Concussion is a serious brain injury that can occur in both non-contact and contact sports. This injury results from the rapid translational (linear front-to-back, side-to-side) or rotational (angular) movement of the multi-lobular brain within the skull. Such rapid movement can result in damage or disruption of the brain cell structure and metabolism.

Altered brain function may result from this trauma and be expressed in a variety of physical symptoms (e.g., headaches, dizziness, sensitivity to light and sound), physical signs (e.g., loss of balance and coordination), cognitive deficits (e.g., memory and concentration losses) or emotional changes (e.g., depression and irritability). These signs or symptoms may occur immediately after the injury, or onset may be delayed.

The majority of concussions do not result in a loss of consciousness. If a player is suspected of having a concussion, he/she must be removed from the field of play and properly evaluated by a medical professional experienced in concussion diagnosis and treatment.