The knee allows for flexion, extension and rotation.
The cruciate ligaments are structures related to knee stability located at the centre of the joint. The anterior cruciate ligament (ACL), as well as the posterior (PCL) are intra-articular.
The ACL originates on the femur, on the postero-lateral portion of the inter-condyle and is inserted anteriorly into the tibia. The tibia insertion is more resistant than the femoral.
This ligament has two bands: the antero-medial and the postero-lateral, and its purpose is to resist the anterior dislocation of the tibia as well as medial knee rotation. When this ligament is ruptured, the tibia projects itself onto the femur.
The main functions of knee ligaments are stabilization, kinematics control and prevention of dislocations as well as abnormal rotations that may cause lesions to the joint surface.
The ligaments, such as tendons, are dense collagen bands with little cellular material, which respond to linear tensions. Unlike tendons, ligaments have not so many parallel fibres and an enhanced amount of elastin, being able to support more stretching without causing damage to its structure. ACL and PCL have viscoelastic properties, allowing them to disperse energy, regulate their length and distribute load.

The incidence of this kind of lesion has been increasing in women, children, teenagers and older adults. This happens due to involvement in sports in which sudden deceleration and displacement are possible. Women, due to anatomic and hormonal, among other pre-dispositions are more likely to suffer from ACL damage.

Treatment is performed by replacing the damaged ligament with a substitute graft which may be a section of the tendon or hamstrings, either belonging to the patient or alternatively taken from a corpse.
Direct suture of a broken ligament does not work properly, the purpose of surgery being the placement of the substitute graft at  the tension point of the original ligament. The graft may be set using screws, wires or pins.
Ligament rupture often produces meniscus lesions, reconstruction of the ligament being then required.

The doctor will indicate requirements, specific to each patient.

As in any surgery, various complications can occur, the most common being inability to completely extend the knee, which can be caused by arthrofibrosis, intercondylar cut scarring or knee immobilisation when flexed or infected.

After surgery, the patient will experience edema and knee pain, and should always use auxiliary walking equipment. A month and a half after the surgery, the equipment will no longer be needed or can partially be done away with, although walking on firm ground only is still advised.
Usually after two months the edema will have completely disappeared, as well as the pain.

Muscular recovery should be phased and progressive. Initially, exercises that strain the “neo-ligament” must not be undertaken.