ACL Tear
The ACL (anterior cruciate ligament) is the knee ligament most frequently injured, often due to sports-related activities. If you tear your ACL, surgery is typically required to repair it. Most individuals fully recover and are able to return to sports without long-term issues. Recovery from an ACL tear usually takes six to nine months.
What is an ACL tear?
An ACL tear is an injury to the anterior cruciate ligament (ACL) in your knee.
The ACL is one of the key ligaments that connects your thigh bone (femur) to your shin bone (tibia). Each knee has one ACL, which forms an “X” inside the knee along with the posterior cruciate ligament (PCL)—the ACL is at the front, and the PCL is at the back.
The ACL acts like a strap, stabilizing the knee and preventing it from bending or twisting beyond its natural range. Forces that push the knee past this limit—such as sudden twists, jumps, or impacts—can cause an ACL tear.
ACL tears are common, especially in athletes. You should see a healthcare provider if you experience knee pain, particularly after an injury or vigorous physical activity.
Types of ACL injuries
Healthcare providers usually grade ACL injuries and tears. These grades are a quick way to describe the extent of your injury. ACL injury grades range from one (the least severe) to three (the most severe):
- Grade one: The injury stretched your ACL enough to damage it, but it’s still in one piece and holding your knee bones together.
- Grade two: The injury stretched your ACL so much that it was partially torn and loosened.
- Grade three: A complete tear — your ACL is in two pieces.
What does an ACL tear feel like?
Most people are aware of the exact moment they tear their ACL, as sports injuries or other traumas that cause ACL tears are often very noticeable.
Common signs of an ACL tear include:
A popping sound or sensation in the knee at the time of injury
The knee giving out, feeling unstable or weak
Pain in the knee, which can range from severe to mild discomfort
If you injure your knee—especially if you hear or feel a pop—it’s important to see a healthcare provider for evaluation.
How common are ACL injuries?
ACL injuries are quite common, with the anterior cruciate ligament being the most frequently injured ligament in the knee. Experts estimate that 100,000 to 200,000 people in the U.S. experience an ACL tear each year.
Symptoms and Causes
What are ACL tear symptoms?
The most common ACL tear symptoms include:
- Feeling or hearing a pop in your knee.
- Swelling.
- Pain (especially when you try to put weight on your knee).
- Weakness or feeling like your knee has given out.
- Losing your range of motion (how far you can move your knee).
What causes ACL tears?
Anything that places excessive force on the knee can cause an ACL tear, which occurs when the knee bends or twists beyond its normal range of motion.
The most common causes of ACL tears are:
Sports injuries
Car accidents
Falls
ACL tear risk factors
Anyone can suffer an ACL tear, but they are particularly common among athletes—especially in sports that involve sudden stops, twists, or changes in direction. Sports frequently associated with ACL injuries include:
Soccer
Football
Basketball
Gymnastics
Lacrosse
What are the complications of an ACL tear?
The forces that cause an ACL tear can also damage other parts of your knee.
During an ACL injury, you might also injure or tear other ligaments, such as:
Medial collateral ligament (MCL)
Lateral collateral ligament (LCL)
Posterior cruciate ligament (PCL)
Other injuries that can occur alongside an ACL tear include:
Bone fractures
Meniscus tears
Muscle strains
Diagnosis and Tests
How are ACL tears diagnosed?
A healthcare provider diagnoses an ACL tear through a combination of a physical exam and diagnostic tests. They will ask about your symptoms, examine your knee, and want to know what you were doing when the injury occurred and when you first noticed symptoms.
During the exam, your provider may move your knee and leg in various ways to assess stability and function. Some movements might be uncomfortable, so it’s important to let them know if any motion causes pain or worsens your symptoms.
You will likely need one or more imaging tests to confirm the diagnosis, such as:
X-rays
Computed tomography (CT) scan
Magnetic resonance imaging (MRI)
Management and Treatment
How are ACL tears treated?
Treatment for an ACL tear depends on the severity of the injury and any additional knee damage.
Immediate care: Avoid sports or activities that put stress on your knee, and follow the RICE method:
Rest: Stop the activity that caused the injury and avoid overusing your knee while it heals.
Ice: Apply a cold compress or ice pack (wrapped in a thin towel) for 15 minutes at a time, several times a day.
Compression: Use an elastic bandage to help reduce swelling.
Elevation: Keep your knee and leg raised above heart level whenever possible.
Additional treatments may include:
Crutches to limit weight-bearing
Knee brace for stability
Over-the-counter pain medication such as NSAIDs or acetaminophen
Physical therapy to restore strength, flexibility, and function
Can an ACL tear heal on its own?
A torn ACL cannot heal on its own, though some people—especially with a low-grade tear—can manage daily activities without surgery. However, athletes or individuals who want to return to physical activity typically need surgery to repair the ACL. Most people with an ACL tear opt for surgical repair to restore knee stability and function.
ACL tear surgery
Surgery to repair ACL or other knee injuries is typically done as an outpatient procedure, allowing you to go home the same day. Your surgeon will usually perform a knee arthroscopy, a minimally invasive technique that uses small incisions and a camera to repair the tear inside your knee. Be sure to ask your surgeon about what to expect before, during, and after the procedure.
Outlook / Prognosis
How long does it take to recover from a torn ACL?
Recovery from a torn ACL generally takes six to nine months, though competitive athletes may require a bit more time before fully returning to their sport.
Your healthcare provider will guide you on when it’s safe to resume physical activity. Avoid returning to sports or exercise before your ACL has healed, as doing so increases the risk of re-injury.
Prevention
How can I prevent a torn ACL?
There’s no guaranteed way to prevent an ACL tear, especially for athletes, as most tears result from unexpected sports injuries or accidents. However, you can take steps to reduce your risk:
During sports or physical activity:
Wear appropriate protective gear.
Don’t “play through the pain” if your knee hurts.
Allow time for rest and recovery after intense activity.
Stretch and warm up before exercising or playing sports.
Cool down and stretch afterward.
Participate in offseason knee and lower-body strengthening programs to prepare your joints for the demands of your sport.
General safety tips to reduce injury risk:
Avoid planting your foot and pivoting over your knee, a common cause of ACL and meniscus injuries.
Keep your home and workspace free from clutter to prevent trips and falls.
Use proper tools or equipment to reach high places—never stand on chairs, tables, or countertops.
Use a cane or walker if you have difficulty walking or are at higher risk of falls.
Living With
Can you walk if your ACL is torn?
Some people can walk with a torn ACL. But don’t force yourself to move or use your knee if it hurts. Visit a healthcare provider if you feel pain or have other knee injury symptoms. Putting more stress on your injured ACL can make a small tear worse.
When should I see my healthcare provider?
See a healthcare provider promptly after injuring your knee, especially if you notice new symptoms or if the pain worsens.
Seek immediate care in the emergency room if your injury involves significant trauma, such as a car accident or a serious fall, as these events can cause additional injuries that may not be immediately apparent.
What questions should I ask my doctor?
Here are important questions to ask your healthcare provider after a knee injury:
Do I have a torn ACL or another type of knee injury?
What grade is the tear? (Partial or complete)
Should I have surgery, or are other treatments appropriate?
How long will it take before I can safely return to workouts or sports?
What is the risk of re-injuring the same ACL in the future?
Additional Common Questions
Will an ACL tear happen again?
There is a small risk of re-tearing the same ACL, even after surgical repair. Fewer than 10% of people experience a repeat ACL tear. Discuss your individual risk and expectations with your healthcare provider or surgeon.
Is an ACL tear “career-ending” for an athlete?
Most ACL tears are not career-ending, but it’s important not to rush your recovery. With proper rehabilitation, most people can return to sports without long-term problems. Gradual rehab after surgery helps restore your knee’s strength, stability, and flexibility, preparing you to safely resume athletic activities.
Always check with your provider or surgeon before returning to sports to know when it’s safe to resume practice or training.
