Anterior Cruciate Ligament (ACL) Injuries

The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee. The incidence of ACL injuries is currently estimated at approximately 200,000 annually, with 100,000 ACL reconstructions performed each year. In general, the incidence of ACL injury is higher in people who participate in high-risk sports, such as basketball, football, skiing, and soccer.

Approximately 50% of ACL injuries occur in combination with damage to the meniscus, articular cartilage, or other ligaments. Additionally, patients may have bruises of the bone beneath the cartilage surface. These may be seen on a magnetic resonance imaging (MRI) scan and may indicate injury to the overlying articular cartilage. 

If you have injured your anterior cruciate ligament, you may require surgery to regain full function of your knee. This will depend on several factors, such as the severity of your injury and your activity level.  Complete ACL ruptures do not have a favorable outcome. After a complete ACL tear, some patients are unable to participate in cutting or pivoting-type sports, while others have instability during even normal activities, such as walking. There are some rare individuals who can participate in sports without any symptoms of instability. This variability is related to the severity of the original knee injury, as well as the physical demands of the patient.

Dr. Wilson is a fellowship trained sports medicine surgeon who specializes in injuries like the ACL.  He trained with some of the world's leaders in ACL surgery and offers the latest and most innovative ACL treatment options and surgical techniques.

Anatomy

Normal Knee

Bones are connected to other bones by ligaments. There are four primary ligaments in your knee. They act like strong ropes to hold the bones together and keep your knee stable.

Collateral Ligaments

These are found on the sides of your knee. The medial collateral ligament is on the inside and the lateral collateral ligament is on the outside. They control the sideways motion of your knee and brace it against unusual movement.

Cruciate Ligaments

These are found inside your knee joint. They cross each other to form an "X" with the anterior cruciate ligament in front and the posterior cruciate ligament in back. The cruciate ligaments control the back and forth motion of your knee.

The anterior cruciate ligament runs diagonally in the middle of the knee. It prevents the tibia from sliding out in front of the femur, as well as provides rotational stability to the knee.

Cause

It is estimated that 70 percent of ACL injuries occur through non-contact mechanisms while 30 percent result from direct contact with another player or object.  The anterior cruciate ligament can be injured in several ways:

  • Changing direction rapidly
  • Stopping suddenly
  • Slowing down while running
  • Landing from a jump incorrectly
  • Direct contact or collision, such as a football tackle

 Several studies have shown that female athletes have a higher incidence of ACL injury than male athletes in certain sports. It has been proposed that this is due to differences in physical conditioning, muscular strength, and neuromuscular control. Other suggested causes include differences in pelvis and lower extremity (leg) alignment, increased looseness in ligaments, and the effects of estrogen on ligament properties.

Symptoms

When you injure your anterior cruciate ligament, you might hear a "popping" noise and you may feel your knee give out from under you. Other typical symptoms include:

  • Pain with swelling. Within 24 hours, your knee will swell. If ignored, the swelling and pain may resolve on its own. However, if you attempt to return to sports, your knee will probably be unstable and you risk causing further damage to the cushioning cartilage (meniscus) of your knee.
  • Loss of full range of motion
  • Tenderness along the joint line
  • Discomfort while walking

Doctor Examination

Physical Examination and Patient History

During your first visit, Dr. Wilson will talk to you about your symptoms and medical history.

During the physical examination, he will check all the structures of your injured knee and compare them to your non-injured knee. Most ligament injuries can be diagnosed with a thorough physical examination of the knee.

Imaging Tests

Other tests which may help Dr. Wilson confirm your diagnosis include:

X-rays. Although they will not show any injury to your anterior cruciate ligament, x-rays can show whether the injury is associated with a broken bone.

Magnetic resonance imaging (MRI) scan. This study creates better images of soft tissues like the anterior cruciate ligament. An MRI machine is located in Dr. Wilson’s office, maximizing your convenience.

ACL tear

MRI of complete ACL tear. The ACL fibers have been disrupted and the ACL appears wavy in appearance

 

Treatment

Treatment for an ACL tear will vary depending upon the patient's individual needs. For example, the young athlete involved in agility sports will most likely require surgery to safely return to sports. The less active, usually older, individual may be able to return to a quieter lifestyle without surgery.

Patients treated with surgical reconstruction of the ACL have long-term success rates of around 90% percent. Recurrent instability and graft failure are seen in approximately 8% of patients.

The goal of the ACL reconstruction surgery is to prevent instability and restore the function of the torn ligament, creating a stable knee. This allows the patient to return to sports.

Nonsurgical Treatment

A torn ACL will not heal without surgery. But nonsurgical treatment may be effective for patients who are elderly or have a very low activity level. If the overall stability of the knee is intact, Dr. Wilson may recommend simple, nonsurgical options.

Bracing. Dr. Wilson may recommend a brace to protect your knee from instability. To further protect your knee, you may be given crutches to keep you from putting weight on your leg.

Physical therapy. As the swelling goes down, a careful rehabilitation program is started. Specific exercises will restore function to your knee and strengthen the leg muscles that support it.

Surgical Treatment

Rebuilding the ligament. Most ACL tears end up needing to be fixed to stabilize the knee. To surgically repair the ACL and restore knee stability, the ligament must be reconstructed. Dr. Wilson will replace your torn ligament with a tissue graft. This graft acts as a scaffolding for a new ligament to grow on.

Grafts can be obtained from several sources. Often they are taken from the patellar tendon, which runs between the kneecap and the shinbone. Hamstring tendons at the back of the thigh are a common source of grafts. Oftentimes, cadaver graft (allograft) can be used.  Dr. Wilson has experience with all different graft types and tailors his treatment and graft choice to the patient and their needs.

Patellar tendon autograft
Patellar tendon autograft prepared for ACL reconstruction.

The middle third of the patellar tendon of the patient, along with a bone plug from the shin and the kneecap is used in the patellar tendon autograft. Occasionally referred to by some surgeons as the "gold standard" for ACL reconstruction, it is often recommended for high-demand athletes and patients whose jobs do not require a significant amount of kneeling.

In studies comparing outcomes of patellar tendon and hamstring autograft ACL reconstruction, the rate of graft failure was lower in the patellar tendon group (1.9 percent versus 4.9 percent). In addition, most studies show equal or better outcomes in terms of postoperative tests for knee laxity (Lachman's, anterior drawer and instrumented tests) when this graft is compared to others. However, patellar tendon autografts have a greater incidence of postoperative patellofemoral pain (pain behind the kneecap) complaints and other problems.

Hamstring tendon autograft

Hamstring tendon autograft

Hamstring tendon autograft prepared for ACL reconstruction.

The semitendinosus hamstring tendon on the inner side of the knee is used in creating the hamstring tendon autograft for ACL reconstruction. Occasionally, an additional tendon, the gracilis, which is attached below the knee in the same area is needed. This creates a two- or four-strand tendon graft. Hamstring graft proponents claim there are fewer problems associated with harvesting of the graft compared to the patellar tendon autograft including:

    • Fewer problems with anterior knee pain or kneecap pain after surgery
    • Less postoperative stiffness problems
    • Smaller incision
    • Faster recovery

Dr. Wilson has published a technique for a minimally invasive hamstring harvest and believes in this as an option.

Allografts. Allografts are grafts taken from cadavers and are becoming increasingly popular. These grafts are also used for patients who have failed ACL reconstruction before and in surgery to repair or reconstruct more than one knee ligament. Advantages of using allograft tissue include elimination of pain caused by obtaining the graft from the patient, decreased surgery time and smaller incisions. 

Prior literature has suggested a higher failure rate with the use of allografts for ACL reconstruction. However, more recent studies have proven that current preparation techniques have made allografts as strong as autografts with equal outcomes.

There are advantages and disadvantages to all graft sources. Dr. Wilson will discuss graft choices with you to help determine which is best for you.

Procedure. Surgery to rebuild an anterior cruciate ligament is done with an arthroscope using small incisions. Arthroscopic surgery is less invasive. The benefits of less invasive techniques include less pain from surgery, less time spent in the hospital, and quicker recovery times.

“All-Inside ACL Reconstruction”.  Dr. Wilson is the only surgeon in the area performing all-inside ACL reconstruction.  This technique has been proven in research to be the most minimally invasive technique available today and has been shown to have the least pain and quickest recovery of any ACL surgical technique.

Timing.  Unless ACL reconstruction is part of the treatment for a combined ligament injury, it is usually not done right away. This delay gives the inflammation a chance to resolve, and allows a return of motion before surgery. Performing an ACL reconstruction too early greatly increases the risk of arthrofibrosis, or scar forming in the joint, which would risk a loss of knee motion.

Rehabilitation

Whether your treatment involves surgery or not, rehabilitation plays a vital role in getting you back to your daily activities. A physical therapy program will help you regain knee strength and motion.

If you have surgery, physical therapy first focuses on returning motion to the joint and surrounding muscles. Dr. Wilson will usually institute this phase of rehab right away on the day after surgery.  This is followed by a strengthening program designed to protect the new ligament. This strengthening gradually increases the stress across the ligament. The final phase of rehabilitation is aimed at a functional return tailored for the athlete's sport.  Because the regrowth takes time, it may be 6-9 months or more before an athlete can return to sports after surgery.

Postoperative Course. In the first 10 to 14 days after surgery, the wound is kept clean and dry, and early emphasis is placed on regaining the ability to fully straighten the knee and restore quadriceps control.

The knee is iced regularly to reduce swelling and pain. Dr. Wilson may dictate the use of a postoperative brace and the use of a machine to move the knee through its range of motion.  You are usually able to start walking on the operated leg right away and can generally be off of crutches within the first week or two.

Rehabilitation. The goals for rehabilitation of ACL reconstruction include reducing knee swelling, maintaining mobility of the kneecap to prevent anterior knee pain problems, regaining full range of motion of the knee, as well as strengthening the quadriceps and hamstring muscles.

The patient may return to sports when there is no longer pain or swelling, when full knee range of motion has been achieved, and when muscle strength, endurance and functional use of the leg have been fully restored.

The patient's sense of balance and control of the leg must also be restored through exercises designed to improve neuromuscular control. This usually takes four to six months. The use of a functional brace when returning to sports is ideally not needed after a successful ACL reconstruction, but some patients may feel a greater sense of security by wearing one and Dr. Wilson often makes one available to his patients.