior to surgery. Excessive blood loss and nerve/artery damage are rare occurrences in surgery and can usually be avoided with proper technique and diligence; however, the patient should be warned of these potential complications, especially in patients with severe injuries and scarring.
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
is a complex area of the knee formed by the interaction of multiple structures. Injuries to the posterolateral corner can be debilitating to patients and require prompt recognition and treatment to avoid long term consequences. Injuries to the PLC often occur in combination with other ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
ous injuries to the knee; most commonly the anterior cruciate ligament
Anterior cruciate ligament
The anterior cruciate ligament is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle , based on its anatomical position, it is referred to as the cranial cruciate ligament.The ACL originates from deep within the notch of the distal femur...
(ACL) and posterior cruciate ligament
Posterior cruciate ligament
The posterior cruciate ligament is one of the four major ligaments of the knee. It connects the posterior intercondylar area of the tibia to the medial condyle of the femur...
(PCL). As with any injury
Injury
-By cause:*Traumatic injury, a body wound or shock produced by sudden physical injury, as from violence or accident*Other injuries from external physical causes, such as radiation injury, burn injury or frostbite*Injury from infection...
, an in-depth understanding of the anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
and functional interactions of the posterolateral corner is critical to diagnosing and treating injuries here.
Anatomy and Function
Structures found in the posterolateral knee include the tibiaTibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
, fibula, lateral femur, iliotibial band (IT band), the long and short heads of the biceps femoris tendon
Biceps femoris muscle
The biceps femoris is a muscle of the posterior thigh. As its name implies, it has two parts, one of which forms part of the hamstrings muscle group.-Origin and insertion:It has two heads of origin;...
, the fibular (lateral) collateral ligament (FCL)
Fibular collateral ligament
-External links:*...
, the popliteus tendon
Popliteus muscle
The popliteus muscle in the leg is used to unlock the knee during walking/running by laterally rotating the femur on the tibia during a closed chain movement ....
, the popliteofibular ligament, the lateral gastrocnemius tendon, and the fabellofibular ligament. It has been reported that among these, the 3 most important static stabilizers of the posterolateral knee are the FCL, popliteus tendon, and popliteofibular ligament Studies have reported that these structures work together to stabilize the knee by restraining varus
Varus
-People:*Publius Attius Varus , Roman governor of Africa.*Publius Quinctilius Varus , politician of the Roman Empire.*Quinctilius Varus -People:*Publius Attius Varus (died 17 March 45 BCE), Roman governor of Africa.*Publius Quinctilius Varus (46 BCE - 9 CE), politician of the Roman...
, external rotation
External rotation
External rotation is rotation away from the center of the body.The muscles of external rotation include:* of arm/humerus at shoulder** Deltoid muscle** Infraspinatus** Teres minor* of thigh/femur at hip ** Gluteus maximus...
and combined posterior translation with external rotation.
Bones
The bones that make up the knee are the femurFemur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
, patella, tibia, and fibula. In the posterolateral corner, the bony landmarks of the tibia, fibula and femur serve as the attachment sites of the ligaments and tendons that stabilize this portion of the knee. The patella plays no significant role in the posterolateral corner. The bony shape of the posterolateral knee, with the two convex opposing surfaces of the lateral femoral condyle and the lateral tibial plateau, makes this portion of the knee inherently unstable compared to the medial aspect. Thus, it has a much higher risk of not healing properly after injury than the medial aspect of the knee.
Ligaments
The fibular collateral ligament (FCL) connects the femur to the fibula. It attaches on the femur just proximal and posterior to the femoral lateral epicondyle and extends approximately 70 mm down the knee to attach to the fibular head. From 0° to 30° of knee flexion, the FCL is the main structure preventing varus (link to varus) opening of the knee joint.The popliteofibular ligament (PFL) connects the popliteus muscle at the musculotendinous junction to the posterior and medial portion of the fibular styloid. It has two divisions, anterior and posterior, and acts to stabilize the knee during external rotation.
The mid-third lateral capsular ligament is made of a part of the lateral capsule as it thickens and extends along the femur, attaching just anterior to the popliteus attachment at the lateral epicondyle, and extends distally to the tibia attaching slightly posterior to Gerdy's tubercle
Gerdy's tubercle
Gerdy's tubercle is a lateral tubercle of the tibia, located where the fascia lata or iliotibial band inserts. It was named after French surgeon Pierre Nicolas Gerdy ....
and anterior to the popliteal hiatus. In addition, it has a capsular attachment at the lateral meniscus
Lateral meniscus
The lateral meniscus, also called the external semilunar fibrocartilage, is a fibrocartilaginous band that spans the lateral side of the interior of the knee joint. It is one of two menisci of the knee, the other being the medial meniscus. It is nearly circular and covers a larger portion of the...
. It has two divisions, the meniscofemoral component and the meniscotibial component named for the areas they span, respectively. Studies suggest that the mid-third capsular ligament functions as a secondary varus stabilizer in the knee.
Tendons & Muscles
The long and short heads of the biceps femoris each branch off into 5 attachment arms as they course distally in the knee. In the posterolateral knee, the long head has 3 important anatomic attachments. The direct arm attachment is on the posterolateral fibular styloid, the anterior arm lateral to the FCL and the lateral aponeurotic arm on the posterior and lateral portion of the FCL. The short head of the biceps also has 3 important arms in the posterolateral knee. The capsular arm attaches to the posterolateral capsule as well as the fibula, just lateral to the styloid and provides a strong attachment to the capsule, lateral gastrocnemius tendonGastrocnemius muscle
In humans, the gastrocnemius muscle is a very powerful superficial pennate muscle that is in the back part of the lower leg. It runs from its two heads just above the knee to the heel, and is involved in standing, walking, running and jumping. Along with the soleus muscle it forms the calf muscle...
, and capsuloosseus layer of the IT band. The fabellofibular ligament is actually a thickening of the capsular arm of the biceps femoris as it runs distally to the fibula. The direct arm attaches to the posterior and lateral aspect of the fibular styloid. The anterior arm attaches to the tibia at the same site as the mid-third lateral capsular ligament and is often injured in Segond fracture
Segond fracture
The Segond fracture is a type of avulsion fracture of the lateral tibial condyle of the knee, immediately beyond the surface which articulates with the femur.-History and incidence:...
s. Injuries to the biceps femoris tendons have been reported in patients with anterolateral-anteromedial rotatory instability.
The popliteus tendon’s main attachment is on the femur at the proximal portion of the popliteus sulcus. As the tendon runs posteriorly and distally behind the knee, it gives off 3 fascicles that attach to and stabilize the lateral meniscus. The popliteus tendon provides static and dynamic stabilization to the knee during posterolateral rotation.
The iliotibial band (IT band) is mainly divided into two layers, the superficial and capsuloosseus layers. The superficial layer runs along the lateral knee and attaches to Gerdy’s tubercle and sends a deeper portion that attaches to the lateral intermuscular septum
Intermuscular septum
Intermuscular septum can refer to:* medial intermuscular septum of arm* medial intermuscular septum of thigh* lateral intermuscular septum of arm* lateral intermuscular septum of thigh...
(IM septum). The capsuloosseus layer extends from the IM septum and merges with the short head of the biceps femoris attaching with it at the anterolateral aspect of the tibia. The IT band stabilizes the posterolateral knee by helping to prevent varus opening.
The lateral gastrocnemius tendon inserts on the supracondylar process of the femur slightly posterior to the FCL. Injuries involving this tendon are typically associated with severe trauma
Trauma
Trauma can refer to:-In psychology and medicine:* Trauma , an often serious and body-altering physical injury, such as the removal of a limb...
s and are not often seen.
Epidemiology
Isolated and combined posterolateral knee injuries are difficult to accurately diagnose in patients presenting with acute knee injuries. The incidence of isolated posterolateral corner injuries has been reported to be between 13% and 28%. Most PLC injuries accompany an ACL or PCL tear, and can contribute to ACL or PCL reconstruction graft failure if not recognized and treated. A study by LaPrade et al in 2007 showed the incidence of posterolateral knee injuries in patients presenting with acute knee injuries and hemarthrosisHemarthrosis
Hemarthrosis is a bleeding into joint spaces.-Causes:It usually follows injury but occurs mainly in patients with a predisposition to hemorrhage such as those being treated with warfarin and patients with hemophilia.It can be associated with knee joint arthroplasty.-Treatment:In hemophilia it may...
(blood in the knee joint) was 9.1%.
Causes
The most common mechanisms of injury to the posterolateral corner are a hyperextension injury (contact or non-contact), direct trauma to the anteromedial knee, and noncontact varus force to the knee.Symptoms
Patients often complain of pain and instability at the joint. With concurrent nerve injuriesNerve injury
Nerve injury is injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injury. Most systems attempt to correlate the degree of injury with symptoms, pathology and prognosis...
, patients may experience numbness, tingling and weakness of the ankle dorsiflexors and great toe extensors, or a footdrop.
Diagnosis
The majority of posterolateral knee injuries occur in combination with another ligamentous injury, such as a cruciate ligamentCruciate ligament
Cruciate ligaments are pairs of ligaments arranged like a letter X. They occur in several joints of the body, such as the knee...
tear. This can make the diagnosis difficult and calls for the use of plain film radiographs and MRI to aid in the diagnosis. During the physical exam, it is imperative to assess a patient for signs of nerve injury as up to 15% of PLC injuries have associated nerve damage. Numbness, tingling, and/or dorsiflexor
Dorsiflexion
Dorsiflexion is the movement which decreases the angle between the dorsum of the foot and the leg, so that the toes are brought closer to the shin. The movement moving in opposite directions is called plantarflexion...
/great toe extensor muscle weakness
Muscle weakness
Muscle weakness or myasthenia is a lack of muscle strength. The causes are many and can be divided into conditions that have true or perceived muscle weakness...
all may suggest possible nerve damage.
Radiographs
Normal antero-posterior (AP) radiographsRadiography
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
are useful to look for Segond fractures and fibular head avulsion fracture
Avulsion fracture
An avulsion fracture is a bone fracture which occurs when a fragment of bone tears away from the main mass of bone as a result of physical trauma. This can occur at the ligament due to the application forces external to the body or at the tendon due to a muscular contraction that is stronger than...
s. Bilateral varus stress AP radiographs comparing the injured leg to the normal side are useful in assessing the lateral joint space for opening after a potential injury. More than a 2.7 mm increase between sides indicates a fibular collateral ligament tear, while greater than 4.0 mm indicates with a grade III posterolateral knee injury. Posterior stress radiographs taken with the patient kneeling show the amount of posterior tibial translation in both knees and are helpful to diagnose PCL insufficiency and combined injuries. Between 0–2 mm increased posterior translation between the affected and healthy knees is normal, 2–7 mm indicates a partial tear, 8–11 mm suggests a complete tear and greater than 12 mm suggests a combined PCL and PLC injury.
MRI
High quality MRI images (1.5 T magnet or higher ) of the knee can be extremely useful to diagnose injuries to the posterolateral corner and other major structures of the knee. While the standard coronal, sagittal and axialAxial
Axial may mean:* Along the same line as an axis of rotation in geometry* A type of modal frame in music* One of several anatomical directions in an animal body* Axial age, the period from 800 to 200 BC in China, India and the western world...
films are useful, thin slice (2 mm ) coronal oblique images should also be obtained when looking for PLC injuries. Coronal oblique images should include the fibular head and styloid to allow for evaluation of the FCL and popliteus tendon.
Specialized Tests
In addition to a complete physical examinationPhysical examination
Physical examination or clinical examination is the process by which a doctor investigates the body of a patient for signs of disease. It generally follows the taking of the medical history — an account of the symptoms as experienced by the patient...
of the lower extremity, there are a set of specialized tests that must be synthesized to specifically check for injuries to the posterolateral corner. It is always important when evaluating an extremity for injury to compare it with the normal side to make sure you are not seeing a normal variation within that patient:
- External Rotation Recurvatum Test - One of the first tests developed to assess the PLC, the external rotation recurvatum test is performed with the patient lying supineSupineIn grammar a supine is a form of verbal noun used in some languages.-In Latin:In Latin there are two supines, I and II . They are originally the accusative and dative or ablative forms of a verbal noun in the fourth declension, respectively. The first supine ends in -um. It has two uses. The first...
. The practitioner stabilizes the distal thighThighIn humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb.The single bone in the thigh is called the femur...
with one hand while lifting the great toe with the other. The injured side is compared to the healthy one and a positive test is indicated by an increased amount of recurvatum, or hyperextension, in the affected knee. Increased recurvatum indicates possible combined injuries to the posterolateral corner and cruciate ligaments. The increase on recurvatum is best reported as the heel height off the examining table.
- Varus stress test at 0° and 30° - Varus stress testing is accomplished while the patient is lying supine on an examination table. The physician supports the thigh against the side of the exam table and applies a varus force to the knee joint while holding the ankleAnkleThe ankle joint is formed where the foot and the leg meet. The ankle, or talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus bone in the foot...
or footFootThe foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...
, first at 0°of flexion and then at 30°. As the knee is stressed, the practitioner should feel for increased gappingGappingGapping is a term in linguistics that refers to clauses in which all verbal elements have been omitted, but in which internal arguments of the verb remain...
at the lateral joint space. Gapping can be graded based on the amount the joint opens under stress; grade I causes painPainPain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
, but with no gap present, grade II causes some gapping, but a definite endpoint is present, and grade III causes significant gapping with no definite endpoint felt. A negative varus stress test shows no difference between either knee at 0° or 30°. Increased gapping at 0° of flexion typically reflects a serious posterolateral injury with a high probability of accompanying cruciate ligament involvement. Lower grades at 30° are more suggestive of partial tears of the FCL or mid-third lateral capsular ligament, while higher grades indicate complete tears of the FCL and damage to other posterolateral structures.
- Dial Test (posterolateral rotation test) - The dial test can be performed with a patient lying supine or prone. With the patient supine and the knees flexed 30° off the table, stabilize the thigh and externally rotate the foot. As the foot rotates, watch for external rotation of the tibial tubercle of the affected knee compared to the healthy one. A difference of greater than 10-15° indicates a positive test and likely injuries to the posterolateral knee. Next, repeat the test with the patient’s knees flexed at 90°. Increased rotation at 90° indicates a combined PCL and posterolateral knee injury. If the rotation decreases compared to 30°, then an isolated PLC injury has occurred. Beware of a possible medial knee injury in the face of a positive dial test.
- Posterolateral Drawer Test - The posterolateral drawer testDrawer testThe drawer test is a test used by physicians to detect rupture of the cruciate ligaments in the knee. The patient should be supine with the hips flexed to 45 degrees, the knees flexed to 90 degrees and the feet flat on table. The examiner sits on the patient's feet and grasps the patient's tibia...
is similar to the commonly known posterior drawer test for PCL stability. Have the patient lie on their back with the knee flexed at 90° and externally rotate the foot to approximately 15°. While stabilizing the foot, apply a posterolateral rotation force to the tibia and watch for the amount of posterolateral rotation. Increased mobilityMobilityMobility may refer to:* Mobility * "Mobiliy" , a song by Moby* Mobility * Mobility , the ability of military units or weapon systems to move to an objective-See also:* Academic mobility* Apprentices mobility...
and posterolateral rotation compared to the contralateral normal side usually indicates an injury to the popliteus complex.
- Reverse Pivot Shift Test - The reverse pivot shift test is almost exactly as its name implies, a reverse of the pivot shift test. The patient lies on their back with their knee flexed to between 45° and 60° and their foot externally rotated. The practitioner applies a valgus force while slowly extending the knee. A clunk will be felt around 30° of knee flexion if the subluxedSubluxationA subluxation may have different meanings, depending on the medical specialty involved. It implies the presence of an incomplete or partial dislocation of a joint or organ. The World Health Organization defines both the medical subluxation and the chiropractic subluxation...
or dislocated jointDislocation (medicine)Joint dislocation, or luxation , occurs when bones in a joint become displaced or misaligned. It is often caused by a sudden impact to the joint. The ligaments always become damaged as a result of a dislocation...
has reduced. This occurs as the iliotibial band changes from a knee flexor to extensor around 30°. Again, the affected knee should be compared the normal side to rule out a false positive test.
- Lachman & Posterior drawer tests - Increased anterior translation on the Lachman test is found when the patient has suffered a combined ACL and PLC injury. Increased posterior translation on the posterior drawer test indicates a combined posterior cruciate ligament tear with the PCL injury.
- Figure 4 Test - The patient lies supine and flexes their affected knee to approximately 90° then crosses it over the normal side with the foot across the knee and the hip externally rotated. The practitioner applies a varus stress on the joint by pushing the affected knee towards the exam table. This places tension on the posterolateral structures of the knee, especially the popliteus complex and popliteomeniscal fascicles. If these structures have been disrupted by injury, there is no tension to stabilize the lateral meniscus and the lateral meniscus can displace medially into the joint causing the patient pain and reproducing their symptoms at the lateral joint line. As always, the injured knee should be compared to the contralateral normal side.
Gait Analysis
Patients with knee injuries suspected to involve the posterolateral corner should have their gaitGait
Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed, terrain, the need to maneuver, and energetic efficiency...
observed to look for a varus thrust gait, which is indicative of these types of injuries. As the foot makes contact with the ground, the compartments of the knee should remain tight and stabilize the joint through the impact and movements of walking. In posterolateral corner injuries, the lateral compartment
Lateral compartment of leg
The lateral compartment of the leg is supplied by the superficial fibular nerve.Its proximal and distal arterial supply consists of perforating branches of the anterior tibial artery and fibular artery....
has lost all or part of its stability and cannot maintain normal anatomic positioning when stressed. A varus thrust gait occurs as the foot strikes and the lateral compartment opens due to the forces applied on the joint. This forces the joint to sublux into a varus position to compensate. In chronic injuries, patients sometimes learn to walk with a partially flexed knee to alleviate the instability caused by their injury. Patients with medial compartment arthritis
Arthritis
Arthritis is a form of joint disorder that involves inflammation of one or more joints....
can also demonstrate a varus thrust gait, so it is important to differentiate between the two causes using plain radiographs. Patients with PLC injuries will have increased lateral gapping on varus stress radiographs, while arthritis patients have no gapping but should show signs of joint space narrowing, subchondral cysts, osteophytes, and/or sclerotic bone changes.
Arthroscopy
ArthroscopyArthroscopy
Arthroscopy is a minimally invasive surgical procedure in which an examination and sometimes treatment of damage of the interior of a joint is performed using an arthroscope, a type of endoscope that is inserted into the joint through a small incision...
is another useful tool to diagnose and assess injuries to the posterolateral corner. Arthroscopy is useful in two ways. First, a patient undergoing arthroscopy is placed under anesthesia
Anesthesia
Anesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
which allows for a complete physical examination using the specialized tests described above, which can be difficult with the patient awake. A prospective study that looked at 30 patients undergoing arthroscopy found all of them to have a positive “drive through sign” during evaluation. A drive through sign occurs when there is more than 1 cm of lateral joint opening when a varus stress is applied to the knee which allows the surgeon to easily pass the arthroscope between the lateral femoral condyle and tibia . Second, arthroscopy allows the surgeon to visualize individual structures in the posterolateral knee. The specific structures that can be evaluated are the popliteus tendon attachment on the femur, the popliteomensical fascicles, the coronary ligament of the posterior horn of the lateral meniscus, and the meniscofemoral and meniscotibial portions of the mid-third lateral capsular ligament. Examination of these structures allows injuries to be indentified and will direct the placement of incisions for repair or reconstruction.
Treatment
Treatment of posterolateral corner injuries varies with the location and grade of severity of the injuries. Patients with grade I and II (partial) injuries to the posterolateral corner can usually be managed conservatively. Studies have reported that patients with grade III (complete) injuries do poorly with conservative management and typically will require surgical intervention followed by rehabilitationRehabilitation
-Mental health:* Drug rehabilitation* Rehabilitation , the rehabilitation of criminal behavior.* Rehabilitation , therapy aimed at improving neurocognitive function that has been lost or diminished by disease or traumatic injury...
.
Nonoperative Treatment
Conservative treatment relies on immobilizing the knee in full extension to allow the stretched or torn ligaments to heal. It is imperative that the patient keep the knee immobilized and are do not bear weight on the joint for 3 to 4 weeks to allow sufficient time for the structures to heal. Following immobilizationImmobilization
Immobilization in soil science is when organic matter decomposes and is absorbed by micro-organisms, therefore preventing it being accessible to plants. Immobilization is the opposite of mineralization....
, the patient can begin exercises to improve range of motion
Range of motion
Range of motion , is the distance that a movable object may normally travel while properly attached to another object. It is also called range of travel, particularly when talking about mechanical devices and in mechanical engineering fields...
and begin bearing weight on crutches only. The crutches can be discontinued when the patient can walk without limping. Quadriceps strengthening exercises are allowed, but no isolated hamstring
Hamstring
In human anatomy, the hamstring refers to any one of the three posterior thigh muscles, or to the tendons that make up the borders of the space behind the knee. In modern anatomical contexts, however, they usually refer to the posterior thigh muscles, or the tendons of the semitendinosus, the...
exercises should be attempted for 6 – 10 weeks following the injury. If after 10 weeks, pain or instability continue, the patient should be reevaluated for surgical treatment.
Operative Treatment
This portion of the knee is felt to contain the most complex anatomy and to be the rarest type of knee injury. For this reason, consideration should be given to referral to a complex knee specialist for treatment. Surgical treatment of posterolateral corner injuries depend on whether the injury is of an acute or chronic nature and whether it is isolated to the posterolateral corner or combined with another ligamentous injury. Operative treatment is aimed at an anatomical repair or reconstruction rather than a non-anatomic reconstruction of the torn structures when possible, because this provides the highest odds of a successful return to function. The optimal time for treatment of acute injuries is within the first 3 weeks to avoid complications caused by scar tissueScar tissue
Scar tissue can refer to:*Granulation tissue, a product of healing in major wounds*The tissue of a scar*"Scar Tissue", a Red Hot Chili Peppers song*Scar Tissue , the autobiography of Anthony Kiedis, lead singer of the Red Hot Chili Peppers...
and the body’s repair mechanisms. Chronic PLC injuries are less likely to be amenable to repair due to complications from scar tissue and limb malalingment; these injuries will likely necessitate reconstruction. Knees in varus alignment and which have chronic injuries (evaluated by long leg standing radiographs) will require a staged procedure that starts with an opening wedge osteotomy
Osteotomy
An osteotomy is a surgical operation whereby a bone is cut to shorten, lengthen, or change its alignment. It is sometimes performed to correct a hallux valgus, or to straighten a bone that has healed crookedly following a fracture. It is also used to correct a coxa vara, genu valgum, and genu varum...
. This procedure lessens the constraint on the knee and prevents the reconstruction grafts from stretching out. If the patient still has instability, the PLC reconstruction will take place approximately 6 months later. MRI scans will be helpful in determining whether torn structures are amenable to repair or will require reconstruction with allografts.
The structures considered for potential reconstruction are the fibular collateral ligament, popliteus tendon, and popliteofemoral ligament. The FCL and/or popliteus tendon are only considered for acute repair when they are avulsed off bone and can be reattached anatomically with the knee in extension. The PFL can be repaired when it is torn directly off of the fibular head and the popliteus is still intact. Reconstruction is preferred when the ligaments/tendons have mid-substance tears or other tears not amenable to repair. Reconstruction of either the FCL or popliteus tendon is typically completed utilizing a patient’s hamstring (semitendinous) for a graft; however when reconstructing both the FCL and popliteus an Achilles tendon
Achilles tendon
The Achilles tendon , also known as the calcaneal tendon or the tendo calcaneus, is a tendon of the posterior leg. It serves to attach the plantaris, gastrocnemius and soleus muscles to the calcaneus bone.- Anatomy :The Achilles is the tendonous extension of 3 muscles in the lower leg:...
graft from a cadaver is preferred.
Acute Isolated Posterolateral Knee Injuries
Isolated injuries to the posterolateral knee are best repaired in an anatomic fashion by attempting to reestablish the previous location of the damaged structure. Typically damaged structures can be directly sutureSuture
Surgical suture is a medical device used to hold body tissues together after an injury or surgery. It generally consists of a needle with an attached length of thread. A number of different shapes, sizes, and thread materials have been developed over its millennia of history.-History:Through many...
d or anchored back to their bony attachments. The goal is to always achieve a stable and secure repair so that patients can initiate ROM exercises. Certain situations require more complicated repairs:
Femoral avulsions of the FCL or popliteus typically require a slightly more complex repair using a recess procedure in which stitches are placed through a bone tunnel and around the avulsed structure to proved further stabilization and return to range of motion exercises.
Avulsion fractures that occur at the fibular head or fibular styloid typically are caused by detachment of the popliteofibular ligament, direct arm of either the long or short heads of the biceps femoris or FCL. These fractures are best repaired with nonabsorbable suture or with wires. If the fracture is large enough, open fixation with surgical hardware may be required.
Midsubstance tears of the FCL or popliteus tendon are best treated with anatomic reconstructions.
Acute Combined Posterolateral Knee Injuries
Treatment for patients with combined grade III posterolateral injuries is quite similar to that of isolated PLC injuries. Repair or anatomic reconstruction of the posterolateral structures should be scheduled within 3 weeks of the initial injury. The other structures damaged should be reconstructed concurrently with the posterolateral structures so that the patient can readily return to a rehab program stressing range of motion exercises. This acts to prevent the development of arthrofibrosis (excessive scar tissue build up).Chronic Isolated Posterolateral Knee Injuries
Patients with chronic isolated posterolateral knee injuries that are in varus alignment will require a staged procedure that starts with an opening wedge osteotomy. Multiple studies agree that reconstruction of chronic grade III PLC injuries have significantly better outcomes than repairs; however, If MRI reveals repairable damage of some individual structures in the PLC, repairs can done in a similar fashion the method described above for acute posterolateral injuries. These structures which can be repaired include the biceps femoris and mid-third lateral capsular ligament. The vast majority of these patients will require reconstruction of the torn structures using an autograft or allograft to restore stability and function of the damaged structures. Anatomic (grafts placed in the exact attachment sites) allograft reconstruction of the FCL and/or popliteus tendon and popliteofibular ligament complex restore the static stabilizers of the posterolateral knee, which allows for early postoperative range of motion.Chronic Combined Posterolateral Knee Injuries
Similar to chronic isolated injuries, patients with chronic combined posterolateral knee injuries showing varus alignment will first require an opening wedge osteotomy as part of a staged procedure. With chronic combined PLC injuries the surgeon should treat the injury as if it was isolated with an anatomic reconstruction concurrent with a standard reconstruction of the accompanying ACL and/or PCL injuries. The key point here is that the multiligament reconstructions be done at the same time and not as a staged procedure. This will allow for early range of motion (ROM) exercises to begin and prevent the formation of arthrofibrosisArthrofibrosis
Arthrofibrosis is a complication of injury or trauma where an excessive scar tissue response leads to painful restriction of joint motion, with scar tissue forming within the joint and surrounding soft tissue spaces and persisting despite rehabilitation exercises and stretches...
in the joint. In addition, failing to address a chronic posterolateral knee injury when repairing a deficient ACL or PCL has been shown to cause increased forces of the graft leading to cruciate reconstruction graft stretching and/or failure.
Rehabilitation
Rehabilitation protocols for post-op patients with repaired or reconstructed posterolateral corner injuries focus on strengthening and achieving full range of motion. Similar to nonoperative treatments, the patient is non-weightbearing for 6 weeks followed by a return to partial weight-bearing on crutches. Range of motion exercises begin first at 1 to 2 days postoperatively, followed by progressive strength training. Patients can typically begin riding a stationary bike and using a quadriceps machine around 6 to 8 weeks, but isolated hamstring exercises should be avoided for a minimum of 4 months postoperatively. Patients can progress to leg pressLeg press
The leg press is a weight training exercise in which the individual pushes a weight or resistance away from them using their legs. The term leg press also refers to the apparatus used to perform this exercise...
es after 6 weeks, but the weight should be very light. Jogging
Jogging
Jogging is a form of trotting or running at a slow or leisurely pace. The main intention is to increase fitness with less stress on the body than from faster running.-Definition:...
and more aggressive strength training can begin around 4 – 6 months at the surgeon and physical therapists discretion. Patients should not be casted after surgery unless absolutely necessary.
Surgical Outcomes
A study by Geeslin and LaPrade indicated that patients reported positive outcomes in 94% of cases following a mix of repairs and reconstructions for with acute posterolateral knee injuries. Recent studies have reported failure rates between 37 and 40% for primary repairs of the main PLC structures Studies have shown that patients who undergo successful surgical repair of posterolateral knee injuries reported increased objective knee stability and better subjective outcomes than those who undergo reconstruction. A study by LaPrade et al showed that patients with isolated or combined PLC injuries have positive outcomes when they undergo anatomic reconstruction of the damaged structures, and there was no difference between groups that require an osteotomy versus those who do not. Patients reported significant increases in both knee stability and function following reconstruction. Anatomic techniques aim to restore normal function of the knee’s important static stabilizers and are recommended for patients with these types of injuries to provide the best outcomes.Complications
Follow-up studies by Levy et al. and Stannard at al. both examined failure rates for posterolateral corner repairs and reconstructions. Failure rates repairs were approximately 37 – 41% while reconstructions had a failure rate of 9%.Other less common surgical complications include deep vein thrombosis
Deep vein thrombosis
Deep vein thrombosis is the formation of a blood clot in a deep vein. Deep vein thrombosis commonly affects the leg veins or the deep veins of the pelvis. Occasionally the veins of the arm are affected...
(DVTs), infection, blood loss, and nerve/artery damage. The best way to avoid these complications is to preemptively treat them. DVTs are typically treated prophylactically with either aspirin
Aspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
or sequential compression device
Sequential compression device
Sequential compression device, abbreviated SCD, is an improved type of intermittent pneumatic compression system that includes inflatable compression sleeves and a characteristic pressure modulation in order to reduce risk of clot formation, such as deep vein thrombosis, in the legs of hospitalized...
s (SCDs). In high risk patients there may be a need for prophylactic administration of low molecular weight heparin
Low molecular weight heparin
In medicine, low-molecular-weight heparin is a class of medication used as an anticoagulant in diseases that feature thrombosis, as well as for prophylaxis in situations that lead to a high risk of thrombosis....
(LMWH). In addition, having a patient get out of bed and ambulate soon after surgery is a time honored way to prevent DVTs. Infection is typically controlled by administering 1 gram of the antibiotic cefazolin
Cefazolin
Cefazolin , also known as cefazoline or cephazolin, is a first-generation cephalosporin antibiotic.The drug is usually administrated by either intramuscular injection or intravenous infusion .-Indications:Cefazolin is mainly used to treat bacterial infections of the skin...
(Ancef) prior to surgery. Excessive blood loss and nerve/artery damage are rare occurrences in surgery and can usually be avoided with proper technique and diligence; however, the patient should be warned of these potential complications, especially in patients with severe injuries and scarring.