Does a player have to be knocked out to have a concussion?

No. Most concussions happen without loss of consciousness. Being knocked out occurs in fewer than 10% of concussions and is not needed for a concussion to be suspected or diagnosed. However, anyone who loses consciousness because of a head injury has had a concussion.

Concussion can also happen without a direct blow to the head. A knock to another part of the body that makes the head move rapidly (for example a whiplash-type injury) can cause it.

Symptoms usually appear straight away or within minutes, but can be delayed and appear over the first 24-48 hours. Further symptoms such as mood changes, sleep problems or poor concentration may show up over the next few days.