Knee Ligaments: What are they? Structure, Function and Linked Injuries

They surround the knee joint, offer stability by limiting movements, and protect the joint capsule with the menisci and several bursas.

Intracapsular structure

A pair of crossed ligaments stabilize the knee. The anterior cruciate ligament (ACL) extends from the lateral condyle of the femur to the anterior intercondylar area.

The cruciate ligaments (also cruciform ligaments) are pairs of ligaments arranged like a letter X.

They occur in various joints of the body, such as the knee. Like the ropes in a ladder Jacob, the crossed ligaments stabilize the joint and allow an extensive range of motion.

The anterior cruciate ligament (ACL):

It is one of a pair of crossed ligaments (the other is the posterior cruciate ligament) in the human knee. The two ligaments are also called cruciform ligaments since they are arranged in a cross formation.

The articulation of the quadrupedal knee (analogous to the knee) is also known as the cranial cruciate ligament, depending on its anatomical position.

The anterior cruciate ligament is one of the knee’s four major ligaments, providing 85% of the restraining force to the anterior tibial displacement at 30 degrees and 90 degrees of knee flexion.


It is critically important because it prevents the tibia from being pushed too far forward concerning the femur. It is often torn during twisting or bending of the knee.

The anterior cruciate ligament originates from deep in the notch of the distal femur. Its proximal fibers fan out along the medial wall of the lateral femoral condyle.

There are two bundles of the anterior cruciate ligament: the anteromedial and the posterolateral, named according to the place where the bundles are inserted in the tibial plateau. (The tibia plateau is a critical region that supports weight in the upper extremity of the tibia).

The anterior cruciate ligament adheres to the tibia’s intercondylar eminence, where it is mixed with the anterior horn of the lateral meniscus.

These accessories allow the anterior cruciate ligament to resist anterior translation and medial rotation of the tibia about the femur.

The posterior cruciate ligament:

The posterior cruciate ligament is one of the knee’s four major ligaments. It extends from the medial condyle of the femur to the rear intercondylar area.

It connects the posterior intercondylar area of ​​the tibia with the medial condyle of the femur. This configuration allows the posterior cruciate ligament to resist the forces that push the tibia posteriorly about the femur.

The posterior cruciate ligament is intracapsular, and the anterior cruciate ligament (ACL) is located inside the knee joint.

Both are isolated from the synovial cavity filled with fluid, with the synovial membrane wrapped around them. The posterior cruciate ligament is named after the rear portion of the tibia.

The posterior cruciate ligament is located inside the knee joint, stabilizing the articulated bones, particularly the femur and the tibia, during movement.

It originates at the lateral border of the medial femoral condyle, and the roof of the interchondral notch is stretched, at a posterior and lateral angle, towards the rear part of the tibia just below its articular surface.

Although each posterior cruciate ligament is a unified unit, they are described as separate anterolateral and posteromedial sections depending on the place of insertion and function of each section.

During movement of the knee joint, the posterior cruciate ligament rotates so that the anterolateral section is stretched in knee flexion but not in knee extension, and the posteromedial bundle stretches in extension rather than flexion.

The function of the posterior cruciate ligament is to prevent the femur from sliding off the anterior edge of the tibia and prevent the tibia from moving backward from the femur. The posterior cruciate ligament is inside the knee.

Ligaments are full bands of tissue that connect bones. The posterior cruciate ligament connects the femur to the tibia, similar to the anterior cruciate ligament.

The injury to this ligament is uncommon, but it can occur directly from a forced trauma to the ligament. This ligament prevents the posterior displacement of the tibia concerning the femur.

The transverse ligament:

The transverse or anterior meniscomeniscal ligament is a ligament in the knee joint that connects the anterior convex edge of the lateral meniscus with the anterior end of the medial meniscus.

It extends from the lateral meniscus to the medial meniscus. Pass in front of the meniscus. It is divided into several strips in ten percent of the subjects, and its thickness varies considerably in different subjects.

When the knee is extended, the ligament prevents the anterior meniscus horns from moving forward, and the condylar surfaces of the femur and tibia exert pressure on the menisci.

It has a restrictive effect on the anteroposterior excursion of the anterior horn of the medial meniscus in lower degrees of knee flexion.

It is divided into several strips in 10% of cases. The two menisci are attached anteriorly by the ligament.

Posterior meniscofemoral ligament:

The posterior meniscofemoral ligament (also known as the Wrisberg ligament) is a small fibrous band of the knee joint.

It adheres to the posterior area of ​​the lateral meniscus and crosses superiorly and medially behind the posterior cruciate ligament to join the medial condyle of the femur.

It is formed with articulatio meniscolateralis anterior articulatio mesicofemoralis, which is the upper floor of the genus articulatio. It flexes and functionally extends as a hinge joint with a front axle.

The posterior meniscofemoral ligament is more commonly present (30%); both ligaments are present less frequently.

Anterior meniscofemoral ligament:

The anterior meniscofemoral ligament (Humphrey’s ligament) is a small fibrous band of the knee joint.

It arises from the posterior horn of the lateral meniscus. It passes superiorly and medially in front of the posterior cruciate ligament to join the lateral surface of the medial condyle of the femur.

It can be confused with the posterior cruciate ligament during arthroscopy. In this situation, a pull on the ligament can be used while watching the movement of the lateral meniscus to differentiate them.

The posterior and anterior meniscofemoral ligaments extend from the posterior horn of the lateral meniscus to the medial femoral condyle. They pass posteriorly behind the posterior cruciate ligament.

Coronary ligament of the knee:

The coronary ligaments of the knee (also known as meniscotibial ligaments ) are portions of the joint capsule that connect the inferior edges of the fibrocartilaginous menisci to the periphery of the tibial plateaus.

The coronary ligaments of the knee are continuous with the joint capsule and the menisci. The coronary ligaments function to connect parts of the outer and lower edges of the medial and lateral menisci to the joint capsule of the knee.

The medial meniscus also has tight junctions laterally to the intercondylar area of ​​the tibia and medially to the tibial collateral ligament.

The lateral meniscus has tight junctions medially to the intercondylar area through the ends of the meniscus and posteromedially through the posterior meniscofemoral ligament, which joins the posterior extremity meniscus with the posterior cruciate ligament and the medial femoral condyle.

The lateral meniscus is not directly connected to the collateral ligament of the fibula and, therefore, is more mobile than the internal meniscus.

The meniscotibial (or “coronary”) ligaments extend from the lower edges of the menses to the periphery of the tibial plateaus.

Extracapsular structure

The patellar ligament:

The patellar ligament is the distal portion of the common tendon of the quadriceps femoris, which connects the patella to the tuberosity of the tibia.

Also sometimes called patellar tendon because there is no defined separation between the quadriceps tendon (which surrounds the patella) and the area that connects the patella to the tibia.

This very strong and flat ligament originates in the apex of the patella distally and the adjacent margins of the patella and the rough depression in its posterior surface; then, it is inserted into the tuberosity of the tibia; Its superficial fibers are continuous on the frontal part of the patella with those of the tendon of the quadriceps femoris.

It helps give the kneecap its mechanical levering ability and functions as a cap for the femoral condyles. Laterally and medially to the patellar ligament, the lateral and medial retinacula connect the fibers of the vasti lateralis and medialis muscles with the tibia.

Some fibers of the iliotibial tract radiate towards the lateral retinaculum, and the internal retinaculum receives some transverse fibers that arise in the medial femoral epicondyle. It is approximately 4.5 cm long in adults (3 to 6 cm).

The medial and lateral portions of the quadriceps tendon descend on both sides of the patella to be inserted at the upper end of the tibia on each side of the tuberosity; these portions are fused in the capsule, as indicated above, forming the medial and lateral patellar retinacula.

The posterior surface of the patellar ligament is separated from the synovial membrane of the joint by a large pad of infrapatellar fat and the tibia by a bag.

The medial collateral ligament:

The medial collateral ligament or tibial collateral ligament is one of the four major ligaments of the knee.

It is on the knee joint’s medial (internal) side in humans and other primates. Its primary function is to resist the valgus forces in the knee.

It is a broad, flat membranous band located slightly posteriorly on the medial side of the knee joint.

It is attached proximally to the medial epicondyle of the femur immediately below the adductor tubercle, below the medial condyle of the tibia, and the medial surface of your body. It comprises three groups of fibers, one that extends between the two bones and two fused with the medial meniscus.

The medial collateral ligament is partially covered by the pes anserine or anserine (goose’s foot), and the semimembranous tendon passes underneath. It protects the medial side of the knee so that it is not bent by a tension applied to the lateral side of the knee (a force in the valgus).

Resists the forces that would push the knee medially, otherwise resulting in a valgus deformity.

The posterior part of the ligament fibers are short and lean backwards as they descend; they are inserted into the tibia above the groove for the semimembranosus muscle.

The anterior part of the ligament is a flattened band, about 10 centimeters long, that leans forward as it descends. It is inserted into the medial surface of the body of the tibia about 2.5 centimeters below the level of the condyle.

Crossing the upper part of the lower part of the medial collateral ligament is the anserinus foot, the united tendons of the sartorius, gracilis, and semitendinosus muscles; a bursa comes between the two.

The deep surface of the medial collateral ligament covers the inferior medial genital vessels and the nerve and the anterior portion of the semimembranosus muscle tendon, to which a few fibers connect it; It is intimately attached the medial meniscus.

The lateral collateral ligament:

The fibular collateral ligament (long lateral ligament or collateral lateral ligament) is a ligament located on the lateral (external) side of the knee. Therefore, it belongs to the knee’s extrinsic ligaments and the posterolateral corner of the knee.

Rounded, narrower, and less broad than the medial collateral ligament, the collateral ligament of the fibula extends obliquely downward and backward from the lateral epicondyle of the femur upwards to the head of the inferior fibula.

It extends from the lateral epicondyle of the femur to the head of the fibula. It is separated from both the joint capsule and the lateral meniscus. Protects the lateral side of an internal bending force (a varus force).

It is not fused with either the capsular ligament or the lateral meniscus, unlike the medial collateral ligament. Because of this, the lateral collateral ligament is more flexible than its medial counterpart and, therefore, less susceptible to injury.

Both collateral ligaments are tense when the knee joint is in extension. With the knee flexion, the radius of curvature of the condyles decreases, and the origin and insertions of the ligaments approach, which makes them lax.

The ligament pair thus stabilizes the knee joint in the coronal plane. Therefore, damage and rupture of these ligaments can be diagnosed by examination of the mediolateral (lateral) stability of the knee.

Immediately below its origin is the groove for the popliteus tendon.

Most of its lateral surface is covered by the tendon of the biceps femoris; however, the tendon is divided into its insertion into two parts, separated by the ligament.

The popliteus tendon, inferior lateral genital vessels, and the nerve are deep in the ligament.

The anterolateral ligament:

The anterolateral ligament is a ligament on the lateral aspect of the human knee, anterior to the collateral ligament of the fibula. It is located in front of the lateral collateral ligament.

Perhaps the oldest description of the anterolateral ligament was written by the French surgeon Paul Segond in 1879. He described a ligamentous structure between the lateral femur and the tibia.

Claes and Bellemans (2013) found that the anterolateral ligament originates in the lateral epicondyle of the femur and inserts into the anterolateral aspect of the proximal tibia. However, Vincent et al . (2012) reported the origin of the lateral femoral condyle.

Finally, there are two ligaments on the dorsal side of the knee. The oblique popliteal ligament is a radiation of the semimembranous tendon on the medial side, from where it is directed laterally and proximally.

The arcuate popliteal ligament originates at the apex of the head of the fibula to stretch proximally, crosses the popliteus muscle tendon, and passes into the capsule.

Oblique popliteal ligament:

The oblique popliteal ligament (posterior ligament) is a broad, flat, and fibrous band formed by fascicles separated by openings for the passage of vessels and nerves.

It is attached to the upper margin of the intercondyloid fossa and the posterior surface of the femur near the joint margins of the condyles and below the posterior margin of the head of the tibia.

Superficial to the central part of the ligament is a substantial bundle derived from the semimembranosus tendon and which passes from the back of the medial condyle of the tibia obliquely upwards laterally to the posterior part of the lateral condyle of the femur.

The oblique popliteal ligament is part of the floor of the popliteal fossa, and the popliteal artery rests on it.

It is perforated by the posterior division of the obturator nerve, as well as the central genital nerve and vessels.

Arched popliteal ligament:

The arcuate popliteal ligament is an extracapsular ligament of the knee. It has a Y shape and is attached to the posterior part of the head of the fibula.

He goes to his two insertions; the medial passes through the popliteal muscle and combines with the oblique popliteal ligament, lateral to the lateral epicondyle of the femur, and then mixes with the lateral head of the gastrocnemius muscle.

Broken ligament injuries in the knee

If you think you have a broken ligament in your knee, you are not alone. Injuries to the knee, such as broken ligaments, are prevalent, especially if you are involved in sports.

In some cases, the next step to take if you have a torn ligament is surgery. However, many knee injuries can be improved without surgery; you need to rest your knee and perform simple treatments that your doctor will recommend.

There are two sets of ligaments in your knee; these are there to keep your knee stable. An injury to one of these ligaments can cause instability, pain, and swelling. You can hear or feel a snap when the damage occurs.

Lesions of the collateral ligament:

This affects the medial collateral ligament on the inner side of the knee and the lateral collateral ligament on the outside of the knee. These ligaments reduce the amount of side-to-side movement the knee has. You can twist or break any ligaments if your lower leg experiences outward force.

Injuries of the cruciate ligament:

His posterior cruciate ligament and anterior cruciate ligament form a cross inside his knee. These help control the movement of your knees back and forth.

Lesions are more likely to occur in these ligaments when the knee is suddenly twisted. The injuries to the anterior cruciate ligament are the most serious of all the ligament injuries in the knee.

If you have injured one or more of the ligaments in your knee, your doctor will examine it and then evaluate the injury according to the severity of the damage. The qualifications are the following:

  • Grade 1: a stretch of the ligament without a tear.
  • Grade 2: a partial tear.
  • Grade 3: a complete tear.