Causes of Bruises
Most foot bruising is caused by a minor trauma or injury--from bumps, dropping something on your foot, scrapes, trips or falls, sports injuries, sprained ankles or even just walking, running or jumping on hard surfaces. A bruise forms when blood vessels near the surface of the skin break, allowing a small amount of blood to leak into the tissues under the skin.
Easy bruising may simply be a familial, or inherited, tendency and not necessarily a cause for concern. Easy bruising, often called “purpura simplex,” also can happen because of age, gender (women bruise more easily than men) and lifestyle factors, such as alcohol abuse (which decreases blood clotting), obesity or simply wearing the wrong size shoes or improperly designed or fitted shoes. However, frequent and unexplained bruising on your feet (or any part of your body) can be a sign of something more serious, such as a blood clotting disorder or a blood disease.
Foot bruises are classified as “contusions,” “hematomas” or “purpura” based on the nature and severity of the injury.
Contusions are caused by any blow--from mild impact to serious blunt-force trauma--that damages and breaks open the blood vessels in the tissues of the skin, muscles or bones, Contusions may be accompanied by pain and swelling. Foot bone contusions and deep muscle contusions can be very painful and take longer to heal than contusions that only affect the skin tissues.
Hematomas are a type of bruising in which significant bleeding results in blood pooling under the skin at the site of injury. Hematomas can be caused by the same forces that cause contusions, but they generally cause more pain, swelling and complications. Hematomas can also be caused by surgical procedures or the spontaneous rupture of a blood vessel. Common hematomas affecting the foot include subcutaneous hematomas (collection of blood beneath the skin) and subungal hematomas (collection of blood under a toenail).
Purpura is caused by spontaneous leaking of blood from tiny blood vessels (capillaries). It results in red, flat spots or patches on the skin and mucus membranes. Purpura that results in tiny spots on the skin is called “petechiae.” A large area of purpura is called “ecchymosis” (although any type of bruising of the skin is often referred to as “ecchymosis”).
Purpura is not caused by trauma, as are contusions and hematomas, but by a variety of diseases, disorders and conditions including autoimmune diseases such as lupus, rheumatoid arthritis; certain infectious diseases such as meningitis, mononucleosis, Rocky Mountain spotted fever and measles; certain medications, such as aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), antibiotics, antihistamines and anticoagulants (blood thinners); insect bites; leukemia; thrombocytopenia (low platelet count that causes problems with clotting); and vasculitis (blood vessel inflammation).
A bone bruise, by contrast, is much more painful than a bruise on the skin or in the muscle, and the pain lasts much longer . A bone bruise is considered to be one step below a fracture. Human bone is made up of interconnected fibers. When only a few fibers break but the bone does not break, a bone bruise results. If enough fibers break, the result is a fracture.