A blood clot in the leg after surgery is called a DVT, deep vein thrombosis.
It usually shows up as throbbing pain, swelling and warmth in ONE calf or thigh, sometimes with red or darker skin. If it happens, call your surgeon or doctor the same day.
If you have sudden shortness of breath, chest pain that’s worse when you breathe in, or you cough up blood, call emergency services straight away. That can mean a clot has reached the lungs, a pulmonary embolism.
With modern prevention, clots after hip and knee replacement are uncommon: somewhere around 1 to 2 in 100 people get one that causes symptoms.
The risk is highest in the first few weeks and stays raised for up to about three months.
Why surgery raises the risk
- Less movement: your calf muscles normally squeeze blood back up the leg. Lying and sitting a lot slows that down
- The operation itself: surgery and injury make the blood more ready to clot for a while
- Leg surgery in particular: hip and knee replacement, hip fracture surgery and time in a cast or boot for a broken ankle all carry extra risk
- Your own risk factors: a previous clot, cancer, smoking, being overweight, older age, estrogen-containing contraception or hormone therapy, and long journeys all add to it. Tell your team about any of these before surgery
Normal swelling or a clot?
This is the question most people worry about, because swelling after leg surgery is normal. Some patterns help.
- Usually normal: swelling around the operated joint that spreads down the leg, worse at the end of the day and better after a night’s sleep or with the leg up. Bruising that tracks down toward the ankle is common too. It improves week by week. See swelling after knee replacement
- More like a clot: new or worsening pain in the calf, a calf that’s tender when you press it, swelling that doesn’t go down with elevation, warmth, and one leg clearly bigger than the other
- Timing: many clots show up after you’ve gone home, often within the first few weeks, so don’t assume you’re past it once you leave hospital
- You can’t always tell by looking: the signs overlap. An ultrasound scan of the leg gives the answer, so get checked rather than guess
Swelling that eases overnight is usually healing. A calf that gets more painful day by day needs checking.
How clots are prevented
Your surgeon and hospital decide your prevention plan based on your operation and your own risks. Stick to it for as long as they say.
- Blood thinners as prescribed: most people having a hip or knee replacement are given a blood-thinning medicine by tablet or injection. Take every dose and finish the course. In the UK, courses are often around two weeks after knee replacement and around four weeks after hip replacement, but your team may use a different plan
- Moving early: getting up and walking on the day of surgery or the next is one of the best protections you have
- Ankle pumps: point your toes down and pull them up, 10 times every waking hour in the early days. It works the calf pump even when you’re in bed or a chair
- Stockings or leg pumps: compression stockings or inflatable leg sleeves may be used in hospital. If you’re sent home in stockings, ask how long to wear them
- Fluids: drink regularly. Dehydration raises the risk of a clot
- Break up sitting: stand and walk a few steps at least every hour during the day
- Travel: long car trips and flights add risk in the first weeks. Check with your surgeon before you book, and stop to walk often
After a broken ankle or Achilles injury in a cast or boot, some people are given blood thinners too, depending on their risk. Ask if you haven’t been told. See broken ankle surgery recovery.
How long does the risk last?
- Highest: in the first few weeks after surgery
- Still raised: for up to about 90 days, especially if you’re moving less than usual or stuck in a cast
- Falls again: as you walk more and get back to your normal routine
The NHS has a clear page on DVT symptoms and treatment.
For where clots fit in the whole recovery, see hip replacement recovery week by week or knee replacement recovery week by week.
If you do get a clot
A DVT is treated with blood-thinning medicine, usually for at least three months. It stops the clot growing and lets your body break it down. Most people keep walking and doing their exercises during treatment. Your doctor will tell you what’s safe.
Call emergency services if
- You’re suddenly short of breath or struggling to breathe
- You have chest or upper back pain, especially when you breathe in
- You cough up blood
- Your heart is racing, you feel faint or you collapse
Don’t drive yourself to hospital with these symptoms.
Call your surgeon or doctor today if
- One calf or thigh is painful, swollen, warm or tender to touch
- The skin over the painful area looks red, blue or darker than usual
- Leg swelling is getting worse and no longer goes down with the leg raised
- You’ve missed doses of your blood thinner or stopped it early
Mention it at your next review if
- You’re unsure how long to keep taking your blood thinner or wearing stockings
- You’re planning a flight or long drive in the first three months
- You’ve had a clot before or a family member has
Normal swelling gets better as you move, but a clot gets worse, and that’s your cue to call.