An ACL injury refers to damage to the anterior cruciate ligament, a key ligament in the knee that helps stabilize the joint. These injuries often occur during sports activities that involve sudden stops, jumps, or changes in direction, such as basketball or soccer. Symptoms typically include pain, swelling, and difficulty moving the knee. Treatment for an ACL injury can vary depending on the severity. Mild injuries may heal with rest and physical therapy, while more severe cases might require surgery to reconstruct the ligament. Recovery can take several months, and rehabilitation is crucial for returning to sports safely.