ACL Knee Injury Overview

An ACL knee injury is common with participation in high impact sports. This typically occurs from sudden forceful changes in the position of the knee. It can lead to pain, swelling, and poor function of the knee. Without quick attention and treatment, it can have lasting effects on knee function and quality of life. Keep reading to learn about causes, symptoms, and what to expect with recovery.

What is an ACL Tear?

An ACL tear is a sprain of the anterior cruciate ligament in the knee. The ACL ligament is the most common one to be torn of the four ligaments found in the knee. It has a high injury incidence rate with high impact sports. The most common age groups to sustain this injury ranges from 15 to 45 years of age. This is due to the more active lifestyle typically sustained in this age range. The ACL is paramount in providing stability to the knee, particularly with forward movement. It can be partially torn or completely severed, resulting in differing losses of knee function.

Causes of an ACL Tear

ACL injuries occur most commonly during sports. The most high-risk sports include football, downhill skiing, soccer, and basketball. Causes of an ACL tear include:

• Direct impact on the knee
• Twisting the knee with the foot planted
• Extreme hyperextension of the knee
• Sudden stops, especially from a higher speed
• Awkward placement of the lower leg when landing from a jump
• Any awkward movement of the knee when the foot is firmly planted on the ground 
• Misstepping on stairs, ladders, thresholds, ice, etc.

ACL Tear Symptoms

Knowing and recognizing symptoms of an ACL tear can help you get prompt treatment and prevent further injury to the knee. With an ACL tear, injury to other tissues in the knee is common too. Thus, it is important to have a professional to do a full assessment of the knee damage done. That way, proper steps can be taken in the recovery process.

Most people feel some sort of “pop” or “giving way” sensation in their knee during the movement that caused the injury. This usually leads to an immediate feeling of instability. Other symptoms that you might experience include:

• Swelling, typically a quick onset
• Knee pain, initial sharp pain followed by deep aching
• Severe hamstring stiffness, tension, or even cramping (a protective mechanism)
• Weakness of the thigh (mild to severe)
• Inability to bear weight through the leg
• A feeling of instability with use of the leg, particularly with steps, jumping and pivoting
• Limited knee range of motion (flexion and extension)
• Tenderness to touch around the knee joint

Types of ACL Tears

ACL tears are typically identified as one of three different grades depending on the severity of the damage. These grades are:

Grade 1 Tear

Described as a mild injury or stretch to the ligament. Minimal time for recovery is needed and stability of the knee remains intact. 

Grade 2 Tear

The least common grade sustained. It is described as a partially stretched or torn ligament. Stability may or may not be intact with daily activities and sports.

Grade 3 Tear

A severe or complete tear of the ACL ligament resulting in extreme instability of the knee.

ACL Recovery and Outlook

ACL Recovery typically takes 6 to 9 months, depending on the tear and what treatment options are determined to be the best for you. This will depend on your age, grade of ligament tear, and involvement in sports. When possible, a conservative approach will always be taken first focusing on restoring knee function via swelling management, range of motion, and strengthening with a physical therapist. With proper treatment and a good response from the knee, you can expect to make a full recovery.

If the tear is severe or there is excessive instability or laxity in the knee joint, surgery is another option. During a surgical procedure, the ACL will be tightened or re-attached to restore stability and function. In the end, full recovery from an ACL tear takes time and a very gradual return to daily activities as it heals.

For more details about the treatment process, see ACL Tear Rehab.

ACL Tear Prevention

What sports you play, fitness level, gender, previous injuries, and age all determine your risk for an ACL tear and other knee injuries. A focus on knee injury prevention is now common with higher impact sports, particularly for women. Programs typically focus on knee proprioception, strength training of the legs and core, and full-body coordination with high-level activities. The most popular programs for athletes are about six weeks long and help prepare athletes for their seasons.

Full body agility, fitness, and coordination will minimize the risk of ACL tears. Even if you aren’t an athlete, having a well-balanced fitness routine will help keep the knee strong and healthy. When in doubt, it’s best to talk to a healthcare professional as soon as possible to get your knee health back on track.

Sources:

https://www.mayoclinic.org/diseases-conditions/acl-injury/symptoms-causes/syc-20350738

https://www.hopkinsmedicine.org/health/conditions-and-diseases/acl-injury-or-tear