According to the search results, a knock injury is a minor injury or blow to the body, such as a bump, bruise, or scrape. It is usually not as serious as other types of injuries, but it can still be painful and cause discomfort. In sports, the term "knock" might be used to describe a minor injury that doesnt necessarily prevent an athlete from continuing to play. When commentators use the term "knock," its because the player has shown signs of injury, such as muscle spasms or a stretched muscle, after a tackle or other physical impact. In everyday conversation, the term "knock" might be used interchangeably with "injury," but in a medical context, "injury" is often used to describe physical harm that requires medical attention, while a "knock" might be used to describe a minor injury, such as a bruise or scrape.