WHAT IS AN ANTERIOR CRUCIATE LIGAMENT (ACL) SPRAIN?
A sprain is a joint injury that causes a stretch or a tear in a ligament. Ligaments are strong bands of tissue that connect one bone to another. The ACL is one of the major ligaments in the middle of the knee. It connects the thigh bone (femur) to the shin bone (tibia). The ACL, along with the posterior cruciate ligament, helps to keep the knee stable and protects the femur from sliding or turning on the tibia.
Sprains are graded I, II, or III depending on their severity:
- Grade I sprain - pain with minimal damage to the ligaments
- Grade II sprain - more ligament damage and mild looseness of the joint
- Grade III sprain - the ligament is completely torn, and the joint is very loose or unstable
HOW DOES IT OCCUR?
The anterior cruciate ligament is frequently injured in forced twisting motions of the knee. It may also become injured when the knee is straightened further than it normally can straighten (hyperextended). It sometimes occurs when the thigh bone is forcefully pushed across the shin bone, such as with a sudden stop while you are running or a sudden transfer of weight while you are skiing.
WHAT ARE THE SYMPTOMS?
There is usually a loud, painful "pop" when the joint is first injured. This is often followed by swelling of the knee within the first few hours of the injury. This swelling is called an "effusion" and is made up of blood in the knee joint.
If you have torn your ACL in an injury that occurred months or years ago, and you have not had reconstructive surgery, you may have the feeling that the knee is giving way during twisting or pivoting movements
HOW IS IT DIAGNOSED?
Your doctor will examine your knee, and may find that it has become "loose". If there is swelling in the joint, your doctor may decide to remove the blood in your knee with a needle and syringe. X-rays may be taken to see if there is an injury to the bones in your knee.
An MRI (magnetic resonance imaging) scan may also be done, and should clearly show the condition of your ACL, as well as that of other ligaments and cartilage.
HOW IS IT TREATED?
Treatment includes the following:
- putting an ice pack on the knee for 20-30 minutes every 3-4 hours for 2-3 days, or until the pain goes away
- keeping your knee elevated whenever possible by placing a pillow underneath it until the swelling goes away
- performing the exercises recommended by your doctor or physical therapist
Your doctor may recommend that you:
- wrap an elastic bandage around your knee to keep the swelling from getting worse
- use a knee immobilizer initially to protect the knee
- use crutches
For complete ACL tears, you and your doctor will have to decide if you should have intense rehabilitation, or if you should have surgery followed by rehabilitation. The torn ACL cannot be sewn back together, it must be reconstructed by taking ligaments or tendons from another part of your leg and connecting them to the femur and tibia.
You may consider having reconstructive ACL surgery if:
- your knee is unstable and gives out during routine or athletic activity
- you are a high level athlete, and your knee may be unstable and give out during your sport
- you are a young person who is not willing to give up an athletic lifestyle
- you want to prevent further knee injury (an unstable knee may lead to injuries of the meniscus and to arthritis)
You may consider not having reconstructive ACL surgery if:
- your knee is not unstable or painful, and you are able to do activities of your choosing without symptoms
- you are willing to give up sports that put extra stress on your knee
- you are not involved in sports
If a growing child tears an ACL, the doctor may recommend that surgery be postponed until the child has stopped growing.
WHEN CAN I RETURN TO MY SPORT OR ACTIVITY?
The goal of rehabilitation is to return you to your sport or activity as soon as is safely possible. If you return too soon you may worsen your injury, which could lead to permanent damage. Everyone recovers from injury at a different rate. Return to your activity will be determined by how soon your knee recovers, not by how many days or weeks it has been since your injury occurred. In general, the longer that you have symptoms before you start treatment, the longer it will take you to get better.
You may safely return to your sport or activity when, starting from the top of the list and progressing to the end, each of the following is true:
- your injured knee can be fully straightened and bent without pain
- your knee and leg have regained normal strength compared to the uninjured knee and leg
- the effusion is gone
- you are able to jog straight ahead without limping
- you are able to sprint straight ahead without limping
- you are able to do 45 degree cuts
- you are able to do 90 degree cuts
- you are able to do 20 yard "figure 8" runs
- you are able to do 10 yard "figure 8" runs
- you are able to jump on both legs without pain, and jump on the injured leg without pain
If you feel that your knee is giving way, or if you develop pain or have swelling in your knee, you should see your doctor. If you have had surgery, be sure that your doctor has told you that you can return to your sport or activity.
HOW CAN I PREVENT AN ANTERIOR CRUCIATE LIGAMENT SPRAIN?
Unfortunately, most injuries to the ACL occur during accidents that are not preventable. However, you may be able to avoid these injuries by having strong thigh and hamstring muscles, and maintaining a good leg stretching routine. In activities such as skiing, make sure that your ski bindings are set correctly by a trained professional so that your skis will release when you fall.
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