A sudden twist or turn, fall or accident can result in a torn or ruptured ACL. An anterior cruciate ligament sprain or tear is one of the most common knee injuries and can happen to anyone, however, girls are up to eight times more likely to have an ACL injury than boys.
Where Is ACL In Your Knee?
The anterior cruciate ligament (ACL) is a ligament, or short band of tough, flexible connective tissue that hold the bones of the knee together. The ACL is located in the center of the knee and controls rotation and forward movement of the shin bone.
The ACL is one of four major ligaments in the knee that give the joint stability and strength. The other three ligaments connecting the thighbone (femur) to the shin bone (tibia) are:
- Posterior cruciate ligament (PCL): This ligament is in the back of the knee. It controls backward movement of the shin bone.
- Medial collateral ligament (MCL): This ligament gives stability to the inner knee.
- Lateral collateral ligament (LCL): This ligament gives stability to the outer knee.
How Do Knee Ligament Injuries Happen?
Knee ligament injuries can be caused by trauma, such as a car accident or they can be caused by sports injuries. Weak muscles, poor flexibility and control and balance problems can contribute to conditions like tendonitis and knee pain and also put athletes at risk for devastating knee injuries such as ACL tears.
Ligaments that are injured are considered sprains and are graded on a severity scale.
- Grade 1 Sprains: The ligament is mildly damaged and has been slightly stretched but is still able to help keep the knee joint stable.
- Grade 2 Sprains: The ligament becomes loose. This is often referred to as a partial tear of the ligament.
- Grade 3 Sprains: This type of sprain is most commonly referred to as a complete tear of the ligament. The ligament has been split into two pieces, and the joint is unstable.
How Common Are ACL Injuries?
The ACL is one of the most common ligaments to be injured. The ACL is often stretched or torn during a sudden twisting motion. This is when the feet stay planted one way, but the knees turn the other way. Slowing down while running or landing from a jump incorrectly can cause ACL injuries. Skiing, basketball, and football are sports that have a higher risk for ACL injuries.
According to the American Academy of Orthopaedic Surgeons, about half of all injuries to the anterior cruciate ligament occur along with damage to other structures in the knee, such as articular cartilage, meniscus or other ligaments.
What Are Symptoms Of A Tear In The ACL?
When you injure your ACL, you may hear a "popping" noise and you may feel your knee give out from under you. There are other symptoms that you may experience.
- Pain with swelling.
- Loss of full range of motion
- Tenderness along the joint line
- Discomfort while walking
If any of these symptoms occur, you need to see your doctor. Your healthcare provider will ask you your health history and do a physical exam. You also may need one or more of these tests:
- X-ray: This imaging test can rule out an injury to bone instead of a ligament injury. It uses energy beams to make images of internal tissues, bones, and organs on film.
- MRI: This test uses large magnets, radio waves, and a computer to make detailed images of organs and structures within the body. It can often find damage or disease in bones and a surrounding ligament, tendon, or muscle.
- Arthroscopy: This procedure is used to diagnose and treat joint problems. The healthcare provider uses a small, lighted tube (arthroscope) put into the joint through a small cut (incision). Images of the inside of the joint can be seen a screen. The procedure can assess joint problems, find bone diseases and tumors, and find the cause of bone pain and inflammation.
Do ACL Injuries Require Surgery?
Treatment for an ACL injury varies depending on the patient and on your symptoms, age, and general health. It will also depend on how severe the injury to the knee is. ACL treatment may be surgical or non-surgical.
- Nonsurgical treatment: A torn ACL will not heal without surgery. But nonsurgical treatment may be effective for patients who are elderly or have a very low activity level.
- Surgical treatment: The ACL will be reconstructed using tissue from a different part of your body or from a donor and the new ligament will be created to replace the damaged ligament.
Why Do Females Have More Ligament Injuries?
“Women have a statistically greater chance of sustaining a knee ligament injury than a male,” said Frank Eksten, Director of Sports Medicine at Franciscan Health Crown Point.
In the 1980s and 1990s, research focused on dealing with an epidemic of ACL injuries in women athletes.
“Title IX provided women greatly increased opportunities to participate in college sports, so many more women began to participate in higher level athletics,” Ekstein said. “At that time, the training and injury reduction techniques were not as advanced as they are now. As a result, by the mid ’80s we were seeing a large number of ACL injuries in college level women athletes.”
Women’s Knees Are Different
One reason females have more ACL injuries is due in part to differences in women’s anatomy.
The ACL passes through a "notch" in the lower end of the thighbone that forms part of the knee. The ligament is about the same size for a woman as a man—but the notch is up to 20% narrower in women. That makes the woman's ligament more susceptible to tearing.
Muscle Imbalances Set Females Up For Injury
"There tends to be a lot of imbalance in strength in those muscles, which makes them more prone to injury," said Franciscan Physician Network pediatrician Francine Pearce, MD.
A woman's hamstring muscles, at the back of the thigh, are often weak compared with her quadriceps, the muscles at the front of the thigh. The quadriceps pull the bones of the lower leg forward, and the hamstrings pull them back. Hamstring muscles help protect the ACL from injury. When the pulling power is out of balance, the knees suffer.
This muscle imbalance tends to be far worse in women than in men. The imbalance may begin to happen during childhood if girls engage in less physical activity. Exercise can help overcome the problem.
Hormones Impact Ligaments
Hormones also may play a role in ACL injuries. During menstruation, girls release hormones such as estrogen and relaxin. This causes laxity or looseness of the ligaments and makes them more prone to injury. Risk of injury to the ACL appears to be higher during ovulation, when estrogen levels are highest. The ACL appears to respond to estrogen by decreasing cell activity to repair basic ligament fibers called collagen.
According to Dr. Pearce, girls are more likely to tear their ACL than boys and are also more likely to sprain their ankles.
"Don't assume your daughters' coaches know this," Dr. Pearce said. "Parents must be proactive about ensuring their daughters' coaches fully understand these issues."
How Can I Prevent ACL Tears?
Dr. Pearce recommends that girls participate in training that strengthens muscles and stretches their hamstrings. Girls should also take part in agility training where they learn to properly run and shift directions, as well as strengthen their core muscles.
Strengthening exercises are especially important for your hamstrings if muscle imbalances are suspected.
Lying on your belly, draw your lower legs upward, and try to touch your heel to your buttock. Use resistance equal to about 10% of your body weight. Do a few sets of 10 to 15 repetitions; hold them a second or 2.
Jumping exercises are also critical for building strength and preventing knee injuries. When you land from a jump, keep it soft. Come down on the balls of your feet and slowly roll back to the heel. Keep your knees bent and your hips straight. Try to keep your knee in line with your foot.
Hopping over a cone side to side and forward and backward builds strength and control:
- Place a 6-inch cone on your left. Hop over the cone with both feet, concentrating on a soft landing. Repeat by hopping back over the cone to the right. Repeat for a total of 20 hops.
- Place the cone in front of you. Hop over the cone with both feet, then hop backward over the cone. Keep your knees slightly bent when you land. Repeat for a total of 20 hops.
- Repeat the above forward and backward exercise, but hop with 1 leg at a time. Again, keep your knee slightly bent when you land. Do 20 hops on each leg.
By The Numbers
According to SafeKids.org:
- One in three children who plays a team sport is injured seriously enough to miss practice or games.
- Girls are up to eight times more likely to have an ACL injury than boys.
- 62% of organized sports-related injuries happen during practice.
- The most common types of sports-related injuries among children are sprains, muscle strains, bone or growth plate injuries, repetitive motion injuries and heat-related illness.
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