What is the ACL?
The Anterior Cruciate Ligament, or ACL, is one of the four main ligaments within the knee that connect the femur (thigh bone) to the tibia (shin bone). The ACL is located in the middle of the knee. Its primary function is to provide stability to the knee joint by preventing the tibia from sliding out in front of the femur. It also helps control rotational knee movements and is critical for maintaining balance.
An ACL tear is a tear or stretching of the ligament. There are different types of ACL injuries including:
Grade 1 – the ligament is mildly damaged. It has been stretched but is still able to help keep the knee joint stable.
Grade 2- a partial tear. The ligament stretches to the point where it becomes loose. This is often referred to as a partial tear of the ligament.
Grade 3 – this is the most severe ACL injury. It means a complete tear of the ligament. The ligament has been completely or mostly split into two pieces, and the knee joint is unstable. This is the most common type of ACL tear.
ACL tear symptoms typically include:
- At the time of injury, some people report hearing a loud “pop” or feeling a popping sensation in the knee.
- Immediately following an ACL tear there is intense pain that can make it difficult or impossible to walk or continue the activity that caused the injury.
- Within a few hours after the injury, the knee swells up.
- It may be difficult to move the knee, particularly bending and straightening it.
- The knee area may be very tender to touch.
- Instability makes it impossible to walk as the knee buckles when attempting to bear weight.
Most ACL tears occur during sports that involve sudden stops or changes in direction, jumping, and landing, such as soccer, basketball, football, and skiing. However, an ACL tear can also result from a fall off a ladder or missing a step on a staircase. Ligaments weaken with age and increase the risk of an ACL tear.
ACL injuries often happen as a result of:
- Rapid change of direction such as suddenly slowing down and changing direction (cutting)
- Incorrectly landing from a jump
- Stopping suddenly
- Direct collision or contact, such as a football tackle
- Planting a foot on the ground and a direct hit on a straight or slightly bent leg
Dr. Reynolds will review your medical history and inquire about the circumstances of your injury. He will ask about your symptoms and perform an orthopedic examination checking for swelling and tenderness. He will also perform specific tests that put stress on the ACL, such as the Lachman’s Test, Pivot Shift Test, and Anterior Drawer Test. These tests can help the doctor determine if the ligament is intact or damaged. Imaging studies will be ordered include X-rays to view the bones and rule out fractures, and an MRI which is the most accurate imaging test to diagnose an ACL tear.
With this information he will make a diagnosis, discuss all your treatment options. Treatment options will depend on each patient’s individual needs. For example, a young athlete involved in agility sports will most likely require surgery to safely return to sports, while an older, less active individual might be able to treat the injury with physical therapy and exercise.