Anterior Cruciate Ligament Tears

Anatomy of the Knee


The knee joint is basically a hinge in which three bones meet: the femur, the tibia, and the patella (knee cap).  These bones are held together by four major ligaments.  The medial collateral ligament (MCL) and the lateral collateral ligament (LCL) are found on the sides of your knee and control its sideways motion.

The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) form a cross inside your knee joint.  Together the cruciate ligaments control the knee’s back and forth movement and provide rotational stability.  The ACL also prevents the tibia from sliding out in front of the femur.

Types of ACL Injuries

ACL tears can be described as partial or complete.  A partial tear occurs when the ligament has been stretched and may not be able to keep the knee joint stable.  The majority of ACL injuries are complete tears that often lead to knee instability.

About half of all injuries to the ACL occur in combination with damage to other parts of the knee, such as a collateral ligament, meniscus or cartilage.

Causes of ACL Injury

There are several ways to injure the ACL:

  • Rapid pivot to change direction
  • Accelerating or decelerating suddenly
  • Awkward landing from a jump
  • Direct contact through collision

Athletes who participate in certain sports are at higher risk for ACL injuries.  Such high demand sports include basketball, soccer, football, and skiing.  Some studies have shown that female athletes in certain sports have significantly higher risk for ACL injuries than males.

Symptoms of ACL Injury

Often a pop is felt or heard and the knee buckles when the ACL is torn.  Other symptoms include:

  • Pain with swelling within hours
  • Loss of full range of motion
  • Tenderness along the joint line
  • Discomfort when walking
  • Continued instability, buckling, or giving way

Immediate Treatment of ACL Injury

If you suspect you have an ACL injury, begin icing the knee immediately and continue icing 15 minutes on with 10 minutes off for the first few days.  You can take an over-the-counter anti-inflammatory medicine using the dosages indicated on the label.  Apply light compression with an ACE wrap and avoid bearing weight on the knee.  Typically immobilization or bracing is not desirable as this can lead to stiffness and atrophy.

Diagnosis of an ACL Injury

It is best to have the knee examined and x-rays taken within the first few days following any severe knee injury.  X-rays will not confirm an ACL tear but can show if any bones have been fractured.  During a physical examination, the doctor will check the structures of your injured knee, comparing them to your non-injured knee.  If the ACL is torn, the physician will usually feel increased forward motion of the tibia in relation to the femur.  Although a physical examination alone is usually enough to diagnose an ACL tear, an MRI may be ordered to confirm the presence of the tear as well as to check for damage to other knee structures such as the meniscus.

Treatment Options

Nonsurgical ACL Treatment 

A partially torn ACL generally has a favorable prognosis, with a recovery period of three to six months.  Most physicians will recommend a complete course of physical therapy and close clinical observation for partial ACL tears, keeping an eye out to identify those patients who continue to exhibit instability.  These patients may later opt for surgery.

Even with a complete ACL tear, nonsurgical treatment can be reasonable for some patients.  Nonsurgical treatment may be indicated in patients:

  • Who do not have any other concurrent injuries
  • Who show no symptoms of knee instability in everyday activities
  • Are willing to give up high-demand sports
  • Who do not do manual work
  • Live sedentary lifestyles

If the doctor and patient decide to opt for non-surgical treatment, physical therapy will begin after swelling subsides. The goal of this therapy will be to restore function to the knee and strengthen the leg muscles that support it.

Surgical ACL Treatment – ACL Reconstruction

If an ACL injury results in instability that significantly affects quality of life, or if non-surgical treatment fails to improve your quality of life, ACL reconstruction may be necessary.  Even if surgery is indicated from the beginning, reconstruction usually is delayed until inflammation can resolve and some range of motion has returned.  Performing ACL reconstruction too early increases the risk of scar forming in the knee joint, which can cause loss of knee motion.

ACL reconstruction is done arthroscopically through small incisions. During an ACL reconstruction surgery, a substitute graft made of tendon replaces the ligament.  Common sources for these grafts include:

  • Patellar tendon autograft, where the tissue is taken from the patient’s patellar tendon along with a bone plug from the shin and kneecap
  • Hamstring tendon autograft, where tissue is taken from the patient’s hamstring tendons
  • Quadriceps tendon autograft, where tissue is taken from the patient’s quadriceps tendon and a bone plug from the upper end of the knee cap is used
  • Cadaver allograft, which can be taken from any of several tendons

Your surgeon will discuss with you which type of graft is best for treating your particular injury.

Surgical Complications of ACL reconstruction

Risks and complications associated with ACL reconstruction can include:

  • Infection
  • Bleeding from a puncture of the popliteal artery
  • Numbness of the leg near the incision
  • Blood clots
  • Recurrent instability due to rupture or stretching of the reconstructed ligament
  • Stiffness
  • Rupture of the patellar tendon or patella fracturing can occur due to weakening at the site of graft harvest in patellar tendon autografts
  • Knee cap pain
  • Growth plate injury in children

Post-Surgical Rehabilitation

The patient’s dedication to rigorous physical therapy is vital to the success of ACL reconstructive surgery.  Early emphasis in rehabilitation is on regaining the ability to fully straighten the knee and restoring quadriceps control.  The knee should be iced regularly to decrease pain and swelling.  Your physician will let you know when you can return to weight-bearing status.  Physical therapy will continue until full knee range of motion, muscle strength, and functional use of the knee has been fully restored.

  • Do all ACL tears need surgery?

    Not necessarily.  Some people who don’t participate in sports or high demand activities at work may be able to adjust their lifestyle to cope with a torn ACL.  Age, activity level, and the amount of arthritis in the knee are all important factors in considering ACL reconstruction.

  • Can my ACL just be stitched back together?

    No, the ACL generally tears in such a way that the ends of the ligament are shredded, resembling the end of a mop.  Even if the ACL can be repaired, or stitched back together, studies have shown terrible results with this technique and it almost always leads to re-tear or instability of the knee.  Reconstruction, making a new ACL from a graft, is the best way to treat an ACL tear.

  • Can I still play sports after ACL surgery?

    Yes, the goal of ACL reconstruction is to return you to your previous level of function.  It generally takes anywhere from 6-12 months to return to sports after an ACL reconstruction, even in elite-level athletes.  

  • Am I too old for ACL reconstruction?

    Activity level is a more important consideration than age when determining whether surgery should be considered. Active adults involved in high-demand sports and heavily manual work are generally candidates for ACL reconstruction.

  • Is my child too young for ACL reconstruction?

    In the past, pediatric ACL surgery wasn’t recommended due to the risk of injury to growth plates. However, with new procedures minimizing this risk, most pediatric ACL tears are recommended for surgical treatment. Most children will not and should not decrease their physical activity levels, so they are therefore at risk of developing secondary injuries if their ACL is not reconstructed. Some of these injuries, such as meniscus tears, significantly increase the risk of early arthritis.

  • Will I have to stay in the hospital after ACL surgery?

    Surgery is performed as an outpatient. Patients go home 2-4 hours after surgery when they can eat and walk with crutches. If you have your own crutches or have already been given a hinged knee brace, please bring them to the hospital with you.

  • How long does ACL surgery take to perform?

    The surgery usually requires approximately 1 hour to perform. Repairing or removing a torn meniscus can add 15-30 minutes to the operation.

  • When can I drive a car after ACL surgery?

    Basically, you can drive when you feel safe and confident behind the wheel so you can avoid getting into an accident. Most patients are able to drive if surgery does not involve their right leg as soon as they stop taking narcotic pain medications and are able to walk without crutches. Decisions on driving after surgery on the right knee should be discussed with your surgeon at your first visit. Driving while under the influence of narcotic medications is extremely dangerous and discouraged in all patients.

  • When can I return to work or school after ACL surgery?

    Motivated people who have a sitting or desk job can usually be back to work by 7-10 days after surgery. Physically demanding jobs may take up to 3-4 months.

  • What is the success rate of ACL surgery?

    90% of patients will have stability nearly equal to the normal knee and will be able to return to full unrestricted activities without any brace.

  • Can I re-injure the graft after ACL surgery?

    Of course, remember that you tore your own natural ligament, so it is theoretically possible to rupture your graft. Fortunately, rupture of the graft is uncommon. You are as likely to tear the ACL in the other knee as to re-tear your reconstructed ligament.

  • Will I need a brace after ACL surgery?

    You will have a hinged knee brace for 4-6 weeks after surgery. Bracing after the intial post-operative period is a matter of preference for most orthopaedic surgeons. While a performance brace can offer some physical support to the knee, it often can provide mental support as well. This rehab protocol can definitely be used without a brace. However for most athletes, especially those in contact sports, I will recommend a brace for the first season back to sports. This brace will be ordered 3-4 months after surgery once strength and muscle size is near normal.

If you have more questions, please call my office at 502-394-6341.