A hematoma, or haematoma, is a collection of blood, generally the result of hemorrhage. Hematomas exist as bruises (ecchymoses), but can also develop in organs.
Hematomas can gradually migrate, as the extravasated cells and pigment move in the connective tissue. For example, a patient who hurts the base of his thumb might cause an hematoma which will slowly move all through the finger within a week. Gravity is the main determinant of this process.
Hematomas on articulations can reduce mobility of a member and present roughly the same symptoms as a fracture.
Types