The Full form of ACL is Anterior Cruciate Ligament Injury. ACL injury is the over-stretching or tearing of the Anterior Cruciate Ligament (ACL), one of the major ligaments in the knee. A tear may be partial or complete. ACL injuries most commonly occur during sports that involve jumping and landing, sudden stops or changes in direction such as soccer, football, basketball, and downhill skiing. When an ACL injury occurs, many people hear or feel a “pop” in the knee. The knee may swell, feel unstable and become too painful to bear weight. Depending on the severity of ACL injury, treatment may include rehabilitation exercises and rest to help regain strength and stability or surgery to replace the torn ligament followed by rehabilitation. A proper training program may help reduce the risk of an ACL injury. Signs and symptoms of an ACL injury usually include a loud “pop” or a “popping” sensation in the knee, severe pain and inability to continue activity, rapid swelling, loss of range of motion, a feeling of instability or “giving way” with weight bearing. One should seek immediate care if any injury to knee causes signs or symptoms of an ACL injury. It’s important to get a prompt and accurate diagnosis to determine the severity of the injury and get proper treatment.