Crossing your legs temporarily raises blood pressure, compresses a nerve near your knee, and shifts your pelvis and spine out of alignment. Whether these effects cause lasting harm depends mostly on how long and how often you sit this way. Here’s what actually happens in your body when you cross your legs, and what’s worth worrying about.
It Raises Your Blood Pressure Immediately
When you cross one ankle over the opposite knee, your systolic blood pressure (the top number) rises by about 11 mmHg and your diastolic (the bottom number) rises by about 4 mmHg. Heart rate, stroke volume, and cardiac output all increase as well. These changes happen right away and reverse once you uncross. Crossing at the ankles, by contrast, has no measurable effect on blood pressure.
For most people, this temporary spike is harmless. But if you already have high blood pressure or are having your blood pressure measured at a doctor’s office, crossing your legs can produce a misleadingly high reading. That’s why clinical guidelines specifically instruct patients to keep both feet flat on the floor during a blood pressure check. If you’ve ever been told your reading was borderline high, it’s worth asking whether your legs were crossed at the time.
Nerve Compression and “Foot Drop”
A nerve called the common peroneal nerve runs just below the surface near the bony bump on the outside of your knee. When you cross your legs, the top leg presses directly against this area on the bottom leg. Hold that position long enough and the nerve gets compressed, which is what causes that familiar tingling or numbness in your lower leg and foot.
In most cases, uncrossing your legs restores feeling within seconds or minutes. But prolonged or habitual leg crossing can cause a more serious condition: peroneal nerve palsy. This shows up as “foot drop,” where you lose the ability to lift the front of your foot, making it difficult to walk normally. In a study of patients with posture-induced peroneal nerve palsy, habitual leg crossing while seated was one of the most common triggers. Most patients first noticed tingling (63%), numbness (27%), or a burning sensation (10%) before the foot drop developed, so those early warning signs are worth paying attention to.
Pelvic and Spinal Misalignment
Crossing your legs forces one hip into a flexed and rotated position, which tilts your pelvis unevenly. Research measuring the effect of crossing the right leg over the left found that the right side of the pelvis rotated backward compared to the left, creating a measurable twist. That pelvic rotation then travels up the spine, producing a subtle lateral curve: concavity on one side, convexity on the other.
A key threshold appears to be around three hours per day. A study comparing posture changes across different durations of leg crossing found that people who sat cross-legged for more than three hours daily developed shoulder tilting, lateral pelvic tilt, and forward head posture. Below that threshold, the effects were less pronounced. So occasional crossing during a meeting or a meal is a very different situation from spending most of your workday with your legs stacked.
Effects on Muscles and Low Back Pain
Crossing your legs puts your hip muscles into an asymmetric position. The top leg sits in flexion and adduction (pulled inward), which lengthens some muscles and shortens others. Over time, this can alter muscle strength and activation patterns on both sides of your hips and trunk.
Interestingly, crossing your legs does offer a short-term payoff: it reduces activity in your core stabilizing muscles (the obliques) and compresses the sacroiliac joints, which temporarily feels more stable and less fatiguing. That’s why it feels comfortable. The trade-off is that people with low back pain who sit cross-legged tend to adopt a more slumped, kyphotic posture because their trunk control is already reduced. The crossed position essentially lets those stabilizing muscles check out even further, reinforcing the poor posture rather than correcting it.
It Doesn’t Cause Varicose Veins
This is one of the most persistent myths about leg crossing. Varicose veins result from a structural problem with the veins themselves, specifically faulty valves that allow blood to pool. Crossing your legs does not cause this. Standing for long periods may aggravate veins that are already damaged, but the same logic applies: the underlying problem has to exist first. If varicose veins run in your family or you already have them, leg crossing isn’t making them worse in any meaningful way.
What About Blood Clots?
Deep vein thrombosis (DVT) is a concern with prolonged immobility, such as during long flights or hours of desk work without movement. Crossing your legs doesn’t appear to be a specific, independent risk factor for DVT. The real issue is sitting still for extended periods regardless of leg position. Blood flow slows whenever your legs are stationary and bent at the hip and knee, whether crossed or not. The fix is the same either way: get up and move regularly.
How to Sit if You Habitually Cross
You don’t need to eliminate leg crossing entirely. The research points to duration and frequency as the real problems, not the position itself. Keeping total crossed time under three hours a day appears to prevent the postural shifts that lead to shoulder tilting, pelvic imbalance, and forward head posture.
If you catch yourself crossing, switch sides periodically so neither hip stays in the same asymmetric position for long. When you’re working at a desk, keeping both feet flat on the floor (or on a footrest if the chair is too high) is the most neutral position for your pelvis and spine. And during any blood pressure reading, uncross your legs and plant both feet to get an accurate number.
The tingling and numbness that come from nerve compression are your body’s clearest signal. If you feel pins and needles, that’s the peroneal nerve telling you to shift. Most people instinctively uncross at that point, but if you’re deeply focused or tend to ignore the sensation, it’s worth building the habit of responding to it promptly, especially if you notice tingling becoming a regular occurrence.