ACL Tear Symptoms: Signs, Treatment And When Surgery Is Needed 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 https://app.notion.com/p/ACL-Tear-Symptoms-When-Do-You-Need-Surgery-40a3e2528ece80589950e1ea9dcfd1b0?source=copy_link