ACL Tear: Signs, Diagnosis, and When to Get Surgery

An ACL tear is a common knee injury that affects up to 200,000 people in the U.S. every year. Although these injuries are common, it’s normal to have questions about how they occur and when surgery is necessary. Knowing what to expect after an ACL tear and understanding your treatment options can help make your recovery more bearable.

What is an ACL tear?

An ACL tear is a partial or complete rupture of the anterior cruciate ligament (ACL). The ACL is one of the ligaments that help to keep the knee in place. It is a band of tissue that connects the tibia and the femur, the long bones that make up the knee joint. 

The ACL keeps the tibia from sliding over the femur. That’s why, when it ruptures, your joint can become unstable. An ACL tear may also involve damage to other ligaments, bones, cartilage, or a meniscus. 

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ACL tears are grouped based on the severity of the injury. These groupings are:

• Grade 1 (mild injury): Knee remains stable.

• Grade 2 (partial tear): Ligament may be very loose.

• Grade 3 (complete tear): Knee is unstable.

How do you tear your ACL?

ACL injuries can occur due to a direct blow to the tibia, in what’s called contact injuries. But most ACL injuries are noncontact injuries. 

The ligament may tear under the following conditions:

• During sudden movements while the knee is bent and twisted

• While doing cuts and rapid changes in direction

• During pivots and twists

• When landing from jumps, especially if the foot lands flat on the floor

• With inadequate positioning of the hip, knee, ankle, or foot during landing or stopping suddenly 

ACL tears often occur during certain sports that involve these kinds of movement, such as:

• Basketball

• Soccer

• Tennis

• Football

• Volleyball

How is an ACL tear diagnosed?

People with an ACL tear usually hear or feel a pop in their knee, followed by swelling, pain and joint instability. You may feel like your knee “gives way.” These symptoms and a physical exam should be enough to diagnose an ACL tear. 

The physical exam consists of checking for:

• Tenderness, swelling, or bruising in the joint

• Range of motion

• Knee stability

• Clicking sounds in the knee

• Signs of damage to the meniscus

During the exam, your provider will move your knee in different directions while putting pressure on specific areas. Your provider may use imaging tests, as well. X-rays may help rule out fractures, but MRIs can be particularly useful tools. 

An MRI may help to:

• Confirm a diagnosis missed by a physical exam

• Show the severity of the ACL injury

• Check the condition of the other ligaments, tendons, and cartilage

What should you do if you tear your ACL?

If you suspect you have an ACL tear, seek guidance from your healthcare provider. They can help you get the correct diagnosis and get treatment started.

While waiting to connect with your provider, there are some things you can do to help relieve the pain and swelling. At the moment of injury, try:

• Using ice packs

• Resting

• Elevating the leg

• Wrapping the knee with an elastic band

The ACL is slow to heal. Be mentally prepared for an intense rehabilitation period.

What are the treatment options for an ACL tear?

Treatment for an ACL tear varies according to a person’s age, the severity of damage, and their goals. A treatment plan may consist of physical therapy or surgery. 

Nonoperative treatment

Nonoperative treatment for an ACL tear involves rehabilitation. Physical therapy should start soon after the injury to restore range of motion and reduce pain and swelling. This type of rehab involves strengthening the muscles around the knee. This helps with stability and to reduce the risk of further injury.

Many people do well with this conservative treatment approach. People who decide not to have surgery usually do so because they are comfortable not returning to competitive sports. Or they are willing to change to avoid contact sports. 

Surgical treatment

After trying physical therapy, some people may continue to feel that their knee is unstable and decide to have surgery. On top of restoring stability, surgery can help reduce potential damage to the cartilage and meniscus.

Reasons you might consider surgery include:

• You have ongoing knee instability.

• You are a highly active person.

• You have associated injuries that need surgery.

This will be a shared decision-making process with your surgeons and physical therapists. You and your team will consider factors like:

• Your career and what kind of physical activity it demands

• How much family support you have

• Your personal preference

• The costs of the surgery

• The risks of the surgery

What does rehab for an ACL tear involve?

There are two types of rehabilitation programs for an ACL tear: preoperative and postoperative. 

Preoperative rehabilitation (prehab)

After an ACL tear, some people — like elite athletes who need to compete — may go directly to surgery. But, for most people, a period of physical therapy before surgery (prehab) is recommended. Even if you’re not sure about having surgery, it makes sense to have prehab first.

Prehab programs have been associated with better surgical outcomes. The benefits of following one of these programs include:

• Improved strength and mobility in the knee

• Lower rate of reinjury

• Decreased chances of injuring the other knee

Postoperative rehabilitation

The physical therapy that’s done after surgery can be demanding. It typically focuses on:

• Resistance and strengthening exercises

• Neuromuscular exercises (training the nerves and muscles to work together)

• Functional training (working on daily movements)

• Sport-specific training

Some people may return to playing high-level sports after surgery. But surgery does not necessarily guarantee a return to activities or that you won’t have further knee problems. 

How long does it take to recover from an ACL tear?

If you don’t have surgery, rehabilitation may take 4 to 5 months. And rehabilitation after surgery may take about 9 months. But the recovery process can continue for years after formal rehabilitation.

It’s important to know that everybody recovers differently. After an ACL tear, the knee can continue to deteriorate and be prone to osteoarthritis. With surgery, there can be ongoing improvement years after the procedure or the knee may never feel the same. Even with repair, it’s possible to have residual weakness, pain, and limitations for a long time.

There are a few signs of a successful recovery. You are recovering well when:

• Your knee stops giving way.

• Swelling has improved.

• Muscle strength is better.

• You can return to sports or your other activities.

After an ACL repair, you may remain at risk of reinjury. Continued exercise and training are your best tools for prevention. Remember to strengthen the unharmed knee, as well; it may be at increased risk for an ACL tear.

What is the fastest way to recover from an ACL tear?

How fast you recover from an ACL tear may depend on whether you had a slight injury or a complete tear. But, in general, there is not a quick fix for this type of injury. You may need months of personalized, well-planned rehabilitation to recover. 

Can I play sports after an ACL surgery?

Surgery does not guarantee a return to playing the same type or level of sports. Some people may not return to sports at all or may do so at a lower level of competition. 

Your provider may recommend that you consider playing an alternative sport to the one related to your injury to stay active. In general, a gradual return to sports is possible through rehabilitation. But it’s important that you’re physically and mentally ready and that you allow time for healing.

When you first return to playing sports, you may fear a reinjury or may not “trust” your knee. But, with counseling and guidance, you can overcome those fears.  

Why trust our experts?

Written by:

Itza Rivera, MD

Dr. Rivera is a board-certified physical medicine and rehabilitation specialist. She completed her medical degree and residency training at the University of Puerto Rico School of Medicine, and her neuromuscular disorders subspecialty training at Northwestern University.

Edited by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

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