What is an ACL injury?
An ACL injury is the tearing of the anterior cruciate (KROO-she-ate) ligament (ACL) — one of the major ligaments in your knee. ACL injuries most commonly occur during sports that involve sudden stops, jumping or changes in direction — such as basketball, soccer, football, tennis, downhill skiing, volleyball and gymnastics.
Many people hear or feel a “pop” in the knee when an ACL injury occurs. Your knee may swell, feel unstable and become too painful to bear weight.
Depending on the severity of your ACL injury, treatment may include rest and rehabilitation exercises to help you regain strength and stability or surgery to replace the torn ligament followed by rehabilitation. A proper training program may help reduce the risk of an ACL injury.
How common is an ACL injury?
One of the most common knee injuries is an anterior cruciate ligament sprain or tear. Athletes who participate in high demand sports like soccer, football, and basketball are more likely to injure their anterior cruciate ligaments.
Please discuss with your doctor for further information.
What are the symptoms of an ACL injury?
The common symptoms of an ACL injury are:
- Feeling or hearing a “pop” in the knee at the time of injury.
- Sudden instability in the knee. (The knee feels wobbly, buckles, or gives out.) This may happen after a jump or change in direction or after a direct blow to the side of the knee.
- Pain on the outside and back of the knee.
- Knee swelling within the first few hours of the injury. This may be a sign of bleeding inside the joint. Swelling that occurs suddenly is usually a sign of a serious knee injury.
- Limited knee movement because of swelling and/or pain.
After an acute injury, you will almost always have to stop the activity you are doing, but you may be able to walk.
Other health problems can cause symptoms like those of an ACL injury. They include a bone break or injuries to the knee cushions (menisci) or to other ligaments in the knee.
There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.
When should I see my doctor?
If you have any signs or symptoms listed above or have any questions, please consult with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.
What causes an ACL injury?
Ligaments are strong bands of tissue that connect one bone to another. The ACL, one of two ligaments that cross in the middle of the knee, connects your thighbone (femur) to your shinbone (tibia) and helps stabilize your knee joint.
Most ACL injuries happen during sports and fitness activities that can put stress on the knee:
- Suddenly slowing down and changing direction (cutting)
- Pivoting with your foot firmly planted
- Landing from a jump incorrectly
- Stopping suddenly
- Receiving a direct blow to the knee or collision, such as a football tackle
When the ligament is damaged, there is usually a partial or complete tear across the tissue. A mild injury may overextend the ligament but leave it intact.
What increases my risk for an ACL injury?
There are many risk factors for ACL injury, such as:
- Playing sports that involve sudden changes in direction or cutting around other players or obstacles, such as skiing, football, soccer, basketball, baseball, and tennis.
- Making accidental movements that may twist your knee. Examples include falling off a ladder, jumping from an extreme height, stepping into a hole, or missing a step on a staircase.
- Losing muscle tone in legs (from aging or inactivity).
- Having unbalanced leg muscle strength, such as if the muscles in the front of your thigh (quadriceps) are stronger than the muscles at the back of your thigh (hamstrings).
- Previous ACL injuries, especially if your knee sometimes gives out or buckles (chronic ACL deficiency).
Diagnosis & treatment
The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.
How is an ACL injury diagnosed?
During the physical exam, your doctor will check your knee for swelling and tenderness — comparing your injured knee to your uninjured knee. He or she also may move your knee into a variety of positions to assess range of motion and overall function of the joint.
Often the diagnosis can be made on the basis of the physical exam alone, but you may need tests to rule out other causes and to determine the severity of the injury. These tests may include:
- X-rays. X-rays may be needed to rule out a bone fracture. However, X-rays can’t visualize soft tissues, such as ligaments and tendons.
- Magnetic resonance imaging (MRI). An MRI uses radio waves and a strong magnetic field to create images of both hard and soft tissues in your body. An MRI can show the extent of an ACL injury and signs of damage to other tissues in the knee.
- Using sound waves to visualize internal structures, ultrasound may be used to check for injuries in the ligaments, tendons and muscles of the knee.
How is an ACL injury treated?
The goals of treatment for an anterior cruciate ligament (ACL) injury are to:
- Restore normal or almost normal stability in the knee.
- Restore the level of function you had before the knee injury.
- Limit loss of function in the knee.
- Prevent injury or more damage to other knee structures.
- Reduce pain.
You’ll need to work with your doctor to decide whether you should have several months of rehabilitation (rehab) or surgery with rehab. Not all ACL tears need surgery.
Treatment right after an injury
If you know you have injured your ACL, the first treatment consists of:
- First aid to reduce swelling and pain. This may include resting the knee, applying ice, using gentle compression with an elastic bandage, elevating the leg, and taking pain medicines, such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs).
- Using crutches and/or splints in the first few days. If crutches or splints are used for too long, the muscles will become weaker from too little activity. Then movement of the knee will become stiff and restricted.
- Strength and motion exercises to help prepare you for treatment.
What type of other treatment you have depends on:
- How much of your ACL is torn (whether it is a grade I, II, or III sprain).
- When the injury occurred and how stable your knee is.
- Whether other parts of the knee are injured. If they are, it will be harder for the strong parts of your knee to compensate and protect the injured parts.
- Whether you had other knee problems before, such as injuries that caused long-term (chronic) ACL deficiency, or osteoarthritis.
- How active you are.
- Your age and overall health.
- Your willingness and ability to complete a long and rigorous rehab.
Treatment options include:
- Nonsurgical treatment only, such as a physical rehab program.
- ACL surgery to reconstruct the ACL or to reconstruct it and repair other injuries, such as a meniscus tear.
Lifestyle changes & home remedies
What are some lifestyle changes or home remedies that can help me manage an ACL injury?
The following lifestyles and home remedies might help you cope with an ACL injury:
- Exercises that strengthen leg muscles, particularly hamstring exercises, to ensure an overall balance in leg muscle strength
- Exercises to strengthen the core: hips, pelvis and lower abdomen
- Training and exercise for proper techniques and knee position in jumping and landing
- Training to improve techniques for pivoting and cutting
If you have any questions, please consult with your doctor to better understand the best solution for you.
Hello Health Group does not provide medical advice, diagnosis or treatment.
ACL injury. http://www.mayoclinic.org/diseases-conditions/acl-injury/home/ovc-20167375. Accessed August 11, 2017.
Anterior Cruciate Ligament (ACL) Injuries. http://orthoinfo.aaos.org/topic.cfm?topic=a00549. Accessed August 11, 2017.
Anterior Cruciate Ligament (ACL) Injuries - Topic Overview. http://www.webmd.com/a-to-z-guides/tc/anterior-cruciate-ligament-acl-injuries-topic-overview#1. Accessed August 11, 2017.
Review Date: August 11, 2017 | Last Modified: September 13, 2019