Closed head injury has been defined by several authors, but is not agreed upon. The incidence of closed head injury in sports is relatively small, but because the effects may be catastrophic it is an important topic. Forces may be applied to the head from different directions, which results in different types of lesions. The anatomical and physiological changes with head injury have been suggested to explain head injury outcomes. Effects on intelligence and memory have also been reported. Posture had been proposed as a model to examine the subtle effects of head injury. Vision, vestibular input, and somatosensory input are all involved in maintenance of posture. The interaction of these sensory modalities is also pertinent to posture maintenance. Somatosensory input appears to be improperly processed, while vision and vestibular input seem to compensate for lost somatosensation. Attention to regaining the somatosensory component, rather than waiting for compensation to occur, should be addressed in rehabilitation programmes.