Anterior Cruciate Ligament (ACL) Injury
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 lower leg bone to the thigh bone and prevents the leg bone from sliding too far forward at the knee, which would cause instability.
Most ACL tears occur during non-contact injuries, such as:
- Planting the foot and cutting
- Landing on a straight leg
- Making a sudden stop
The ACL can also be injured from a direct blow to the knee.
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
- Playing sports that require sudden changes of direction and deceleration
- Incorrect technique for cutting, planting, pivoting or jumping
When the ACL tears, you may hear a popping sound. When you stand, 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 of the knee joint, although in the first several hours, this may be minor. It will, however, worsen over the first two days, and then begin to subside.
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
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 or not you have surgery to reconstruct the ligament.
Surgery may be needed to fully restore function of the knee, particularly in younger and athletic people. The decision to have surgery should be made after discussion with your doctor about your athletic needs, age, and associated factors.
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 atrophy (shrink) and lose strength. Therapy will help you regain strength in the thigh muscles, especially the quadriceps and hamstrings.
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.