ANATOMY REVIEW
Coronal Mid1. Medial Femoral Condyle
2. Medial Tibial Plateau
3. Lateral Femoral Condyle
4. Lateral Tibial Plateau
5. Medial Collateral Ligament
6. Medial Meniscus (body)
7. Lateral Meniscus (body)
8. Anterior Cruciate Ligament (ACL)
9. Posterior Cruciate Ligament (PCL)
10. Ilial Tibial Band
Coronal Mid-Anterior1. Medial Femoral Condyle
2. Medial Tibial Plateau
3. Lateral Femoral Condyle
4. Lateral Tibial Plateau
5. Medial Collateral Ligament
6. Ilial Tibial Band
Coronal Posterior1. Medial Femoral Condyle
2. Medial Tibial Plateau
3. Lateral Femoral Condyle
4. Lateral Tibial Plateau
5. Fibular/Lateral Collateral Ligament (LCL)
6. Biceps Femoris Muscle
7. Gastrocnemious Muscle - Lateral Head
8. Gastrocnemious Muscle - Medial Head
9. Semimembranosis Muscle
10. Sartorius Muscle
A : Patella
B : Medial femoral condyle
C : Medial tibial condyle
D : Joint line
E : Tibial tuberosity
F : Head of fibula
Posterior Cruciate Anatomy
An understanding of posterior cruciate ligament (PCL) anatomy helps explain why PCL injuries are so different from anterior cruciate ligament (ACL) injuries. The PCL, unlike the ACL, is an extrasynovial structure. It attaches to the lateral side of the medial femoral condyle. The tibial attachment begins 1 cm below the tibial plateau on the posterior surface of the proximal tibia.
The PCL is larger and stronger than the ACL (1). It consists of a large anterolateral and a smaller posteromedial bundle. Its orientation is from anterior, at the femoral attachment, to posterior, at the tibial attachment (figure A). This orientation fits the ligament's function: preventing posterior subluxation of the tibia.
A ruptured PCL will allow the tibia to assume a more posterior position relative to the femur if a posterior force is applied to the tibia. When the PCL is torn, the extensor mechanism, including the patella and the patellar tendon, forcefully holds the tibia in a reduced position, which results in increased patellofemoral pressure (2). Increased patellofemoral loading is also caused by a vector change resulting from posterior tibial displacement. This may explain complaints of patellofemoral pain in patients who have PCL-deficient knees
Fibular Collateral Ligament (FCL)
The fibular collateral ligament is a short (5cm) cord extending from the lateral epicondyle of the femur to the lateral surface of the head of the fibula. The FCL and capsule (not shown here) are seperated from the lateral meniscus by The tendon of popliteus .
The FCL fuses with the fibrous capsule of the knee joint superiorly.
The FCL (and ~nesg/tutorials/knee/text/tibial1.html"TCL) prevent disruption of the sides of the knee joint. They are stretched in extension (rotation prevented) and are slack in flexion (rotation can occur). The FCL is very strong and not commonly torn although there may be partial tears of the distal end of the ligament. Complete FCL tear is associated with injury to the common peroneal (fibular) nerve.
Tibial Collateral Ligament
The tibial collateral ligament extends from the medial epicondyle of the femur to the medial condyle of the medial surface of the tibia. The TCL is attached firmly to the capsule, and the capsule is firmly attached to the medial meniscus.
The TCL (and ~nesg/tutorials/knee/text/fibrous1.html"FCL) prevent disruption of the sides of the knee joint.
They are stretched in extension, preventing rotation while being slack in flexion and allowing rotation in this position. The attachment of the TCL to the medial meniscus results in associated injuries. For example TCL rupture is associated with ~nesg/tutorials/knee/text/medial1.html"medial meniscus and ~nesg/tutorials/knee/text/anterior1.html"anterior cruciate ligament tears.
Oblique Popliteal Ligament
The back of the fibrous capsule is reinforced centrally by the oblique popliteal ligament .
This is an extension of the semimembranosus tendon and passes from the medial condyle of the tibia superolaterally to the posterior fibrous capsule.
Arcuate Popliteal Ligament
The arcuate popliteal ligament is shown on the left.
It is Y shaped, arching over popliteus , the stem arising from the head of the fibula and the arms spreading over the posterior surface of the knee joint inserting into the intercondylar area of the tibia and the posterior aspect of the lateral epicondyle of the femur.
Anterior Cruciate Ligaments (ACL)
The Anterior Cruciate Ligament arises from the anterior aspect of the intercondylar area of the tibia, posterior to the attachment of the medial meniscus. It extends posteriorly, laterally and superiorly to attach to the posterior part of the medial side of the lateral femoral condyle. The ACL is slack in flexion and taut in extension. However at 90 degrees flexion it becomes taut again. The ACL prevents posterior displacement of the femur on the tibia
Posterior Cruciate Ligament(PCL)
The Posterior Cruciate Ligament passes inferior to the posterior meniscofemoral ligament . It arises from the posterior part of the intercondylar area of the tibia and passes superiorly and anteriorly medial to the ACL to attach to the anterior part of the lateral surface of the medial femoral condyle. It is stronger than the ~nesg/tutorials/knee/text/anterior1.html"ACL, it tightens during knee flexion and prevents anterior displacement of the femur on the tibia or posterior displacement of the tibia. The PCL helps to stabilise the weight bearing flexed knee, for example, when walking downhill, or up stairs.
Synovial Capsule and Bursae
The synovial capsule is the largest joint space in the body and lines the fibrous capsule. Four bursae communicate with the synovial cavity of the knee joint.
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The Suprapatellar bursa can be seen in the lateral view shown alongside. It lies superiorly between femur and tendon of quadricep femoris. The prepatellar bursa, (which does not communicate with the synovial cavity) is also shown.
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Synovial Capsule and Bursae
The Posterior view shows :-
The Popliteus bursa , lies between popliteal tendon and lateral condyle of the tibia. The Semimembranosus bursa , is related to distal attachment of semimembranosus muscle and lies between the medial head of gastrocnemius and semimembranosus tendon.
The Gastocnemius bursa , is found deep to the proximal attachment of the medial head of gastronemius muscle.
Menisci
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The superior surfaces are concave for articulation with the femoral condyles. The menisci are fibrocartilaginous crescentic-shaped structures which are firmly attached to the intercondylar area of the tibia.
~nesg/tutorials/knee/text/lateral1.html"The Lateral Meniscus
~nesg/tutorials/knee/text/medial1.html"The Medial Meniscus
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The image above shows an axial section through the tibia and fibula.
The yellow line shows the approximate position of the coronal MR slice on the left
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Lateral Meniscus
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The lateral meniscus is smaller and more mobile than the medial meniscus and is almost circular in appearance. It is separated from the fibular colateral ligament ~nesg/tutorials/knee/text/fibrous1.html"(FCL) and capsule (not shown here) by the tendon of popliteus . The superior part of the popliteus tendon is extracapsular, it enters the capsule through a slit strengthened by the ~nesg/tutorials/knee/text/arcuate1.html"arcuate popliteal ligament the inferior section shown here is intracapsular. The posterior meniscofemoral ligament is a strong tendinous slip joining the lateral meniscus to the ~nesg/tutorials/knee/text/posterior1.html"posterior cruciate ligament .
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Medial Meniscus
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The medial meniscus is broader posteriorly than anteriorly. It is firmly adherent (via the capsule) to the deep surface of the tibial collateral ligament ~nesg/tutorials/knee/text/tibial1.html"(TCL).
Medial meniscus injury is 20 times more common than lateral meniscal injury. Injury usually results from a twisting strain with the knee in flexion. Because of the attachment to the ~nesg/tutorials/knee/text/tibial1.html"TCL , twisting strains of this ligament may be associated with medial meniscus tear. Knee locking occurs when a portion of the torn cartlidge is displaced and becomes lodged between tibial and femoral condyles.
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Joint Stability
Stability depends on the strength of the surrounding muscles and ligaments, particularly muscles. The most important is quadriceps femoris, consisting of :
A : Rectus femoris
B : Vastus medialis
C : Vastus lateralis
and the Vastus Intermedius (which is hidden by the other three muscles).
The inferior fibres of vastus medialis and lateralis are particularly important.
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see also knee anatomy
