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Anterior Cruciate Ligament (ACL) Surgery

Doctors Prepare for ACL SurgeryPrior to ACL Surgery

The anterior cruciate ligament (ACL) is one of the four major ligaments of the knee. It is an essential ligament that gives the knee stability. An ACL injury may range from mild, such as small tears, to severe, in which the ligament is completely torn. ACL surgery reconstructs a torn ACL and brings the knee back to full function.

Tearing the ACL is one of the most common knee injuries. More than 100,000 ACL tears occur in the U.S. every year.

The ACL helps stabilize the knee when turning or planting the body. Most ACL injuries take place during sports when a person is cutting, pivoting, sidestepping or lands abruptly. Downhill skiing, football, soccer, basketball and gymnastics are some of the sports in which ACL injuries commonly occur. These injuries usually do not involve knee contact and take place at low speed.

And, that is the ligament you don’t want injured. For starters, it is the one knee ligament that cannot heal on its own. In addition, it can’t be stitched back together. Women are more likely to suffer an ACL injury than men and ACL injuries are associated with team sports like football, volleyball and soccer.

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Watch a recap of Dr. Walt Lowe performing an ACL reconstruction live on Twitter »

Symptoms of a Torn ACL

Immediately after an ACL tear, a person usually:

  • hears a loud popping sound,
  • experiences pain and swelling,
  • says that the knee feels unstable or "wobbly."

Within a few hours, patients often have:

  • severe knee swelling,
  • a loss of range of motion,
  • pain or tenderness and
  • discomfort while walking.
If you are experiencing all or some of these symptoms, you should be evaluated by a knee specialist.

Diagnosis of Torn ACL

If you think you may have an ACL injury, you should be examined as soon as possible. In the examination, the doctor will:

  • Ask you to describe how the injury occurred
  • Examine the injured knee and check it for swelling and bruising
  • Check for areas of tenderness and signs of leaking knee joint fluid
  • Check the knee's stability and determine if any other ligaments besides the ACL are involved in the injury

The doctor may order:

  • A test to assess the ACL's stability and strength. These tests include the Lachman test, the pivot-shift test and the anterior drawer test.
  • X-rays to look for any possible fractures or a magnetic resonance imaging (MRI) scan to view the CL and check the extent of the injury.

Treatment Options for a Torn ACL

When it comes to ACL reconstruction, one size does not fit all.

You have to consider injury to surrounding tissue, how active the patient plans to be, how the patient might respond to a rigorous rehabilitation program as well as a host of other issues.

Nonsurgical Treatment

In nonsurgical treatment, a program of physical therapy and rehabilitation can restore the knee to close to its pre-injury state. People with less active lifestyles, as well as children, may opt for rehabilitation alone, which can compensate for the injury by building up the knee.

Depending on the patient’s goal, rest and physical therapy may be sufficient. An example of this would be a person who sustained the injury in a fall and does not plan to participate in sporting activities in the future. Athletes and people whose jobs involve demanding physical activities may require ACL surgery and more aggressive therapy.

Surgical ACL Reconstruction

Others – particularly athletes – may chose physical therapy and surgery, which often involves reconstructing the ACL with tissue taken from the patient’s kneecap or hamstring. Sometimes, tissue is harvested from a cadaver.

ACL surgery replaces a torn ACL with a tissue graft to restore the knee's function after an injury. The surgery is minimally invasive and performed arthroscopically.

First, a surgeon removes the torn ligament from the knee. The surgeon then inserts the graft through a hole created by a single hole punch.

The goal of ACL surgery is to create a stable knee and restore the function of the torn ligament. ACL surgery has a high success rate.

Athletes and active adults involved in sports who want to return to their previous level of activity generally receive the most benefit from ACL surgery.

Types of ACL Surgery

ACL surgery can be performed with several different graft choices. These include patellar tendon and hamstring tendon (autografts) and donor tissue (allograft). Each of the choices has advantages and disadvantages.

1. Patellar Tendon Bone Autograft

In this case, the surgeon uses the patient’s own patella tendon to create a new ACL, which is comprised of a strip of tendon with two tiny bones at each end. One end is from the patella and one end is from the tibia. During the procedure, it is secured with screws inside tunnels that are drilled in the anatomic location of the original ACL’s attachment.

2. Hamstring Autograft

Doctors sometimes will create a new ACL with tissue taken from the patient’s hamstrings. Because this replacement is comprised of soft tissue and no bone, rehabilitation typically isn’t as rigorous at the onset. The hamstring is a group of tendons comprised of three posterior thigh muscles.

3. Donated Tissue (Allograft)

If harvesting tissue from the patient isn’t the ideal option, physicians can use donated tissue to reconstruct the ACL.

Typically, the patient's age and lifestyle help decide the type of graft to be used for ACL surgery.

Each of these operations has pros and cons. The bone-patellar tendon-bone autograft is strong but can be more painful during the post-operative period. The hamstring autograft generally involves easier rehabilitation but it takes longer to return to athletic competition. Using donated tissue speeds the return to everyday activities but takes the longest when it comes to returning to sporting activities.

All these procedures are performed with the aid of a tiny fiber optic television camera and slender instruments that can be inserted through three small incisions. These arthroscopic procedures reduce scarring and the risk of infection when compared to open procedures.

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Our Approach

There are two things in particular that doctors affiliated with the IRONMAN Sports Medicine Institute are doing in an effort to extend the life of reconstructed ACLs.

First of all, it is important that surgeons place the replacement ACL in the exact footprint of the original. This is something that requires an experienced surgeon and is critical to the healing process. It is the only technique that allows the knee to function with its normal internal motion after the completion of the procedure. If the ACL is not reconstructed in the anatomic fashion, then the knee will not move and behave as it did before the injury.

Secondly, it is important that rehabilitation be designed with the intent of enhancing the function of the reconstructed ACL and not just to get the patient up on his or her feet as soon as possible. Once the procedure has been completed, the most important step in achieving an outstanding result is specific and guided physical therapy over the following six to nine months.

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ACL Surgery Recovery


Patients usually begin a scheduled program of physical therapy and targeted exercise one to two weeks after ACL surgery. Some physicians affiliated with the IRONMAN Sports Medicine Institute may begin rehabilitation as soon as the day after surgery. Rehabilitation after ACL surgery typically takes six to nine months but may take up to a year. 

Physical Therapy

Affiliated physicians and Memorial Hermann IRONMAN Sports Medicine Institute physical therapists meet with patients following surgery to outline the goals of physical therapy, which include restoring function and motion as soon as possible and making sure patients are adequately prepared for the next step. Our physicians and therapists are in constant communication with each other to provide a unique team approach ensuring the highest standard of sports medicine rehabilitation. 

Therapists also prepare patients for the mental aspects of ACL recovery, which is particularly important for athletes that will need confidence in their reconstructed knee when returning back to sporting activities.

Physical therapy is an important part of recovery after ACL surgery. Focused exercises restore motion, strengthen the quadriceps and hamstring muscles, and improve joint position awareness that were weakened by the injury. Physical therapy allows active adults and athletes to return to their normal activities and sports safely and helps prevent re-injury.

Restoring range of motion is the aim of the first stage of therapy. After six weeks, patients usually can walk without help and perform simple tasks.

In the next stage of physical therapy, patients begin exercises to regain flexibility and strength, and balance control.

At 12 weeks after surgery, patients usually start a more intense program of exercises with increasing resistance and advanced strengthening techniques that include core strengthening.

After 16 weeks, patients may begin activities such as running, depending on associated injuries.

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Schedule an Appointment

To find out if you're a candidate for ACL surgery or rehabilitation, schedule an appointment with an orthopedic doctor specializing in knee injuries.