ACL Injury: Symptoms, Causes & Treatment

The anterior cruciate ligament is one of the main ligaments inside the knee joint, playing an important role in stabilizing the joint, preventing the shin bone from sliding forward, and controlling rotational movements. Injury to this ligament (a complete or partial tear or a sprain) is among the most common and important knee injuries, especially among athletes, and may greatly affect the knee's stability and function.

An ACL injury often occurs during sports activities requiring quick direction changes (cutting), sudden stopping, jumping and landing improperly, sudden twisting of the knee, or receiving a direct blow to it. The characteristic sign of many of these injuries is hearing or feeling a popping sound in the knee at the moment of injury, followed by severe pain, rapid swelling within hours (due to bleeding inside the joint), difficulty continuing the activity, and a feeling that the knee is unstable, gives way, or slips when trying to walk or turn. An ACL injury may be accompanied by other knee injuries such as a meniscus tear.

Evaluation begins with a careful clinical examination of the knee and stability tests, and the diagnosis is often confirmed by MRI that shows the ligament and accompanying injuries. Treatment depends on several factors: the severity of the tear, the presence of other injuries, and the patient's age, activity level, and sports goals. Initially the acute injury is managed with rest, ice, compression, limb elevation, and painkillers to reduce swelling. Then treatment is either conservative, relying on an intensive physical therapy program to strengthen the muscles around the knee and restore its stability and function (suitable for some less active patients or partial tears), or surgical by reconstructing the ligament (especially for athletes, active young people, and those with recurrent instability), and surgery is followed by a long, systematic rehabilitation program. It is important not to return to sports before completing rehabilitation and restoring strength and stability, to avoid re-injury.

• A popping sound in the knee at the moment of injury.
• Severe pain and rapid swelling within hours.
• A feeling of knee instability or giving way when walking or turning.
• Difficulty continuing the activity.

• Quick direction change (cutting) or sudden stopping.
• Improper jumping and landing or sudden twisting of the knee.
• A direct blow to the knee, especially in sports.

• Clinical examination of the knee and stability tests.
• MRI to confirm the tear and accompanying injuries.
• Assessing the meniscus and other ligaments.

Initial management

• Rest, ice, compression, limb elevation, and painkillers to reduce swelling.

Conservative treatment

• An intensive physical therapy program to strengthen the muscles and restore stability (for some patients or partial tears).

Surgical treatment

• Ligament reconstruction (especially for athletes, the active, and those with recurrent instability) followed by long, systematic rehabilitation.

Do not return to sports before completing rehabilitation. This content is educational and does not replace consulting an orthopedic specialist.

• Chronic knee instability.
• Meniscus tear and accompanying injuries.
• Early joint arthritis in the long term, and re-injury with early return to sports.

• Exercises to strengthen the thigh muscles and training on correct jumping and landing.
• Good warm-up and proper movement techniques in sports.
• Not returning to sports before completing rehabilitation and restoring strength and stability.