Understanding ACL Tear Symptoms And the Need for Surgery A sudden knee twist while playing sports, running, or walking can cause a serious injury. You hear a "pop." Your knee swells and feels weak. Some people assume the injury will improve without treatment. But these could be ACL tear https://app.notion.com/p/ACL-Tear-Symptoms-When-Do-You-Need-Surgery-40af0ffaeda780df9581ce8be7f83a8a?source=copy_link