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. Many people ignore this and hope it will heal on its own. But these could https://www.tumblr.com/medjournalhealthcare/831973505125990400/acl-tear-symptoms-when-do-you-need-surgery