Anterior Cruciate Ligament (ACL) Injury
Pronounced: an-TEER-ee-or KROO-shee-ate ligament
Definition |
Causes |
Risk Factors |
Symptoms |
Diagnosis |
Treatment |
Prevention |
Organizations
Definition
An anterior cruciate ligament (ACL) injury is a tear in the ACL ligament. The ACL is located in the middle of the knee joint and connects the shinbone to thighbone.
Causes
Most ACL tears occur during non-contact injuries, such as:
- Planting the foot and cutting
- Pivoting
- Landing on a straight leg
- Making a sudden stop
The ACL can also be injured from a direct blow to the knee.
Risk Factors
A risk factor is something that increases your chance of getting a disease or condition.
- Sex: Female
- Muscle imbalance between the quadriceps and hamstrings (weaker hamstrings)
- Weak quadriceps and hamstrings
- Tight, inflexible quadriceps and hamstrings
- Incorrect technique for cutting, planting, pivoting or jumping
Symptoms
When the ACL tears, you may hear a popping sound. The knee will probably give-way immediately, and it will be difficult to walk on the affected leg. There is usually moderate pain and swelling at the knee joint. This will worsen over the first two days, and then begin to subside.
Diagnosis
The doctor will ask about your symptoms and how you injured your knee, and perform a physical exam.
Tests may include:
MRI scan - a test that uses magnetic waves to show the structures inside the knee joint
Arthroscopy - a thin, lighted tube inserted through a small incision in the knee to look at the structures inside the knee
Treatment
Treatments include:
Knee brace
You may need to wear a knee brace while recovering from your knee injury, as well as when you return to your sport. This may be needed regardless of whether you have surgery to repair the ligament.
Surgery
Surgery may be needed to fully restore function of the knee.
Physical therapy
Range of motion exercises - The therapist will assist you with moving your knee through its full range of motion. Stretching is a part of this treatment.
Strengthening exercises - Due to its lack of use, the affected leg muscles will shrink and lose strength. Therapy will help you regain strength in the leg muscles, especially the quadriceps and hamstrings.
Prevention
Because ACL tears most often occur due to non-contact injuries, precautions can be taken to prevent them.
- When jumping and landing, or turning and pivoting, your hips and knees should be bent, not straight.
- Incorporate adequate warm-up exercises to prepare the knee for your sport.
- Plyometrics, a form of jumping exercises, can be used to train and strengthen the leg muscles for jumping and landing. However, this should only be done under professional supervision if your doctor has determined it is right for you.
- Strengthen both the quadriceps and the hamstrings.
- Keep the quadriceps and hamstrings flexible by stretching regularly.
Organizations
American Orthopaedic Society for Sports Medicine
http://www.aossm.org
American Academy of Orthopaedic Surgeons
http://orthoinfo.aaos.org
SOURCES:
American Academy of Orthopaedic Surgeons
"Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies," Journal of the American Academy of Orthopaedic Surgeons, May-June 2000.
Women, Sport & Performance. Human Kinetics, 1991.
Last reviewed June 2001 by Medical Review Board
