Blood clots are one of the most dangerous early complications of SCI. A clot in the leg (deep vein thrombosis, DVT) can break loose and travel to the lungs (pulmonary embolism, PE) — a leading cause of death in the first year. The risk is highest right after injury, and it's largely preventable.

Why the Risk Is High

Moving muscles normally pump blood back up your legs. After SCI, paralyzed legs don't pump, so blood pools and can clot — and the body is also more prone to clotting after major trauma. The danger is that you often can't feel the usual pain of a DVT, so it can build silently.

When You're Most at Risk

The danger peaks in the first 2–3 months after injury, which is why hospitals are aggressive about prevention then. Risk drops afterward but never disappears, and it climbs again with anything that adds immobility — surgery, illness, a new fracture, or a long flight or car ride.

Prevention

  • Blood thinners — during the acute period, low-molecular-weight heparin (an injection) is standard; guidelines suggest continuing prophylaxis for at least about 8 weeks, and longer for motor-complete or other high-risk injuries. Follow your team's plan and duration.
  • Mechanical methods — compression stockings and intermittent pneumatic compression ("sequential") devices on the legs.
  • Movement — range-of-motion exercises, early mobilization, and getting upright as able.
  • Hydration.
  • IVC filter — a filter placed in the main vein to catch clots, used in select people who can't take blood thinners.
  • On long travel, ask whether you need extra precautions (see travel).

DVT Warning Signs

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Watch your legs — you may not feel a clot. Signs of a DVT: new swelling (often in just one leg), warmth, redness or discoloration, or a firm/tight calf, sometimes with a low fever. Because pain may be absent, new asymmetric leg swelling is the key sign. Report it to your provider promptly — don't massage the leg. A DVT can also trigger autonomic dysreflexia.

Pulmonary Embolism — Call 911

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A PE is a medical emergency. Sudden shortness of breath, chest pain (often worse with a breath), a racing heart, coughing, lightheadedness, or sudden anxiety/sense of doom — call 911 immediately. A clot that reaches the lungs can be fatal within hours; minutes matter.

What Nobody Tells You

  • No pain doesn't mean no clot. The classic "painful calf" warning often doesn't apply to you — watch for swelling instead, and measure if unsure.
  • Don't stop blood thinners early. The acute prevention window exists for a reason; finish the course your team prescribes.
  • New immobility resets the clock. Surgery, a hospital stay, a bad infection, or a long trip all raise risk again — ask about prevention each time.
  • Sudden breathlessness is never "wait and see." Treat it as a possible PE and get emergency help.

Sources & Further Reading

This page draws on lived SCI experience and published clinical guidance, including:

SCI.help articles are information, not medical advice. Practice varies by injury level, provider, and institution — always confirm specifics with your own care team.

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Based on SCI thromboembolism clinical guidelines and lived experience. Not medical advice. · Last reviewed June 2026