Calf Pain That Isn't a Strain: Blood Clot (DVT) Warning Signs

Your calf has been sore for a couple of days. Maybe you just got back from a long flight, you're a few weeks out from knee surgery, or you've been laid up on the couch with a cast. It feels like a pulled muscle, so you stretch it, ice it and wait.

Most calf pain really is a muscle strain or cramp. But there's one cause that looks a lot like a strain and needs a doctor, not a stretch: a blood clot in a deep vein of the leg, called deep vein thrombosis (DVT).

What is a DVT?

A DVT is a blood clot that forms in one of the deep veins, usually in the calf or thigh. It can partly or fully block blood flow back to the heart, which causes pain and swelling in the leg.

The real danger is that part of the clot can break off and travel to the lungs. This is called a pulmonary embolism (PE), and it can be life threatening. Doctors often group DVT and PE together as venous thromboembolism (VTE).

DVT doesn't always cause obvious symptoms, which is one more reason to take a sore, swollen calf seriously when you have risk factors.

Warning signs to know

Signs of a DVT in the leg include:

• Pain or throbbing in one leg, usually in the calf or thigh, that doesn't settle with rest
• Swelling in one leg, for example one calf or ankle looks bigger than the other
• Warmth over the sore area
• Red, blue or darkened skin around the painful area (this can be harder to see on brown or black skin)
• Swollen veins near the surface
• Pain that gets worse when you stand or walk

Strain or clot: what's the difference?

It can be honestly hard to tell, which is why this is a job for your doctor. But a few clues point more toward a clot than a strain:

• No clear injury. A strain usually starts with a specific moment: a sprint, a jump, a "pop" or a feeling of being kicked in the calf. A clot often comes on gradually with no injury at all.
• Swelling, warmth and colour change in one leg, not just tenderness in the muscle.
• Pain at rest, not only when you push off or stretch.
• A risk factor, like recent surgery, a cast or long travel.

Who is at higher risk?

Your risk of a DVT goes up with:

• Recent surgery or an injury to the legs, hips, belly or brain
• A recent hospital stay, bed rest for 3 or more days, or a leg in a cast or boot
• Long trips sitting in a plane, car or train (over 4 hours)
• Pregnancy, or having given birth in the last 6 weeks
• Birth control pills, patches or rings that contain estrogen, or hormone therapy
• Cancer, heart failure or a previous clot
• Older age, smoking, carrying extra weight, or a family tendency to clot

When to call 911 or go to the emergency department

Call 911 right away if you have leg symptoms like the ones above along with any of these, because they can be signs of a clot in the lungs:

• Sudden shortness of breath
• Chest pain, especially sharp pain that gets worse when you breathe in or cough
• Coughing up blood
• Fainting, a racing or irregular heartbeat, or sudden sweating

Don't drive yourself.

When to see a doctor the same day

If you have a painful, swollen, warm or discoloured calf or thigh but no breathing or chest symptoms, get seen the same day. Call your family doctor and say you're worried about a blood clot. If you can't be seen that day, go to an urgent care centre or the emergency department. If you're pregnant or recently gave birth, contact your doctor, midwife or obstetrics unit.

Doctors use your history, a checklist of risk factors, and often a blood test and an ultrasound to confirm or rule out a DVT. Treatment is a medical decision; don't start or stop any medication on your own. Talk to your doctor or pharmacist.

Why your physiotherapist asks about this

At Vaughan Physiotherapy Clinic, we see a lot of calf strains, Achilles problems and post surgery legs. Because a DVT can look like a strain, we screen for it before we treat. We'll ask how the pain started, whether you've had surgery, a cast, a long trip or a hospital stay, whether you're pregnant or on hormones, and whether you've had any breathing changes or chest pain. We also look at and feel both legs for swelling, warmth and colour change.

A 2022 clinical practice guideline for physiotherapists on blood clots asks physiotherapists to estimate how likely a DVT is whenever someone has leg pain, tenderness, swelling, warmth or discolouration, and to act on it. In practice, that means if a clot is a real possibility, we don't massage, needle, stretch or load that leg. We help you get to your doctor or the emergency department the same day, and call 911 if you have breathing or chest symptoms.

What physiotherapy can and can't do

Physiotherapy can't treat a blood clot. Diagnosis and treatment come from your doctor.

After a DVT has been diagnosed and your medical team has started treatment, physio does have a role. The same guideline supports getting people moving again once they've reached the right level of blood thinning medication, rather than keeping them in bed. Your physio can work with your doctor's plan to help you walk, rebuild strength and get back to normal activities, and keep an eye out for any change that needs medical review.

Key takeaways

• A painful, swollen, warm or discoloured calf with no clear injury may be a clot, not a strain.
• Recent surgery, a cast, long travel, pregnancy and estrogen hormones all raise your risk.
• Call 911 for leg symptoms plus shortness of breath, chest pain or coughing up blood.
• Suspected DVT without breathing symptoms still needs a same day medical assessment.
• Your physio screens for clots before treating calf pain and refers you on if something doesn't fit.

Related reading: You may also find our guides to Baker's cysts and Achilles tendinopathy helpful.

If your doctor has ruled out a clot and it really is a muscle injury, our team can help you get back on your feet. Learn more about calf strains and tears.

Call: 905-669-1221

Visit: 398 Steeles Ave W #201, Thornhill, ON

Book online: vaughanphysiotherapy.com

Sources

Government of Alberta, MyHealth.Alberta.ca. (2024). Deep vein thrombosis. https://myhealth.alberta.ca/Health/pages/conditions.aspx?hwid=aa68134

Hillegass, E., Lukaszewicz, K., & Puthoff, M. (2022). Role of physical therapists in the management of individuals at risk for or diagnosed with venous thromboembolism: Evidence-based clinical practice guideline 2022. Physical Therapy, 102(8), pzac057. https://doi.org/10.1093/ptj/pzac057

NHS. (2026). Deep vein thrombosis (DVT). https://www.nhs.uk/conditions/deep-vein-thrombosis-dvt/

This article is for general information and isn't medical advice. If you have any of the warning signs above, call 911 or contact your doctor right away.