Injuries to the anterior cruciate ligament (ACL) (Anterior Cruciate Ligament (ACL) Injuries)

The rupture, or stretch, of the anterior cruciate ligament is one of the most common injuries to the knee.

Athletes who play sports with high physical demand, such as football, football and basketball, are more likely to injure the anterior cruciate ligaments.

When the anterior cruciate ligament is injured, there is a great chance that a surgical intervention will be necessary to restore knee function. It will depend on several factors, including: the severity of the injury and the patient’s activity level.


The knee joint is formed by the meeting of three bones: the thigh bone (femur), the leg bone (tibia) and the patella (patella). The kneecap is in front of the joint to protect it.

The bones are connected to each other by means of ligaments. There are four main ligaments in the knee. They act as resistant fibers that hold the bones together and the knee stable.

Collateral ligaments

They are located on both sides of the knees. The medial collateral ligament is located on the inside and the lateral collateral ligament on the outside. They control the lateral movements of the knee and prevent you from making improper movements.

Cruciate ligaments

They are found inside the knee joint. They cross forming an X; the anterior cruciate ligament is in the front, and the posterior cruciate ligament is in the back. The cruciate ligaments control the movement of the knee back and forth.

The anterior cruciate ligament crosses longitudinally the center of the knee. It prevents the tibia from moving in front of the femur, in addition to providing rotational stability to the knee.

Anatomy of normal knee, frontal view


In approximately half of the injuries of the anterior cruciate ligament, there are associated injuries, such as: damage to articular cartilage, meniscus or other ligaments.

Ligament injuries are called “stretches” and are classified according to a severity scale.

Grade 1 strains. In a grade 1 stretch, the ligament is slightly damaged. He was slightly stretched, but still manages to keep his knee joint stable.

Grade 2 strains. In a grade 2 stretch, the ligament is stretched to the point of loosening. It is often called a partial ligament rupture.

Grade 3 strains. This type of stretch is often called a total ligament tear. The ligament is separated into two pieces, and the knee joint is unstable.

Partial ruptures of the anterior cruciate ligament are rare; in most ACL injuries, total or practically total rupture occurs.


The anterior cruciate ligament can be injured in several ways:

  • Quick change of direction
  • Stop at once
  • Reduce speed during a run
  • Supporting your feet incorrectly after a jump
  • Direct contact or collision, such as a football tackle

Several studies have shown that female athletes have a higher incidence of ACL injuries than male athletes in certain sports. The proposed explanations suggest that this difference is due to differences in physical conditioning, muscle strength and neuromuscular control. Other suggested causes include differences in the alignment of the pelvis with the lower limb (leg), greater laxity of the ligaments and effects of estrogen on the properties of the ligaments.


When the anterior cruciate ligament is injured, it is usually possible to hear a click and feel the knee move. Other typical symptoms include:

  • Pain and swelling. Within 24 hours after the injury, the knee will swell. If left untreated, the swelling and pain go away on their own. But if you try to resume physical activity, your knee is likely to be unstable, which can cause further damage to the cushioning cartilage (meniscus) of the knee.
  • Reduced range of motion
  • Sensitivity along the joint line
  • Discomfort when walking

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Medical exam

Physical examination and patient history

During the first consultation, the doctor will discuss the symptoms and medical history.

On physical examination, he will examine all structures of the injured knee and compare them with those of the contralateral (healthy) knee. Most ligament injuries can be diagnosed by careful physical examination of the knee.

Imaging exams

Other tests that can help the doctor confirm the diagnosis are:

Xrays. Although radiographs may not reveal lesions of the anterior cruciate ligament, they can show whether the lesion is associated with fractures.

Magnetic resonance imaging (MRI). This exam provides better images of the soft tissues, such as the anterior cruciate ligament. However, an MRI is usually not necessary to complete the diagnosis of a ruptured ACL.


The treatment for ruptured ACL rupture will vary according to the needs of each patient. For example, young athletes involved in agility sports are likely to need surgery to return to the sport. Less active people, usually older people, may be able to resume calmer lifestyles without surgery.

Non-surgical treatment

The ruptured ACL does not heal without surgery. But non-surgical treatment can be effective for patients who are older, or who have a very low level of physical activity. If the stability of the knee as a whole is preserved, the doctor may recommend simple non-surgical options.

Orthoses. The doctor may recommend the use of an orthosis to protect the knee from instability. To give additional protection to the knee, it is also possible to use crutches to prevent the body weight from being supported on the injured knee.

Physiotherapy. As the swelling subsides, a cautious rehabilitation program will begin. Specific exercises will restore your knee functions and strengthen the muscles that surround the knee.

Surgical treatment

Ligament reconstruction. Most ACL tears cannot be sutured (joined with stitches). To surgically repair the ACL and restore knee stability, the ligament needs to be reconstructed. The doctor will replace the torn ligament with a tissue graft. This graft acts as a platform for the growth of a new ligament.

Grafts can be obtained from several sources. They are usually removed from the patellar tendon, which extends between the patella and the leg bone. The tendons on the back of the thigh are a common source of grafts. Sometimes a quadriceps tendon, which runs down the thigh from the kneecap, is used. Finally, a cadaver graft (allograft) can also be used.

All graft sources have their advantages and disadvantages. The graft options should be discussed with the orthopedic surgeon to determine which is the best.

As it takes time for the ligament to incorporate, it may take an athlete six months or more to return to sports after surgery.

Procedure. Surgery to reconstruct the anterior cruciate ligament is performed by inserting an arthroscope through small cuts. Arthroscopic surgery is less invasive. The benefits of less invasive techniques include less pain from surgery, less hospital stay and shorter recovery times.

Unless it is the treatment for an injury associated with ligament injuries, ACL reconstruction is not usually performed immediately. Inflammation is expected to cease and movements to return before surgery. The very early performance of ACL reconstruction greatly increases the risk of arthrofibrosis, or scar formation in the joint, which carries the risk of loss of knee movements.

See a more in-depth discussion of ACL injuries and surgical treatment at: ACL Injury: Does It Require Surgery?


Regardless of whether treatment involves surgery, rehabilitation plays a vital role in resuming day-to-day activities. A physical therapy program will help to regain strength and knee movements.

In cases of surgery, physiotherapy will focus first on recovering the movements of the joint and the muscles around it. It will then be followed by a strengthening program designed to protect the new ligament. Strengthening gradually increases the effort in the ligament regions. The final phase of rehabilitation is aimed at functional return, determined according to the athlete’s sport.


by Abdullah Sam
I’m a teacher, researcher and writer. I write about study subjects to improve the learning of college and university students. I write top Quality study notes Mostly, Tech, Games, Education, And Solutions/Tips and Tricks. I am a person who helps students to acquire knowledge, competence or virtue.

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