Venous stasis is the sluggish flow or pooling of blood in the veins of the lower legs, caused by valves inside those veins that no longer close properly. When blood can’t move efficiently back up toward the heart, pressure builds in the leg veins, leading to swelling, skin changes, and, in severe cases, open wounds called venous ulcers. It’s one of the most common vascular conditions, and it tends to worsen over time without management.
How Blood Flow Breaks Down
Your leg veins contain one-way valves, small flaps that open to let blood travel upward toward the heart and snap shut to keep it from falling back down. When those valves weaken, stretch, or lose their shape, blood flows backward (a process called reflux) and pools in the lower legs. This creates persistently high pressure in the veins, known as venous hypertension.
The problem can start in any of three vein systems: the deep veins that run through the muscles, the superficial veins just under the skin, or the perforating veins that connect the two. When the perforating valves fail, high-pressure blood from the deep system gets pushed into the superficial veins, stretching them further and making their valves fail too. It’s a chain reaction that compounds over time. The resting pressure in your leg veins is determined by how well blood drains out, how well the valves hold, and how effectively your calf muscles pump blood upward when you walk.
Risk Factors
A history of deep vein thrombosis (DVT) is one of the strongest predictors. A population-based study found that people who had a DVT faced nearly four times the risk of developing venous stasis in that leg. Left-leg DVT carried the highest risk overall, even for the opposite leg.
Other independent risk factors include older age, higher body mass index, varicose veins, and the length of time since a blood clot event. Each unit increase in BMI modestly raises the odds, possibly because extra weight increases pressure in the central veins. Prolonged standing or sitting also contributes, since gravity works against blood return when the calf muscles aren’t actively contracting.
What It Looks and Feels Like
Venous stasis progresses through recognizable stages. Doctors classify chronic venous disease on a scale from C0 (no visible signs) to C6 (an active ulcer). Knowing where you fall helps guide treatment.
- Early signs (C1–C2): Spider veins or reticular veins appear first. Varicose veins, defined as 3 mm or wider, come next.
- Swelling (C3): Edema develops around the ankle and can extend to the foot and lower leg. It’s often worse at the end of the day and improves overnight. Pressing on the swollen area leaves an indentation.
- Skin changes (C4): The skin around the ankle darkens to a brownish color as red blood cells leak from stretched veins and break down. Stasis dermatitis may develop, presenting as red, scaly, or weeping patches. In more advanced cases, the skin and tissue beneath it become thickened and hardened, a condition called lipodermatosclerosis, which can sometimes tighten the Achilles tendon.
- Ulcers (C5–C6): Venous ulcers typically form on the inner ankle. They appear as shallow, irregularly shaped wounds with a fibrous base. Unlike arterial ulcers, which tend to be deep, dry, and located on the toes or top of the foot, venous ulcers sit in areas of discolored, damaged skin and are surrounded by swelling.
Pain with venous stasis tends to be an aching heaviness that worsens with standing and improves with elevation. Some people also notice itching, cramping, or a feeling of tightness in the lower leg.
How It’s Diagnosed
Duplex ultrasound is the standard diagnostic tool. It combines a traditional ultrasound image with Doppler technology to measure blood flow direction and speed. The test is noninvasive and painless. During the exam, a technician applies pressure or has you perform specific maneuvers to see whether blood flows backward through the valves.
The key measurement is reflux time: how long blood flows in the wrong direction after a valve is challenged. Reflux lasting longer than 0.5 seconds in a superficial vein, or longer than 1.0 second in a deep vein like the femoral or popliteal, is considered significant and confirms the diagnosis.
Compression Therapy
Graduated compression stockings are the cornerstone of venous stasis management. They apply the most pressure at the ankle and gradually decrease toward the knee, helping push blood upward and reducing the pooling that causes symptoms.
For mild swelling or prevention during long workdays, stockings in the 15 to 20 mmHg range are effective. Research on occupational edema found that this level significantly reduced leg swelling within two days. Stockings rated 20 to 30 mmHg provided even greater benefit, particularly for people who sit most of the day. For more advanced disease or active ulcers, higher pressures are sometimes prescribed. The 2023 guidelines from the Society for Vascular Surgery and American Venous Forum reaffirm compression as a core treatment alongside other interventions.
Getting the right fit matters. Stockings that are too loose won’t provide adequate pressure, while stockings that are too tight can be uncomfortable and harder to wear consistently. Most people are measured at the ankle and calf to determine their size.
Leg Elevation and Movement
Elevating your legs above heart level three or four times a day for about 15 minutes at a time helps reduce swelling by letting gravity assist blood return. This is a simple habit that complements compression, especially after long periods of standing or sitting.
Regular walking is equally important. Your calf muscles act as a pump, squeezing the deep veins with each step and pushing blood upward. Sedentary habits weaken this pump and allow pressure to build. Even short, frequent walks throughout the day can make a noticeable difference in symptoms.
Procedural Treatments
When compression and lifestyle changes aren’t enough, procedures can close or remove the damaged veins. Blood reroutes through healthy veins afterward.
Endovenous laser ablation (EVLA) uses heat delivered through a thin fiber inserted into the vein to seal it shut. The procedure takes roughly 45 minutes and is performed under local anesthesia. In a large randomized trial comparing the three main treatment options, EVLA was significantly more effective at closing the target vein than foam sclerotherapy, with success rates more than four times higher at six months.
Foam sclerotherapy involves injecting a chemical foam directly into the vein, causing it to collapse. It’s the fastest option, averaging about 19 minutes, and doesn’t require any incisions. However, it has lower success rates for the main trunk veins and is sometimes better suited for smaller branch veins or as a follow-up to other procedures.
Traditional surgery, which involves physically removing the damaged vein, takes about 50 minutes and had success rates comparable to EVLA. It’s now less commonly used as a first-line option because the minimally invasive alternatives offer similar results with less downtime.
What Happens Without Treatment
Venous stasis is progressive. Untreated, the sustained pressure damages the tiny blood vessels in the skin (a process called venous microangiopathy), leading to the cascade of skin changes described above. The most serious complication is a venous leg ulcer, which can take months to heal and frequently recurs. Ulcers are also vulnerable to infection and significantly affect quality of life. Managing venous stasis early, even with basic measures like compression and elevation, slows this progression and reduces the likelihood of reaching that stage.