The Acute phase of an injury is the period of time in between when the injury is sustained, and the beginning of the sub-acute phase. Depending on the severity of injury, and the age and health of the patient, this phase can take up to four or five days. The acute phase is characterised by some or all of the following: immediate pain

Pain

Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

, tenderness, swelling, inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

 and oedema, contour deformity, bleeding

Bleeding

Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood or blood escape from the circulatory system...

, and loss of normal function of the injured area.