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HealthInfo Waitaha Canterbury

Deep vein thrombosis & plaster casts

Tepe ia-auraki hōhonu me ngā tākai ukutea

Leg in castA DVT is a blood clot that forms in a vein deep in your leg. This blocks the normal flow of blood through your leg and can cause pain and swelling. Sometimes part of the DVT can break off and travel to your lung. This is called a pulmonary embolism (PE), which can be dangerous.

Being in a plaster cast slightly increases your risk of a DVT. This is because you aren't moving around as much as usual, so you have reduced blood flow. Surgery and broken bones can also add to this risk because they can cause changes in your blood vessels.

Other things that can increase your risk of DVT include:

  • recent long-haul travel
  • cancer
  • pregnancy
  • smoking and obesity.

Tell your doctor or nurse if you have any of these risk factors so they can decide if you need to be treated to reduce your risk of a clot.

Symptoms of a DVT with a cast

A DVT typically causes pain, a tender calf, swelling in the affected leg and sometimes redness.

If you've been injured and your leg is in a cast, some swelling is normal. But if you think the swelling is increasing despite keeping your leg raised or if the pain is increasing even though you're taking what should be enough pain relief, contact the Orthopaedics Outpatients Department (OOPD). Or you can make an appointment to see the OOPD, your follow-up fracture clinic, your GP or the Emergency Department.

If your leg swells a lot after the plaster cast is taken off, it's also important to see a doctor.

Reducing your risk of a DVT with a cast

Your doctor will let you know if you're at a high risk of developing a DVT and need medication to help prevent it.

If you have any concerns about your injury or plaster cast, phone the clinic that first treated you, the Orthopaedics Outpatients Department or see your GP.

Written by Orthopaedics Outpatients Department, Canterbury DHB. Adapted by HealthInfo clinical advisers. Last reviewed February 2022.

See also:

Deep vein thrombosis in the lower limb


Page reference: 132033

Review key: HILWI-174362