What causes unexplained bruising on the legs?

Bruising on the legs may indicate underlying medical conditions, particularly when it occurs without trauma. Common causes include coagulation disorders, vascular fragility, or systemic diseases affecting blood vessels.

Vitamin deficiencies, particularly vitamin C and vitamin K deficiency, may increase susceptibility to bruising. Certain medications, such as anticoagulants and corticosteroids, can also contribute to this condition.

In more serious cases, leg bruising may signal hematological disorders such as thrombocytopenia, leukemia, or clotting factor deficiencies. Early medical evaluation is crucial to rule out life-threatening conditions.

If bruising is accompanied by swelling, pain, or frequent recurrence, consulting a physician is necessary. Proper diagnosis enables targeted treatment and prevents complications associated with undetected systemic diseases.

Common Symptoms	– Purple, blue or greenish discoloration of the skin – Tenderness or mild pain – Swelling (sometimes) – Lesions that turn yellow over time
Causes	– Trauma or impact- Use of blood thinners- Blood clotting disorders (hemophilia, thrombocytopenia, etc.)- Vascular wall weakness- Advanced age- Decreased subcutaneous fat tissue
Risk Factors	– Old age- Blood thinners- Bleeding diseases- Obesity- Diabetes- Vitamin deficiencies (vitamin C, K)
Complications	– Development of large hematoma- Infection (rare)- Chronic skin changes
Diagnostic Methods	– Physical examination- Blood tests (coagulation profile, platelet count)- Ultrasound or MRI if necessary
Treatment Methods	– Cause-oriented treatment- Resting and elevating the legs- Applying cold compress- Hematology support if there is a bleeding disorder
Prevention Methods	– Protection from trauma – Careful use of blood thinners – Vitamin support (on doctor’s recommendation) – Regular exercise and healthy lifestyle

Which bruises are dangerous and when to consult a doctor?

First of all, let’s relax knowing that not every bruise is a sign of illness. Small bruises that you notice after a busy day and don’t even remember how they happened are usually harmless. Our body repairs these small damages on its own and the bruise fades within a week or two, changing color (from blue-purple to green-yellow).

However, some bruises are the kind that make you say “I should have this checked by a specialist”. There are some important characteristics that distinguish these bruises from others. If you have one or more of the following bruises on your legs or body, you should consult a physician:

• If you do not remember any bumps, falls or trauma
• If it recurs frequently in different parts of your body
• If the size is much larger than a normal bruise (e.g. the size of the palm of your hand)
• If it takes weeks or even months to heal
• If there is excessive pain, temperature increase and significant swelling in the bruise area
• If you have other complaints in addition to bruises

The last point is particularly important. Some symptoms that accompany bruising on the legs may indicate the seriousness of the condition. These additional symptoms can be:

• Frequent bleeding gums
• Easy onset and prolonged nosebleeds
• Unexplained weight loss
• High fever or night sweats
• Pain and swelling in the joints
• A constant state of fatigue and weakness

Bruising is more common in people taking blood thinners (anticoagulants). However, even in these people, if a sudden change in the number, size or frequency of bruises is noticed, this should be reported to the doctor who prescribed the medication.

Which Problems Causes Spontaneous Bruises on the Leg?

“I didn’t hit anything, but I have a bruise on my leg again.” This is one of the clearest expressions of an underlying health problem. Spontaneous bruises on the body indicate a problem with the blood clotting mechanism or the strength of the vessel wall. The body’s system for preventing and stopping bleeding is complex, and disruption at any point in this system can manifest itself in easy bruising.

The main causes that can lead to this condition are:

Clotting Factor Deficiencies: A genetic deficiency in special proteins (factors) produced in the liver that enable blood to clot. Diseases such as hemophilia fall into this group.

Platelet (Blood Platelet) Problems: Platelets are the first cells to help and form a plug when a blood vessel is damaged. Low numbers (thrombocytopenia) or dysfunctional thrombocytopenia can cause even the slightest leakage to turn into a bruise.

Medicines Used: Blood thinners, anticoagulants such as aspirin, cortisone drugs (thinning the skin), some antidepressants and chemotherapy drugs increase the tendency to bruise.

Liver Diseases: Advanced liver failure, such as cirrhosis, severely impairs the production of clotting factors, leading to widespread bruising.

Chronic Kidney Failure: Insufficient functioning of the kidneys both impairs the function of platelets and weakens the structure of the skin.

Vitamin Deficiencies: In particular, a deficiency of vitamin C, which strengthens the walls of blood vessels, and vitamin K, which is critical for clotting, can cause bruising.

Blood vessel inflammation (vasculitis): This rheumatic condition in which the immune system attacks its own blood vessels, weakening the vessel wall. Vasculitis bruises are usually slightly raised and can be felt to the touch.

Hematologic Cancers Cancers of the blood and bone marrow, such as leukemia or lymphoma, prevent the production of healthy blood cells, especially platelets, leading to severe bruising and bleeding.

What Can Be the Vascular Causes of Bruises on the Legs?

Bruises that are of interest to a cardiovascular surgeon are usually caused directly by disorders in the vascular system itself. These problems can be related to the veins, which carry dirty blood, or the arteries, which carry clean blood.

Why Bruising Occurs in the Legs with Varicose Veins (Chronic Venous Insufficiency)

This is the most common vascular cause of bruise-like symptoms in the legs. The job of the veins in our legs is to work against gravity to carry dirty blood back to the heart. When the one-way valves inside these veins break down, blood cannot be pumped upwards effectively and escapes backwards, accumulating in the legs. This condition is called chronic venous insufficiency or, colloquially, venous insufficiency.

This build-up and increased pressure leads to bruise-like conditions in two ways.

The first is the classic bruise caused by direct trauma. Due to venous insufficiency, the veins close to the skin surface enlarge, swell and become tortuous, forming the varicose veins we all know. The walls of these varicose veins are tense and weak. For this reason, the slightest bump, sometimes even an intense scratch, can easily cause these veins to crack and bleed under the skin, creating a painful bruise.

Secondly, and more importantly, a permanent discoloration, which is not actually a bruise but is often described by patients as a “bruise that does not go away”. The high pressure created by the constant accumulation of blood in the legs (venous hypertension) increases the permeability of the walls of the capillaries, the smallest blood vessels. This causes red blood cells (red blood cells) to leak out of the veins and under the skin. Trapped between tissues, these blood cells break down over time, releasing hemosiderin, an iron pigment. Just like rusting iron, this pigment permanently stains the skin a brown-purple color. This is called hemosiderin staining (stasis dermatitis) and is particularly common on the ankle and lower leg. The presence of this spotting is the most important sign that the disease is now in an advanced stage and the risk of developing hard-to-treat wounds (venous ulcers) in the leg has increased significantly.

Other symptoms of venous insufficiency are also quite typical:

• Increased leg pain at the end of the day
• Swelling in the legs and ankles (edema)
• Feeling of heaviness, fatigue and fullness
• Increased cramps, especially at night
• Skin dryness and intense itching
• Hardening and shine of the skin in advanced stages

If you have these symptoms, the first step in diagnosis is usually a cardiovascular surgery examination followed by a Color Doppler Ultrasonography. This painless and simple test, performed on an outpatient basis, clearly shows which vessels are leaking blood and to what extent, and determines the treatment plan. The aim of treatment is to disable the diseased vessel causing this leakage and to direct the blood to healthy vessels.

Nowadays, these treatments are carried out without large surgical incisions and with modern and comfortable methods. Treatment options include:

Compression Stockings: It slows the progression of the disease and reduces symptoms.

Endovenous Laser Ablation (EVLA): Closure of the diseased vessel from the inside with laser energy.

Radiofrequency Ablation (RFA): Closing the vein by heating it using radio waves.

Biological Adhesive (Cyanoacrylate Closure): Instant closure of the vein by injecting a special medical glue into the vein.

Foam Therapy (Sclerotherapy): Drying method used especially for smaller varicose veins by injecting medication into the vein.

Does Arterial Blockage (Peripheral Arterial Disease) Cause Bruising?

Arteries are vital pipelines that deliver clean blood, rich in oxygen and nutrients, pumped from the heart to the very ends of the body. Risk factors such as smoking, diabetes, high blood pressure and cholesterol lead to calcification and plaque build-up (atherosclerosis) on the inner walls of these arteries over time. These plaques narrow or completely block the vessel, a condition called peripheral arterial disease.

Unlike venous insufficiency, peripheral arterial disease does not directly cause spontaneous bruising. The underlying problem here is much different and more serious: impaired tissue nutrition, i.e. ischemia. In a healthy person, a small bruise caused by a simple bump will heal without any problems thanks to the body’s self-repair mechanism. However, in a leg with a blocked artery, this repair mechanism cannot work because there is not enough blood supply.

This is why a person with peripheral arterial disease cannot heal even a simple bruise caused by the slightest impact. The body cannot send the oxygen, nutrients and repair cells needed to repair the area. Over time, this “non-healing bruise” turns into an open wound, an arterial ulcer. If left untreated, this wound can become infected and progress to tissue death – gangrene. This is a serious condition that can lead to amputation of the leg. In short, in this disease, a “bruise that won’t go away” is actually the beginning of a wound and a danger bell that requires urgent medical attention.

The most important symptoms of peripheral artery disease are:

Walking pain (claudication): It is the most typical symptom. It is a cramp-like pain that occurs especially in the calf muscles when walking a certain distance, and passes after rest.

Resting Pain: When the disease progresses, the person feels severe, burning pain when resting or lying down, especially in the toes and foot. Lowering the leg off the bed temporarily relieves the pain:

• A constant chill and pale color of the feet
• Hair loss on the back of the feet and fingers
• Thickening, dulling and deformities in toenails
• Weak or absent foot pulses on palpation

The diagnosis is based on a simple ankle-brachial pressure index (ABI) measurement and Color Doppler Ultrasonography. The aim of treatment is to open the blocked vessel and restore blood supply to the leg. Treatment options include control of risk factors, drug therapies, non-surgical angiographic methods (balloon, stent) and surgical bypass (bridging) operations.

Is Leg Bruising Common Among Leukemia Symptoms?

Yes, unfortunately, the symptoms of leukemia can often manifest themselves in the form of bruising on the leg and this is one of the most important early signs of the disease. Leukemia, cancer of the blood, is a disease of the bone marrow, the factory where blood cells are produced. In this disease, abnormal cancer cells fill the bone marrow uncontrollably, leaving no room for the production of healthy blood cells.

One of the first and most affected cells is platelets, which are responsible for stopping bleeding. When the platelet count drops to dangerous levels (thrombocytopenia), the body’s bleeding control mechanism is disrupted. As a result, a person may bruise excessively even at the slightest impact, and sometimes even without any trauma, spontaneously develop bruises on the legs, arms or torso.

Symptoms of bruising and bleeding due to leukemia usually show some typical features:

Petechiae: Rashes in the form of small pinhead-sized, red-purple dots that are not raised from the skin surface, especially on the lower parts of the legs. This is a very typical sign of low platelets.

Bleeding Gums and Nosebleeds: Easy and prolonged bleeding, even when brushing your teeth, or frequent recurrent nosebleeds are important symptoms.

Common and Unexplained Bruises: Bruises can be seen not only on the legs but also on areas that are not normally hit, such as the back and abdomen.

Other Systemic Symptoms: Leukemia is not only characterized by bleeding. In addition to bruises, the following complaints are also common:

• Extreme fatigue due to anemia, shortness of breath on exertion and pale skin color
• Frequent fever and infections because the body’s defense system is weakened
• Significant and involuntary weight loss
• Sweating at night to the point of wetting the bed or clothes

If bruising on your legs is accompanied by such deterioration in your general health, this should not be ignored and you should consult an Internal Medicine or Hematology (Blood Diseases) specialist immediately. A simple complete blood count (hemogram) test can quickly detect abnormalities in blood cells.