ACL Tear Symptoms: When Do You Need Surgery? A Knee injury can happen unexpectedly during sports, exercise, or everyday activities. You hear a "pop." Your knee swells and feels weak. Many people ignore this and hope it will heal on its own. But these could be ACL tear symptoms, https://www.tumblr.com/maheshnadgir/831971012245585920/acl-tear-symptoms-when-do-you-need-surgery?source=share