Subcutaneous bruising after injury is mainly caused by local capillary rupture and blood pooling, and the specific extent of bruising is closely related to the severity of the injury. After the local smashed injury, the capillaries in the corresponding area will rupture and bleed after being hit by violence, and will be accompanied by edema and oozing of the surrounding tissue, which will lead to the production of subcutaneous bruises. Redness, swelling and bruising will appear on the skin, and the severity of the bruising is closely related to the condition of the trauma and the surrounding tissues. Blood accumulation after trauma will cause bruising, the surrounding tissue is loose, the scope of bruising will be relatively large, but the degree will be relatively light; the surrounding tissue is dense, generally because of blood stasis, can not spread to the surrounding, the scope will be relatively small, but there will be a large hematoma formation. Once obvious pain, activity limitation, should promptly seek medical observation, under the guidance of clinicians standardized treatment.