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Experienced athletes know that injury to the knee's anterior cruciate ligament (ACL) can mean spending the season on the sidelines. While ACL injury is uncommon in the general population, athletes — especially young women who play basketball, soccer or volleyball — are susceptible. Treatment of an ACL injury can get you back to your sport, but the best defense is a strong offense. If you're active in a sport that involves pivoting or jumping, learn how your training program can help you avoid an ACL injury.
Ligaments are strong bands of tissue that attach one bone to another. The anterior cruciate (KROO-she-ate) ligament, one of two ligaments that cross in the middle of the knee, connects the thighbone (femur) to the shinbone (tibia) and helps stabilize the knee joint. The ACL may tear, either partially or completely, as a result of a hard twist, sudden stop while running, jump landing or direct blow to the knee. You may experience a loud, painful pop when the ligament is first injured, followed by swelling of the knee.
The pain and swelling of an ACL injury can last for several weeks. While some people can continue to function, most say their knee feels unstable or loose. It may give way if you return to your sport. Short-term treatment can relieve the pain and inflammation, but it takes months for an ACL injury to heal completely. Treatment may include surgery to rebuild the torn ligament, along with an intense rehabilitation program.
At the time of an ACL injury, signs and symptoms may include:
The pain and swelling usually subside after two to four weeks, but your knee may still feel unstable. It may "give way" during twisting or pivoting movements, or feel like it wants to slip backwards.
Most ACL injuries happen during sports and fitness activities. The ligament may tear when you slow down suddenly to change direction or pivot with your foot firmly planted, twisting or overextending your knee. Sports that involve running, turning sharply, pivoting and jumping — especially basketball, soccer and volleyball — put the knee at risk. The ACL can also tear when the tibia is pushed forward below the femur, such as during a fall in downhill skiing. A football tackle or accident also can cause an ACL injury.
ACL injuries are most common among athletes ages 15 to 25. Women are four to six times more likely to tear their ACL, compared with men in the same sports. Women tend to have imbalanced thigh muscles, with stronger muscles at the front of the thigh (quadriceps), compared with those at the back of the thigh (hamstrings). The hamstrings help protect the shinbone from sliding too far forward. When landing from a jump, some women may land in a position that increases stress on the knee.
See your doctor if you experience signs and symptoms of an ACL injury or if your knee feels loose or unable to support your weight. If the injury isn't diagnosed and treated, the cushioning cartilage (menisci) in your knee could be damaged, setting the stage for further joint problems.
If you've injured your knee, don't move the joint. Use a splint to keep your knee straight until a doctor examines it. Avoid returning to play until you've had the injury evaluated.
To diagnose a torn ACL, your doctor first wants to know as much as possible about the injury, such as whether you heard or felt your knee pop, whether your knee swelled up afterward and if you were able to continue being physically active. Your doctor examines your knee in a variety of positions.
Swelling that occurs shortly after the injury usually means there's blood in the joint from torn blood vessels in the damaged ligament. Your doctor may decide to draw the blood out with a needle and syringe. This can reduce pain and make it easier to examine the knee joint.
Often the diagnosis can be made on the basis of the physical exam alone, but you may need X-rays to rule out a bone fracture. If your doctor has questions about the cause or extent of your injury, he or she may order a magnetic resonance imaging (MRI) scan, a painless procedure that uses magnetic fields to create an image of the soft tissues of your body. An MRI can clearly show whether the ACL is partially or completely torn and if other knee ligaments or joint cartilage also is injured.
In the short term, you'll have to stop doing the activities that cause pain until your injured ligament has healed. You may have to take time off work, school and sports.
In many cases, an ACL injury also results in a tear of the meniscus — the cartilage in your knee between the thighbone and shinbone. A cartilage tear increases the risk of future joint problems. An ACL injury also makes your knee more vulnerable to subsequent injuries, especially if you return to the same sport.
A common long-term complication is the early onset of knee osteoarthritis, in which joint cartilage deteriorates and its smooth surface roughens. Up to 90 percent of people with an ACL tear show some signs of osteoarthritis in the involved joint 10 to 15 years later. On average, people who've had an ACL injury develop knee arthritis 15 to 20 years earlier than do those who haven't had a knee injury. This is true even if you have surgery to reconstruct the ligament.
Initial treatment for an ACL injury aims to reduce pain and swelling in the knee, regain normal joint movement and strengthen the muscles around the knee. You and your doctor will then decide if you should have surgery plus rehabilitation or intense rehabilitation alone. Which option is right for you depends on several factors, including the extent of damage to your knee and your willingness to modify your activities. When young children injure their ACL, doctors often recommend postponing surgery until the child's bones have stopped growing.
Short term
To treat the acute injury:
Surgery
A torn ACL can't be sewn back together. The ligament is reconstructed by taking a piece of tendon from another part of your leg and connecting it to the thighbone and shinbone (autograft). If your own tendons don't provide the best replacement for the injured ligament, your doctor may recommend using a tendon from a cadaver (allograft). The cadavers used for allografts have been carefully screened and tested for disease.
You may consider surgery if:
ACL reconstruction surgery is an outpatient procedure using arthroscopic techniques. The surgeon inserts a thin instrument (arthroscope) with a light and a small camera into one or two small incisions. This allows the surgeon to see the inside of the knee joint and make the repairs. After surgery you'll go through a rehabilitation program. In addition to working with a physical therapist, you may wear a special knee brace and will need to avoid activities that put undue stress on your knee. Most people can return to their sports six to nine months after surgery. About nine in 10 people who undergo ACL reconstruction report good to excellent results and satisfactory knee stability.
Nonsurgical rehabilitation
A rehabilitation program without surgery involves physical therapy, modifying your activities and knee bracing. This approach can be effective as long as you're willing to give up the sports and other activities that place extra stress on your knee. You may want to consider rehabilitation alone if:
To reduce your chance of an ACL injury, follow these tips:
If you experience any of the signs and symptoms of ACL injury — a popping sound, severe knee pain, a swollen knee or a feeling that your knee is giving out — see a doctor. In general, the longer you wait to start treatment, the longer it will take to get better. Your doctor or physical therapist may recommend exercises to do at home.
