Lower Limb
Embryology
  Knee   Ankle  
      Anatomy
    Bones
    Ligaments
    Bursae
Radiology
Clinical Cases
     
LIGAMENTS

The ligaments of the knee can be broken up into two groups:
1) Intracapsular Ligaments
2) Extracapsular Ligaments

The intracapsular ligaments lie within the knee joint capsule and outside the synovial cavity, while the extracapsular ligaments lie outside the knee joint capsule.

INTRACAPSULAR LIGAMENTS

1) ANTERIOR CRUCIATE LIGAMENT (ACL)

The ACL arises from the anterior intercondylar area of the tibia. It then courses superiorly, posteriorly and laterally to insert on the posterior medial side of the lateral femoral condyle.

During extension of the knee the ACL is taut, preventing anterior displacement of the tibia in relation to the femur (or posterior displacement of the femur in relation to the tibia) and hyperextension of the knee. The ACL is lax when the knee is flexed. During extension of the knee when the ACL is most taut, it can be torn.

2) POSTERIOR CRUCIATE LIGAMENTS (PCL)

The PCL is the stronger of the two cruciate ligaments. It arises from the posterior intercondylar area of the tibia and courses superiorly, anteriorly and medially to insert on the lateral side of the medial femoral condyle.

The PCL is taut during flexion of the knee, preventing posterior displacement of the tibia in relation to the femur and hyperflexion of the knee. When walking downhill or up stairs, the PCL helps to stabilize the weight-bearing flexed knee.

Diagram taken from:  Netter, Frank H, MD.  Atlas of Human Anatomy.  ICON Learning Systems, New Jersey 1997.  Plate 475.
Diagram taken from: Netter, Frank H, MD. Atlas of Human Anatomy. ICON Learning Systems, New Jersey 1997. Plate 475.

3)MENISCI

The menisci are C shaped plates of fibrocartilage that sit between the femur and tibia. There are 2 menisci within each knee joint, known as the medial meniscus and lateral meniscus. In cross section, each meniscus appears as a wedge shaped structure with a thick, broad peripheral surface and a thin, pointed central surface. The menisci attach both anteriorly and posteriorly to the intercondylar eminence of the tibia forming the anterior and posterior horns of the menisci respectively. The menisci act as shock absorbers of the knee and help to lubricate the articular surfaces by spreading out synovial fluid.

Although the medial and lateral menisci share the same function, they differ in their attachments and relationships to other structures within the knee joint. The anterior horn of each menisci attaches anteriorly on the intercondylar eminence of the tibia. However, the anterior horn of the medial meniscus inserts on the intercondylar eminence anterior to the ACL attachment on the tibia, while the anterior horn of the lateral meniscus attaches to the intercondylar eminence posterior to the ACL attachment on the tibia.

Diagram taken from:  Netter, Frank H, MD.  Atlas of Human Anatomy.  ICON Learning Systems, New Jersey 1997.  Plate 474.
Diagram taken from: Netter, Frank H, MD. Atlas of Human Anatomy. ICON Learning Systems, New Jersey 1997. Plate 474.

Another important distinction between the medial and lateral meniscus is their relationship to the collateral ligaments. The medial meniscus is firmly attached to the medial collateral ligament. Since the medial meniscus is firmly joined to the medial collateral ligament, it may tear upon twisting of the ligament. In contrast, the lateral meniscus is separated from the lateral collateral ligament by the tendon of the popliteus muscle. Consequently, the lateral meniscus is less firmly attached, more mobile and is less frequently torn.

4) TRANSVERSE LIGAMENT

The transcvers ligament bind the anterior horns of the medial and lateral menisci.


EXTRACAPSULAR LIGAMENTS

1) MEDIAL (TIBIAL) COLLATERAL LIGAMENT

The medial collateral ligament runs from the medial epicondyle of the femur to the medial condyle of the tibia. It attaches to the medial meniscus at its midpoint (**see section on medial meniscus for clinical importance). The medial collateral ligament limits abduction and extension of the leg.

2) LATERAL (FIBULAR) COLLATERAL LIGAMENT

The lateral collateral ligament runs from the lateral epicondyle of the femur to the lateral surface of the head of the fibula. It does not attach to the tibia. The tendon of the popliteus muscle runs deep to the ligament, separating the lateral collateral ligament from the lateral meniscus. In addition, the tendon of the biceps femoris is split in half by the ligament. The lateral collateral ligament limits adduction and extension of the leg.

Diagram taken from:  Netter, Frank H, MD.  Atlas of Human Anatomy.  ICON Learning Systems, New Jersey 1997.  Plate 475.
Diagram taken from: Netter, Frank H, MD. Atlas of Human Anatomy. ICON Learning Systems, New Jersey 1997. Plate 475.

3) PATELLAR LIGAMENT

The patellar ligament is an extension of the quadriceps femoris tendon that runs from the apex of the patella to the tuberosity of the tibia.

4) ARCUATE POPLITEAL LIGAMENT

The arcuate popliteal ligament is a "Y" shaped ligament that runs from the posterior surface of the fibula, over the tendon of the popliteus muscle, to the posterior surface of the knee joint. This ligament fuses with the articular capsule and functions to strengthen the capsule posteriorly.

5) OBLIQUE POPLITEAL LIGAMENT

The oblique popliteal ligament is an extension of the semimembranosus tendon that runs from the medial tibial condyle to the posterior surface of the knee joint. This ligament serves to strengthen the fibrous capsule of the knee posteriorly, similar to the arcuate popliteal ligament.



Home

UCONN Health Center