Mayo Clinic | American Hospital

Anterior cruciate ligament injury

Last Updated on August 14, 2026

Description

A tear or sprain of the anterior cruciate ligament in the knee.

Overview

An anterior cruciate ligament (ACL) injury is a tear or sprain of one of the main ligaments in the knee. The ACL connects the thigh bone to the shinbone at the knee. Most ACL injuries happen during sports such as soccer, basketball, football and downhill skiing.

Symptoms

Symptoms include knee swelling, instability and pain when standing. People often hear or feel a pop in the knee when the injury happens.

Treatments

Treatment for ACL injury depends on how serious the injury is and the stability of your knee. Treatment may include surgery and physical therapy.

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