ACL Tears

The anterior cruciate ligament, also referred to as the ACL, is a ligament located within the knee capsule. It prevents the anterior translation of the tibia (The shin bone) in relation to the femur (The thigh bone), thereby creating stability within the knee that is required for most strenuous physical activity. ACL tears are a common injury throughout sports and other physical activities. ACL tears occur in a variety of mechanisms ranging from non-contact scenarios to other more physical cases.

Causes:

ACL tears can be split into two main categories: non-contact and contact-related scenarios

Non-Contact:

1. Sudden deceleration: In many sports, athletes need to slow down rapidly after running at high speeds. The sudden deceleration places an immense amount of weight on the ACL which provides stability for the knee. In this case, the tibia would translate anteriorly creating the tear.

2. Rapid Changes in Direction: In sports like football and soccer, athletes constantly change directions, which puts a great deal of weight on the ACL to shift and change direction. Similar to situations involving sudden deceleration, rapid changes in direction put the athlete at risk for an ACL tear

3. Hyperextension of the Knee: Often, we see hyperextensions occur in high-impact sports. A hyperextension occurs when the knee bends beyond its normal range. Although very rare, if hyperextension is severe enough, it can directly lead to an ACL tear. The most common injury associated with hypertension is a PCL tear.

4. Q-Angle (Quadriceps Angle) in Female Athletes: Two lines in the leg make up the Q-angle measurement: one from the hip to the kneecap and another from the kneecap to the shin bone. Female athletes tend to have a larger Q-angle because of differences in body shape. A few factors that contribute to a larger Q-angle in female athletes are increased pelvic width and shorter femur length. The Q-angle plays no small role in the context of ACL tears, as a study conducted by the NCAA declared that female athletes are six times more likely to endure an ACL tear than their male counterparts. This is because, in females, the knee is already placed in a position of valgus, making the ACL more vulnerable.

Contact:

• Direct connection/collision: Sudden, forceful impacts on the knee can lead to ACL tears. (forcing knee into valgus etc. explain the mechanism)

• As a result of a collision, the knee may move into a valgus position. In a valgus position, the angle between the thigh bone (femur) and lower leg bone (tibia) is increased beyond its normal range, and puts excess stress/pressure on the ACL which ultimately leads to a tear.

Symptoms: 

Symptoms:

• A popping sound/sensation when the injury occurs

• Limited range of motion following the injury

• Knee instability creating difficulty bearing weight

• Feeling pain and discomfort while walking

Pictured Left is a normal, intact ACL

Diagnosis: 

• Physical Examination: If you think you tore your ACL, you can visit your local doctor who can perform a series of physical tests. Some things they may test are knee stability, range of motion, and signs of swelling or tenderness. Furthermore, some special tests that can be used to aid in a diagnosis are Lachman’s Test and the Anterior Drawer Test. Both tests check for the integrity of the ACL and a positive sign would indicate a torn ACL.

• Imaging Tests: A common response to an ACL tear is to get an MRI. An MRI allows a doctor to view organs, tissues, and the skeletal system. Using the MRI, they can confirm the injury and determine its extent.

Treatment Options:

There are two primary ways to treat an ACL tear. These two methods are surgical and non-surgical.

• Surgical: A full and complete tear of the ACL will require surgery in order to reconstruct the ACL. In the surgery, doctors replace torn ligaments with a graft. A graft is a healthy substitute that can come from the patient’s own tissues or a cadaver.

• Non-Surgical: Incomplete tears of the ACL are much easier to treat. The patient will need time, rest, rehabilitation exercises, and a brace. However, many doctors do not advise non-surgical repair as a proper course of action because it may not give the knee the proper stability it needs in order to function effectively.

Rehabilitation & Recovery Period:

The recovery period consists of four stages: Acute Stage, Pre-surgical Stage, Post-surgical Stage, and Return to sport

• Acute Stage: The acute stage begins right after the time of the injury. Patients should follow the RICE (rest, ice, compression, and elevation) protocol and participate in simple and moderate exercises.

• Pre-surgical Stage: This stage focuses on restoring the patient’s normal knee motion. The most important aspect of this stage is incorporating various methods to evaluate muscle strength and proprioception. 

• Post-surgical Stage: During this stage, the patient will increase the complexity and intensity of various rehabilitation exercises. Some of the primary focuses include managing pain and reducing swelling. Rehabilitation exercises are good for the patient because they help restore flexibility and function without any added complications.

• Return to Sport: This may be the last stage of the torn ACL recovery process, but there are still many precautions that need to be taken before fully engaging in sports. Researchers suggest that the injured leg should perform at least 90% as well as the uninjured leg before returning to sports. An effective way to evaluate the durability of the injured leg is through a variety of hopping tests. If pain is still present during and after these tests, then returning back to sports may not be a safe option.

• Duration: Each patient’s path to recovery is different, but the typical period for a full recovery ranges from 9-12 months. More crucial than the rehab duration is the pace at which the patient rehabs. Gradually and safely rehabbing should be the number one priority of all patients who fall victim to ACL tears.

• Return to Activity: Recovering at a moderate pace is essential if you wish to engage in physical activity again. Returning to play too quickly places the athlete at a higher risk for re-injury. It is important to re-establish knee stability and full function. If the ACL is reinjured, this can lead to an increased risk of osteoarthritis in the knee joint, a degenerative joint disease in which joint tissues break down over time.

Sources: 

“ACL Injury.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 1 Dec. 2022, www.mayoclinic.org/diseases-conditions/acl-injury/symptoms-causes/syc-20350738.

“ACL Tear: Symptoms and Treatments for a Torn ACL: HSS.” Hospital for Special Surgery, www.hss.edu/condition-list_torn-acl.asp. Accessed 24 Nov. 2023.

“Anterior Cruciate Ligament (ACL) Injuries - Orthoinfo - Aaos.” OrthoInfo, orthoinfo.aaos.org/en/diseases--conditions/anterior-cruciate-ligament-acl-injuries/. Accessed 24 Nov. 2023.

“Anterior Cruciate Ligament (ACL) Rehabilitation.” Physiopedia, www.physio-pedia.com/Anterior_Cruciate_Ligament_(ACL)_Rehabilitation. Accessed 24 Nov. 2023.

“Anterior Cruciate Ligament (ACL) Tears (for Teens) - Nemours Kidshealth.” Edited by Alvin Wei-i Su, KidsHealth, The Nemours Foundation, Jan. 2019, kidshealth.org/en/teens/acl-injuries.html.

Cleveland Clinic medical. “ACL Tear & Injury: Symptoms & Recovery.” Cleveland Clinic, my.clevelandclinic.org/health/diseases/16576-acl-tear. Accessed 24 Nov. 2023.