Overview of ACL Tears

One of the most common knee injuries, particularly among athletes engaged in high-demand sports is an anterior cruciate ligament (ACL) sprain, or tear.

The ACL is a vital ligament that provides stability to the knee joint. When it tears, it can cause pain, instability, and limitations in knee function. If you have injured your ACL, you may require surgery to regain full function of your knee. This will depend on several factors, such as your injury’s severity and activity level.

Understanding the causes, symptoms, diagnosis, and treatment options for a torn ACL is essential for effective management and recovery.

Knee Anatomy

The Knee is made up of three bones: the femur (thighbone), tibia (shinbone), and patella (kneecap). The kneecap sits in front of the joint to provide protection to the joint.

The bones are connected to other bones by ligaments. There are four primary ligaments in your knee which act like strong ropes holding the bones together and keeping your knee stable.

Collateral Ligaments
These ligaments run along each side of your knee. The medial collateral ligament (MCL) is on the inside of the knee, and the lateral collateral ligament (LCL) is on the outside of the knee. They control the side-to-side motion of your knee and brace it against excessive lateral movement.

Cruciate Ligaments
These ligaments are found inside your knee joint. They cross each other within the joint to form an X, with the anterior cruciate ligament (ACL) in front and the posterior cruciate ligament (PCL) in back. The cruciate ligaments control the front and back motion of your knee.

The anterior cruciate ligament runs diagonally in the middle of the knee and prevents the tibia from sliding forwards, and provides rotational stability to the knee.

The PCL keeps the shinbone from moving too far backwards. It is stronger than the ACL and is injured far less often.

About half of all injuries to the anterior cruciate ligament occur along with damage to other structures in the knee, such as articular cartilage, meniscus, or other ligaments.

Causes of ACL Tears

ACL tears often occur due to sudden and forceful movements, especially deceleration with rotation or impacts on the knee. Common causes include:

• Sports Injuries: High-impact sports that involve rapid changes in direction, jumping, landing, or pivoting, such as football, basketball, hockey, and skiing.
• Direct Trauma: A direct blow to the knee, such as a fall or collision, can lead to a torn ACL.
• Non-contact Injury: Abruptly stopping, changing direction, or landing awkwardly without any external force can cause the ACL to tear.

Symptoms of ACL Tears

The symptoms of a torn ACL can be immediate and often include:

• Pain: Sudden and severe pain in the knee at the time of injury.
• Swelling: Rapid swelling within a few hours after the injury due to bleeding within the knee joint.
• Tenderness: Discomfort on palpation along the joint line
• Instability: A feeling of the knee “giving way” or being unstable, especially during weight-bearing activities.
• Loss of Range of Motion: Difficulty fully bending or straightening the knee.
• Audible Pop: Some individuals report hearing or feeling a “popping” sensation at the time of injury.

Diagnosis of ACL Tears

To diagnose a torn ACL, your orthopaedic knee specialist will perform a comprehensive evaluation, including:

Physical Examination
Assessing the knee’s stability, range of motion, areas of tenderness and function.

Lachman Test and Pivot Shift Test
These are specialised clinical tests used to assess the integrity of the ACL ligament.

A physical examination and a positive Lachman test is usually all that is required to diagnose an ACL tear, however, scans can be used to assess the severity of the injury, and determine whether there are any other structures involved.

Imaging Tests
X-rays are sometimes used to rule out fractures but will not show soft tissue injuries.

An MRI creates the best images of soft tissues like the anterior cruciate ligament. MRI is usually not required to diagnose a torn ACL, however, it allows your doctor to look for injuries to other soft tissue structures in the knee (e.g., meniscus, cartilage), which can be very useful when deciding the best treatment option.

ACL tears are graded on a severity scale.

• Grade 1 Sprains: The ligament is only mildly damaged in a Grade 1 sprain. It has been slightly stretched but is still able to help keep the knee joint stable.
• Grade 2 Sprains: A Grade 2 sprain is when the ligament is overstretched to the point where it becomes lax. This is often referred to as a partial tear of the ligament.
• Grade 3 Sprains: This type of sprain is most commonly referred to as a complete tear of the ligament. The ligament has been torn in half or pulled directly off the bone, and the knee joint is unstable.

Partial tears of the anterior cruciate ligament are not as common; most ACL injuries are complete or near complete tears.

Treatment Options for ACL Tears

The treatment for a torn ACL depends on various factors, such as the patient’s age, activity level, and the extent of the injury.
Treatment options include:

Conservative Management for ACL Tears: For less active individuals or those with partial tears, physiotherapy and bracing may be sufficient to stabilise the knee and restore function.
Surgical Intervention for ACL Tears: Active individuals and athletes with complete ACL tears often benefit from surgical reconstruction to restore knee stability.

Surgical Options for ACL Tears

ACL reconstruction surgery is a common approach to repair a torn ACL. During the procedure:

• Graft Selection: The surgeon uses a tissue graft (usually from the patient’s own hamstring, patellar tendon, or a donor) to reconstruct the torn ACL.
• Arthroscopic Technique: Most surgeries are minimally invasive, using arthroscopic instruments and small incisions.
• Rehabilitation: Post-surgery, physiotherapy is crucial to regain strength, range of motion, and stability of the knee.
• Outcomes: ACL reconstruction surgery has high success rates, with many patients returning to their pre-injury activity levels (provided they have followed a robust rehabilitation programme) within several months to a year post surgery.

ACL Questions & Answers

Can a torn ACL heal on its own without surgery?
Complete tears of the ACL typically do not heal on their own and often require surgical intervention for optimal recovery.

How long does it take to recover from ACL reconstruction surgery?
The recovery period varies from person to person, but it typically takes 6 to 9 months to return to full activity levels after ACL reconstruction surgery.

Can I participate in sports after ACL reconstruction?
Yes, many individuals can return to sports and physical activities after ACL reconstruction and completing rehabilitation successfully.

Are there any nonsurgical alternatives to treat a torn ACL?
For individuals with less active lifestyles or specific types of partial ACL tears, nonsurgical treatments like physiotherapy and bracing may be considered.

Can ACL injuries be prevented?
While it may not be entirely preventable, proper conditioning, warm-up exercises, using protective equipment, and avoiding risky movements can reduce the risk of ACL injuries, especially in sports and high-impact activities.