Anterior cruciate ligament (ACL) sprains or tears are one of the most common types of knee injuries.

Players in sports such as football and basketball are more prone to these injuries due to the high demand on the joint through the play.

Some patients who injure their anterior cruciate ligament require surgery to fully recover their knee, but it isn’t always the case. The severity of the injury and your level of activity will determine if surgery is right for you.

Nearly half of anterior cruciate ligament injuries occur with other knee damage, such as articular cartilage and meniscus tears or injuries to the other ligaments. In general, anterior cruciate ligaments tend to tear completely instead of partially tearing.

The severity of the sprain, or injury, to the ligament can be plotted on a simple scale.

When the sprain is a grade 1, the ligament has sustained mild damage. It may have been slightly stretched, but it can keep the knee joint functioning normally and with stability.

When a sprain ventures into grade 2, the ligament becomes loose, often called a partial tear.

Grade 3 sprains are complete tears of the ligament, meaning the tissue is in two pieces. In this case, the joint is unstable and intervention is needed.

Many forces can cause the anterior cruciate ligament to become injured, such as:

  • Rapid direction changes
  • Sudden stopping
  • Slowing from a run
  • Incorrectly landing a jump
  • Direct impact or trauma

Unfortunately, female athletes in certain sports have higher incidences of ACL injuries. Differences in conditioning, muscle strength, and muscular control are often sites as reasons. In addition, pelvic and lower extremity alignment are possible causes, as are looser ligaments and the effects of estrogen on the relative properties of ligament tissue.

The most common symptoms of an ACL injury are a popping noise and your knee giving out under you. However, other symptoms are also possible with this injury. Pain is present along with swelling. In fact, the first 24 hours are a time of increased swelling in the joint, and it could resolve itself at this point. Returning to your sport or activity, though, will make the joint unstable and can cause further damage, such as tears to the meniscus, or cartilage, in your knee.

Other symptoms include:

  • Unable to complete full range of motion
  • Tenderness along the joint
  • Pain with walking

Your doctor will start with a physical examine and detailed history. You will talk about what symptoms you are feeling and what other medical issues you may have.

The physical examination is hands on, and your doctor will check all the structures of the knee in question. Often, they will be compared to structures on the other knee. Usually, close physical examination can determine the knee injury.

Radiological imaging tests may be prescribed as well. Plain x-rays will not usually show an injury to the anterior cruciate ligament, but they can show broken bones.

Usually, MRIs are better at visualizing the soft tissue, such as the ACL. However, MRIs aren’t strictly necessary to diagnose an anterior cruciate ligament sprain.

The treatment used for an ACL tear varies widely upon the individual. For instance, an athlete in a contact sport will probably need surgery to return to the playing field. Older adults who are not making such demands on their knees may be able to use only non-surgical treatments.


Unfortunately, a completely torn ACL will not heal without surgery. However, a nonsurgical approach could be useful for those who are poor surgery candidates or are not active. If the knee is stable overall, nonsurgical options may be right for you.

Bracing can be used to help support the instability in the joint. In addition, crutches can help to keep weight off the leg and allow the ACL to heal from milder strains.

Physical therapy is important, as well, and it is usually used after the initial swelling has subsided. Working with a therapist, you will be taught specific exercises to restore your range of motion and strengthen the muscles around your knee.

Most surgical treatments focus on rebuilding the ligament. Unfortunately, the ACL cannot simply be stitched back together. For the knee to regain its stability, the tissue needs to be reconstructed. This is usually performed with a tissue graft that acts as a scaffolding for a new ligament to grow on.

A graft can be obtained from a number of sources. One place is the patient’s own patellar tendon, or the tissue that runs between the patella and the tibia. In addition, the hamstring tendon that supports the back of the thigh is a possibility, and one of the tendons of the quadriceps, or the muscles of the thigh, can also be used. When these are not viable, a graft from a cadaver, called an allograft, is often used.

Each graft source has its own particular advantages and disadvantages. This is an important point of discussion between your surgeon and you to determine the best course.

The regrowth of the tendon takes time, and it is usually six months or more before an athlete can return to their sport following ACL reconstruction.

Although every patient is different, this procedure is usually performed with an arthroscope using small incision. The benefit of this is that it is less invasive, cause less pain, require less time in the hospital, and generally lead to quicker recovery.

In many cases, surgeons will wait to perform ACL surgery unless other ligaments are involved. This allowed for the inflammation to decrease and for some of the range of motion to return. If the surgery is performed too quickly, scar tissue, or arthrofibrosis, can form in the joint, and this could result in the loss of motion in the knee.

Regardless of your treatment approach, knee rehabilitation is vital in allowing you to return to your normal activities. Physical therapy after surgery will help your knee to strengthen and allow for complete range of motion.

When following surgery, physical therapy focuses first on returning motion to the knee and surrounding muscles. Following this is a strengthening program that helps to protect the reconstructed tissue.

Slowly, this strengthening increases the stress the ligament experiences. In the last phase of rehabilitation, the focus is on the functional exercises that will allow for a return to the athlete’s sport.


Your knee joint is made up of the juncture between three bones: the thighbone or femur, the shinbone or tibia, and the kneecap or patella. The kneecap is on the front of the joint to help protect the juncture of the other two bones.

Ligaments are the strong bands of tissue that connect bone to bone. In the knee, you have four primary ligaments that help hold the knee together and promote joint stability.

Collateral Ligaments
The sides of the knee are supported by these ligaments. On the inside of your knee is the medial collateral ligament while the lateral collateral ligament supports the outside. They are responsible for limiting side to side movement, and they prevent other unusual movements of the joint.

Cruciate Ligaments
These two ligaments are found inside the knee joint and cross to from an “X”. The anterior cruciate ligament is in the front of the joint while the posterior cruciate ligament supports the back. Back and forth movement of the joint is usually regulated by these bands of tissue.

The anterior cruciate ligament specifically keeps the tibia from sliding out from under the femur. It does this by diagonally crossing the middle of the knee, and it provides rotational stability, as well.

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