A ligament is a band of tissue that connects bone to bone. The anterior cruciate ligament (ACL) is located inside your knee joint and connects the bones of your upper and lower leg.
An ACL injury occurs when the ligament is stretched or torn. A partial ACL tear occurs when only part of the ligament is torn. A complete ACL tear occurs when the entire ligament is torn into two pieces.
More About Your Injury
The ACL is one of several ligaments that help keep your knee stable. It helps keep your leg bones in place and allows your knee to move back and forth.
An ACL injury can occur if you:
- Get hit very hard on the side of your knee, such as during a football tackle
- Twist your knee
- Quickly stop moving and change direction while running, landing from a jump, or turning
Skiers and people who play basketball, football, or soccer are more likely to have this type of injury. Women are more likely to tear their ACL than men when they participate in sports.
What to Expect
It is common to hear a "popping" sound when an ACL injury occurs. You also may have:
- Knee swelling within a few hours of injury
- Knee pain, especially when you try to put weight on the injured leg
If you have a mild injury, you may notice that your knee feels unstable or seems to "give way" when using it. ACL injuries often occur along with other knee injuries, such as to the meniscus and cartilage. These injuries may need to be treated with surgery.
After examining your knee, your doctor may order
- An MRI of the knee. An MRI is a device that can take pictures of the tissues inside your knee. The pictures will show whether these tissues have been stretched or torn.
- An x-ray to see if there is any damage to the bones in your knee.
If you have an ACL injury, you may need:
- Crutches to walk until the swelling and pain get better
- A brace to support and stabilize your knee
- Physical therapy to help improve joint motion and leg strength
- Surgery to reconstruct the ACL
Some people can live and function normally with a torn ACL. However, most people feel like their knee is unstable and may "give out" with activity. Unrepaired ACL tears can lead to further knee damage.
Self-care at Home
Follow R.I.C.E. to help reduce pain and swelling:
- Rest your leg. Avoid putting weight on it.
- Ice your knee for 20 minutes at a time 3 to 4 times a day.
- Compress the area by wrapping it with an elastic bandage or compression wrap.
- Elevate your leg by raising it above the level of your heart.
You can use ibuprofen (Advil, Motrin), or naproxen (Aleve, Naprosyn) to reduce pain and swelling. Acetaminophen (Tylenol) helps with pain, but not with swelling. You can buy these pain medicines at the store.
Talk with your doctor before using pain medicines if you have heart disease, high blood pressure, kidney disease, or have had stomach ulcers or internal bleeding in the past. DO NOT take more than the amount recommended on the bottle or by your doctor.
After your injury, you should not play sports or other activities until you and your doctor decide what treatment is best for you.
If you have surgery to repair your ACL:
- You will need physical therapy to regain the full use of your knee.
- Recovery after surgery can take about 6 months. But you should be able to do the same activities you did before.
If you do not have surgery:
- You will need to work with a physical therapist to lessen swelling and pain and regain enough strength in your leg to resume activity. This may take a few months.
- Depending on your injury, you may not be able to do certain types of activities that could re-injure your knee.
When to Call the Doctor
Call your health care provider if you have an increase in swelling or pain or self-care does not seem to help.
Cruciate ligament injury - aftercare; ACL injury - aftercare
Amy E, Micheo W. Anterior cruciate ligament tear. In: Frontera WR, Silver JK, Rizzo TD Jr, eds. Essentials of Physical Medicine and Rehabilitation. 2nd ed. St. Louis, MO: Elsevier Saunders; 2008:chap 55.
Honkamp NJ, Shen W, Okeke N, Ferretti M, Fu F. Knee. In: DeLee JC, Drez D Jr, Miller M, eds. DeLee & Drez's Orthopaedic Sports Medicine. 3rd ed. St. Louis, MO: Elsevier Saunders; 2009:chap 23.
Miller III RH, Azar, FM. Knee injuires. In: Canale ST, Beaty JH, Daugherty K, Jones L, et al. Canale & Beaty: Campbell's Operative Orthopaedics. 12th ed. Philadelphia, PA: Elsevier Mosby; 2013:chap 45.
Review Date 5/9/2015
Updated by: C. Benjamin Ma, MD, assistant professor, chief, sports medicine and shoulder service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.