In the case of a bruise (haematoma), blood from an injured blood vessel leaks into the surrounding tissue. Depending on the depth of the injured blood vessel, the blood collects in the subcutaneous fatty tissue or in the connective tissue around the muscles (muscle boxes). On the thigh, such bruises often occur as a result of injuries and trauma from outside, for example from a blow or from bumping into hard objects.
In these cases one also speaks of a horse kiss. Depending on the extent of the trauma and the size of the injured blood vessel, the bruise on the thigh can take on different sizes and sometimes swell and hurt severely. In most cases, however, bruises on the thigh heal without consequences within two to three weeks. Specialized macrophages in the tissue take up the blood residues and use them.
Bruises on the thigh most frequently occur after a corresponding trauma, i.e. an injury in the affected area. This usually occurs in the context of a blunt violent impact on the thigh, which corresponds to a contusion or bruise. An example would be bumping against the edge of a table or an unfortunate fall onto a hard object.
Bruises are one of the most common consequences of sports injuries. Many sports are conceivable here, such as boxing, football and ball sports in general, or activities at risk of falling, such as skiing or cycling. Operations on the thigh or other medical interventions such as the puncture of a vessel during a cardiac catheter examination can also lead to the injury of vessels and thus to bruising on the thigh.
The above-mentioned causes have in common that the affected persons remember a trauma or injury in the area of the thigh. If such a trauma is not remembered and there is nevertheless (possibly repeatedly) a larger bruise, the doctor must rule out a congenital tendency to bleed (haemophilia). In the case of such a bleeding tendency, so-called minor traumas (e.g. a slight bump) result in large bruises because the blood does not clot. A similar situation is observed in patients taking blood-thinning medication such as Marcumar®. In this case, the dosage of the medication should be checked.
An uncomplicated bruise heals without consequences within two to three weeks, depending on its size. The process takes place in characteristic stages. At first, fresh blood flows into the fat or muscle tissue and the spot appears reddish.
As soon as this blood begins to clot, the stain turns purple to bluish. As the red blood pigment (haemoglobin) is broken down by several enzymes, the bruise first turns brown/black, then green and finally yellowish. If, on the other hand, a bruise hardly improves after two weeks, for example because it is particularly extensive or deep, a doctor should be consulted. In this case it may be necessary to insert a drainage or, in rare cases, to remove the bruise surgically. In this case the body is not able to break down the coagulated blood itself and hardening and remodelling processes in the tissue can occur.