Anterior Cruciate Ligament (ACL) Injuries

What is the ACL?

The anterior cruciate ligament, or the ACL, is the most important stabilizing ligament of the knee. Ligaments connect bones to bones and thus prevent abnormal motion or shifting. The ACL prevents the knee from sliding forward or rotating anterolaterally. Given the direction of origin and attachment of the ACL, a deficit in this ligament typically will cause problems with twisting and turning activities.

Furthermore, the ACL also provides protection for the menisci of the knee. There are two menisci per knee (medial meniscus and lateral meniscus) and their preservation is vital to prevent the development of osteoarthritis.

What is an ACL Injury?

In most people when the ACL is injured the ligament is stretched beyond its normal limits and tears. The tearing can be complete or partial. In a complete tear the ligament is definitively not competent or functional any longer. In a partial tear, depending on the amount of ligament torn, it still may or may not be competent. Often times, people are told their “ACL is sprained” which means there is some small micro-tearing but not any gross incompetence of the ligament.

A formal classification for an ACL injury is listed below:

  • Grade I: a partial ACL tear
  • Grade II: near complete ACL tear
  • Grade III: a complete ACL tear – the ligament is non-functional

Depending on your age, activity level, amount of arthritis and grade of tear, Dr. Patel will help determine the correct treatment option for you.

Bone bruises are signals on an MRI that can help determine whether an ACL injury occurred, whether the ACL is functional or not (useful in cases of partial ACL injuries) and can also help determine if an injury is acute (recent) or chronic (old). These bone bruises may not be stated on MRI reports by radiologists, but Dr. Patel will help point them out to you during your visit.

Lastly, there are instances in young, skeletally immature (growing) patients where the bone gives before the ligament. In very young patients the ACL is stronger than the bone attachment for the ACL and the same injury that would lead to an ACL tear in an adult, will lead to an avulsion fracture in a young growing patient. These are called Tibial Spine avulsion fractures and essentially ACL equivalent injuries. Dr. Patel uses minimally invasive techniques to fix these injuries without the need for a new ACL.

How does an ACL Injury Occur?

Most ACL injuries are “non-contact” injuries, meaning that the mechanism of injury was not caused by a collision. The foot twists, balance is lost, and the knee torques in a direction and position that is not compatible with the ligament’s normal loading potential. This results in a failure of the ACL. You may have felt a pop, click, pain, and or tenderness, followed by swelling and painful range of motion. ACL tears are common in skiing, basketball, soccer, and football. Females have an approximate 40% greater number of ACL injuries in most sports compared to males. Many theories have been proposed, including anatomical, physiological, and motor control explanations.

What Associated Injuries are Common with an ACL Injury?

When the knee continues to have instability episodes, it is not uncommon to have either the medial or lateral meniscus tear. Lateral meniscus tears are more common than medial meniscus during the actual initial injury; whereas medial meniscus tears can occur in knees in which the ACL is NOT reconstructed. When menisci tear there is much higher risk of the development of osteoarthritis. Because of this, Dr. Patel usually recommends ACL surgery and that an ACL reconstruction be performed in young or otherwise active patients and in almost all patients who report instability with twisting or turning activities. Concurrently, Dr. Patel advocates repairing the meniscus tear if possible.

Other possible injuries include injuries to the articular cartilage, which is the cartilage at the ends of the bone. These are relatively rare and usually do not need treatment.

In contact injuries or injuries of high-energy (motor vehicle accidents, falls from a height, etc), other ligaments can be injured in conjunction with the ACL. The MCL, LCL and the PCL, with their associated structures, provide stability in different directions compared to the ACL. Combined injuries lead to very unstable knees, which may require additional surgical intervention.

What Symptoms does an ACL Injury Cause?

Since ligaments connect bones to bones, they provide stability. An injury to the ACL will cause instability, particularly in rotational, cutting or pivoting movements. People may feel their leg is giving out, shifting or buckling.

In addition to its stability role in the knee, the ACL also provides protection for the menisci of the knee. When the knee continues to have instability episodes, it is not uncommon to have either the medial or lateral meniscus tear. Thus, people can experience pain or mechanical symptoms such as catching or locking if there is a meniscus tear.

How is an ACL Reconstruction Performed?

A well-performed ACL reconstruction surgery requires precise knowledge of the anatomy of the knee, attachment sites of the ACL and knowledge on the other ligaments and structures of the knee. This is called “anatomic” ACL reconstruction. If one fails to replace an anterior cruciate ligament at its correct attachment sites or if other concurrent injuries are not treated, there is a much higher risk of failure of the ACL graft. Reconstructing the ACL at its correct attachment sites typically requires more time and technical skill than “non-anatomic” methods.

While there are two bundles of the ACL, the anteromedial and posterolateral bundles, the current accepted method of reconstruction is as a single ligament rather than two separate ligament grafts. While the double-bundle ACL reconstruction technique appeared very promising initially, a majority of the research performed has shown no clinical benefit of a double-bundled technique.

A large number of ACL reconstruction graft failures are in those patients who have the graft placed too posterior (towards the back) on the tibia with an inability to control rotation of the knee or too anterior on the femur (towards the front) or too central on the femur (effectively only reconstructing the anteromedial bundle), which leads to either stretching of the reconstruction graft or failure to control knee rotational laxity.

If you have endured knee trauma and are interested in learning more about ACL Injury and developing an ACL treatment plan specific to your needs and injuries contact us now.

Failures of ACL reconstructions from incorrect placement of the graft led to extensive research and improvement in surgical technique. Thus, the technique of ACL reconstructions has changed dramatically over the last decade in orthopaedic surgery. ACL reconstruction grafts performed prior to 5-10 years ago were usually placed more centrally on both the tibia and femur and many of these patients have continued problems with rotation instability. The focus now is on anatomic reconstruction – Dr. Patel is specially trained in this form of surgery. The reconstruction tunnel is drilled at the anatomic attachment site of the ACL on the tibia and a closed socket tunnel is drilled at the ACL attachment site on the femur. The graft is pulled into the joint and fixed in place with screws or buttons. Dr. Patel performs this via a minimally invasive arthroscopic approach, allowing for less pain post-operatively for the patient.

Arthroscopic ACL reconstruction with Dr. Patel can be performed within an hour and is an outpatient or same day surgery.

ACL surgery is typically performed after swelling has subsided and the patient has near full range of motion, particularly full extension. Exceptions to this timing include combined ACL and other ligament injury as well as a need for more urgent intervention when there is a displaced meniscus (bucket-handle) tear. This is usually 2-6 weeks after injury.

Which Graft should be Used for ACL Reconstruction Surgery?

There are commonly three graft choices when it comes to ACL reconstruction surgery: patellar tendon autograft (patient’s own tissue), hamstring autograft (patient’s own tissue) or allograft (cadaveric tissue). For patients under the age of 40, autograft is recommended as it has been shown in multiple well-conducted studies to have lower failure rates compared to allograft/cadaveric tissue. Allograft is suitable for patients over the age of 40-45 years and less active. Dr. Patel will not perform allograft ACL reconstruction in younger patients given the 18% failure rate documented in multiple studies.

Between patellar tendon autograft and hamstring autograft the clinical results at one-year and long-term are equivalent – in other words, both are reliable options. Dr. Patel performs both patellar tendon and hamstring reconstructions and will help the patient make the choice that is best for them during surgical consultation.

What is the Post-Operative Protocol for ACL Reconstruction?

For an isolated ACL reconstruction without any additional ligament or meniscus repair, Dr. Patel advocates immediate weight-bearing (walking) and no bracing. Since Dr. Patel performs an anatomic ACL reconstruction, the graft does not need to be protected from motion or walking. Physical therapy is started within days of surgery and is essential for a full recovery. In the initial period after surgery the physical therapist will assist with reactivation of the quadriceps mechanism, edema control, patella mobilization, maintenance of full knee extension and regaining knee motion.

Overall, physical therapy will typically last 4 months with advancements in activity each week and month. For example, patients will be doing squats around week 6, and running around week 12. Most patients feel great at the conclusion of physical therapy and Dr. Patel will have them undergo objective testing to evaluate if they are ready to return to sports. In the past, many surgeons tried to get their patients back to full activities by 5 or 6 months. While most patients will feel relatively great at this time point, more recent data has suggested that waiting up to 8-9 months may be more advantageous in that the rate of retear goes down significantly.

What is a Typical ACL Recovery Time?

Most patients feel great at the conclusion of physical therapy and Dr. Patel will have them undergo objective testing to evaluate if they are ready to return to sports.