DVT Precautions After Knee or Hip Replacement: What Physiotherapy Covers

A knee or hip replacement is major surgery on a leg, and the first weeks after it carry a real risk of a blood clot forming in the deep veins of that leg. Understanding what your surgical team is already managing, and what physiotherapy specifically contributes to bringing that risk down, is the useful response to that risk. This post covers both, plus the warning signs that mean stop and get medical care right away.

Why joint replacement raises the risk of a blood clot

A blood clot in a deep vein, most often in the calf or thigh, is called a deep vein thrombosis, or DVT. After a total hip or total knee replacement, three things happen together that raise the odds of one forming: blood flow through the leg slows because you are less mobile, the surgery itself causes trauma to blood vessels near the joint, and the body's clotting response ramps up as part of normal healing. The American Academy of Orthopaedic Surgeons (AAOS) names venous thromboembolism, the umbrella term for a DVT and its more serious complication, a pulmonary embolism, as one of the recognized risks after elective hip or knee arthroplasty and the reason both mechanical and pharmacologic prevention are standard practice around these surgeries.

This is a known, planned-for risk, not a surprise complication. Every patient having a knee or hip replaced in BC will have a prevention plan built into their surgical care from before the operation through the first weeks of recovery.

What your surgical team manages medically

Deciding how to prevent a blood clot after your surgery is a medical decision made by your surgeon and the surgical team, not by your physiotherapist. This usually includes a blood thinner, sometimes called an anticoagulant, prescribed at a specific dose and for a specific number of days or weeks. It often also includes compression stockings or a mechanical compression device on the leg, used to help keep blood moving while you are less active.

Your surgeon chooses the type of blood thinner, the dose, and the duration based on your individual risk factors, the surgery performed, and current clinical guidance. Do not stop, start, or adjust a prescribed blood thinner without talking to the surgical team first, and do not assume physiotherapy has any say in that medication. If you have questions about your specific prophylaxis plan, including how long you need to stay on it, that question goes to your surgeon's office, not to your physiotherapist.

What physiotherapy specifically adds

Physiotherapy's contribution to reducing blood clot risk is movement, not medication. The two most consistent tools are getting you walking early and teaching a simple exercise called an ankle pump.

Early mobilization, meaning getting up and walking as soon as the surgical team clears it, is one of the more strongly supported non-drug factors in reducing DVT risk after knee replacement. A study in the Journal of Bone and Joint Surgery (British volume), 2007, compared patients who began walking within 24 hours of a total knee replacement against patients on a more conventional schedule that started rehabilitation on day two. The early mobilization group had a DVT rate of 1.0 percent, compared with 27.6 percent in the later-starting group, and the difference held up after adjusting for other risk factors in the study.

Ankle pumps, a repeated flexing and pointing of the foot at the ankle, work by activating the calf muscle pump, the mechanism that helps push blood back up the leg toward the heart when the leg muscles are not otherwise active. A 2026 meta-analysis of 16 randomized trials in Frontiers in Neurology found that ankle pump exercise added to standard anticoagulant therapy further reduced the risk of postoperative DVT compared with anticoagulant therapy alone, with the clearest benefit from active, patient-performed ankle pumps rather than passive or mechanically assisted versions. The authors rated the overall certainty of that evidence as low, given the size and variability of the trials pooled, which is a reasonable caveat rather than a reason to skip the exercise.

In practice, a physiotherapist teaches ankle pumps in the first physiotherapy contact after surgery, checks that you are doing them correctly and often enough through the day, and progresses your walking distance and standing tolerance on a schedule matched to how the knee or hip is healing. None of that replaces the blood thinner your surgeon prescribed. It works alongside it.

What physiotherapy does not do

A physiotherapist does not diagnose a blood clot, order the imaging test that confirms one, or treat one once it is suspected. If a clot is suspected during a physiotherapy visit, the response is to stop the session and direct you to urgent medical care, not to assess or manage it in the clinic. This is a clear scope line, not a judgment call made case by case.

The same applies to the compression stockings or device your surgical team may have you using. Physiotherapy will check that you are mobilizing well and that swelling is behaving as expected, but decisions about how long to keep a compression garment on, or when to stop it, belong to the surgical team.

Warning signs that need urgent medical attention

Some symptoms after a knee or hip replacement mean stop what you are doing and get medical care immediately, not wait for your next physiotherapy appointment. The Centers for Disease Control and Prevention lists the following as DVT symptoms in the affected leg: swelling, pain or tenderness, warmth, and redness or discoloration. If you notice new swelling, warmth, redness, or calf pain in one leg that is out of proportion to the other side, contact your surgeon's office or seek medical care the same day.

Pulmonary embolism, which happens when part of a clot breaks loose and travels to the lungs, is more urgent. The CDC lists difficulty breathing, chest pain or discomfort that often worsens with a deep breath or cough, a fast or irregular heartbeat, coughing up blood, and lightheadedness or fainting as signs of a pulmonary embolism, and states plainly that anyone with these symptoms should seek medical help immediately. In practice that means calling 911 or going to the nearest emergency department, not calling your physiotherapist or waiting to see if it passes.

How physiotherapy coordinates with your surgical team's precautions

A physiotherapist seeing you after a knee or hip replacement works from the precautions and timeline your surgical team has already set. That includes how much weight you are allowed to put on the leg, how long you are expected to continue a blood thinner or wear compression stockings, and any specific movement restrictions tied to the surgical approach used. Bringing your discharge paperwork to the first physiotherapy visit lets the physiotherapist build the mobilization plan around what the surgeon has already prescribed, rather than guessing at it.

If something looks off during a physiotherapy session, whether that is a leg swelling faster than expected or pain that does not match the healing timeline, the physiotherapist's job is to flag it and direct you back to the surgical team quickly. This is the same coordination model covered in our broader posts on knee replacement prehab and rehab and hip replacement prehab, which walk through the full recovery arc. This post narrows in on the blood clot precaution piece specifically, because it is a medical safety topic that deserves its own explanation rather than a paragraph inside a broader recovery article.

Where to start

If you have a knee or hip replacement booked, ask your surgical team directly what your specific blood clot prevention plan will be, including the medication, the compression garment if one is used, and how long each continues. When physiotherapy starts, whether in hospital or at an outpatient clinic afterward, expect ankle pumps and an early walking plan from the first session, and expect your physiotherapist to check in on how the leg looks at every visit.

If you notice any of the warning signs above, do not wait for your next scheduled visit. Same-day contact with your surgeon, a walk-in clinic, or an emergency department is the right call for leg swelling and redness. Chest pain or shortness of breath is a 911 call.

This article is general information, not personal medical advice. A regulated practitioner can confirm whether the patterns described apply to you.

Frequently asked questions

Does physiotherapy prevent blood clots after joint replacement?

Physiotherapy contributes to reducing the risk through early mobilization and ankle pump exercises, but it works alongside the medical prevention plan your surgeon prescribes, not instead of it. A 2007 study found a large drop in DVT rates in patients who walked within 24 hours of knee replacement compared with those who started later, and a 2026 meta-analysis found ankle pumps added benefit on top of anticoagulant medication. Neither exercise replaces the blood thinner your surgical team prescribes.

Who decides whether I need a blood thinner after surgery?

Your surgeon and the surgical team decide this, based on your individual risk factors and the surgery performed. A physiotherapist does not prescribe, adjust, or advise on stopping a blood thinner. Any question about your medication or how long you need to take it should go to your surgeon's office.

What is an ankle pump and how often should I do it?

An ankle pump is a repeated flexing and pointing of the foot at the ankle, done while lying or sitting. It activates the calf muscle pump that helps move blood back up the leg when you are not walking. Your physiotherapist or the hospital care team will teach you the exact technique and how often to do it, since that detail is set by your specific recovery plan rather than a single fixed number for everyone.

What are the warning signs of a DVT I should watch for at home?

New swelling, pain or tenderness, warmth, or redness in one leg, especially the calf, are the signs to watch for. If you notice these, contact your surgeon's office or seek medical care the same day rather than waiting for your next physiotherapy appointment.

What symptoms mean I should call 911, not just my doctor?

Difficulty breathing, chest pain or discomfort that worsens with a deep breath or cough, a fast or irregular heartbeat, coughing up blood, or lightheadedness and fainting are signs of a possible pulmonary embolism. These require immediate emergency care. Call 911 or go to the nearest emergency department rather than waiting to see if the symptoms pass.

Can I stop my compression stockings once I feel better?

That decision belongs to your surgical team, not to physiotherapy. Compression stockings or devices are usually prescribed for a set period as part of your overall prevention plan, and stopping early should be discussed with your surgeon rather than decided on your own.

Does early walking after surgery increase my risk of falling or hurting the new joint?

Early mobilization after knee or hip replacement is done under supervision and within the weight bearing and movement precautions your surgical team has set, which is different from walking without guidance. The 2007 study on early mobilization and DVT risk found walking within 24 hours reduced clot risk without describing an increase in surgical complications in that early-walking group. Your physiotherapist adjusts the pace and support based on how you are moving that day.

If my physiotherapist notices something concerning during a session, what happens?

The physiotherapist's role in that moment is to stop the session and direct you to urgent medical care or your surgical team, not to assess or treat a suspected clot in the clinic. This is a scope boundary set by physiotherapy's regulator, not a judgment call made case by case.

Sources

• Prevention of Symptomatic Pulmonary Embolism in Patients Undergoing Total Hip or Knee Arthroplasty, Journal of the American Academy of Orthopaedic Surgeons, 2009
• Early mobilisation after conventional knee replacement may reduce the risk of postoperative venous thromboembolism, Journal of Bone and Joint Surgery (British volume), 2007
• Meta-analysis of the effectiveness of ankle pump exercise combined with anticoagulant therapy for the prevention of post-operative lower extremity deep vein thrombosis, Frontiers in Neurology, 2026
• About Venous Thromboembolism (Blood Clots): symptoms and when to seek care, Centers for Disease Control and Prevention
• College of Health and Care Professionals of BC (CHCPBC): regulator of physiotherapists in British Columbia