Crossing your legs can contribute to back pain, especially if you do it habitually for long periods. The position tilts your pelvis to one side, which forces your spine out of its natural alignment and creates uneven pressure on the muscles and discs that support your lower back. A few minutes here and there is unlikely to cause problems, but hours of crossed-leg sitting day after day can set the stage for chronic discomfort and postural changes.
How Crossing Your Legs Affects Your Spine
When you cross one leg over the other at the knee, your pelvis rotates and tilts. One hip rises slightly higher than the other, and your lumbar spine curves to compensate. This asymmetric position compresses the spinal discs unevenly and strains the muscles on one side of your lower back more than the other.
Over time, this repeated asymmetry can lead to muscle imbalances that pull your spine further out of alignment even when you’re not crossing your legs. A preliminary study published in the Journal of The Korean Society of Physical Medicine found that sustained crossed-leg sitting causes pelvic tilt that can lead to scoliosis of the vertebral column. The researchers noted that asymmetric sitting postures may eventually cause permanent spinal deformities, including increased curvature of the upper back (kyphosis) and lower back (lordosis), with chronic lower back pain as the end result.
The Piriformis Problem
Your piriformis is a small but powerful muscle deep in your hip that runs from the base of your spine to the top of your thighbone. It’s one of the muscles that rotates your hip outward, which is exactly what happens when you cross your legs. The more time you spend in that position, the shorter and tighter this muscle becomes.
A tight piriformis matters because the sciatic nerve runs directly beneath it (and in some people, straight through it). When the muscle shortens and stiffens, it can compress the sciatic nerve, producing pain, tingling, or numbness that radiates from the buttock down the back of the leg. This is sometimes called piriformis syndrome, and it mimics the symptoms of a herniated disc. People who sit with crossed legs for hours at a desk are particularly susceptible.
Nerve Compression in the Lower Leg
Back pain isn’t the only risk. Crossing your legs at the knee also puts direct pressure on the peroneal nerve, which wraps around the top of your shinbone just below the knee. Compressing this nerve can cause numbness on the top of your foot, tingling or a pins-and-needles sensation in your lower leg, and in more severe cases, difficulty lifting the front of your foot (a condition called foot drop).
For most people, the numbness resolves within minutes of uncrossing the legs. But repeated or prolonged compression can cause more lasting nerve irritation, particularly if you already have conditions that make nerves more vulnerable, like diabetes.
Crossing at the Ankles vs. the Knees
If you find it comfortable to cross your legs and don’t want to stop entirely, where you cross matters. Crossing at the knees or placing one ankle over the opposite knee creates the most pelvic tilt and hip rotation. Crossing at the ankles is a somewhat better option because it doesn’t push the hips and pelvis into as extreme a position. That said, it still isn’t ideal for long stretches, since any asymmetric posture maintained for hours can create imbalances over time.
The best sitting position for your back keeps both feet flat on the floor (or on a footrest), with your knees roughly at hip height and your weight distributed evenly across both sitting bones. If you catch yourself crossing your legs out of habit, simply uncrossing and re-planting your feet can immediately reduce the strain on your lower back.
What About Varicose Veins and Blood Pressure?
Two other health concerns come up frequently alongside leg crossing. The first is varicose veins. Despite the persistent belief, crossing your legs does not cause them. The external pressure from crossing is minimal and not enough to damage your veins. Varicose veins are driven by genetics, age, and weakened valves inside the veins themselves. Crossing your legs can, however, worsen symptoms like swelling or achiness if you already have varicose veins.
The second is blood pressure. Crossing your legs at the knee temporarily raises your blood pressure by 8 to 14 points on the systolic (top number) reading and 2 to 8 points on the diastolic (bottom number). This spike reverses as soon as you uncross. It’s clinically relevant mainly in one situation: if you’re having your blood pressure measured. Sitting with crossed legs during a reading can make your numbers look higher than they actually are, which is why medical guidelines call for both feet flat on the floor during measurement.
Breaking the Habit
Most people cross their legs because it feels comfortable in the moment, often because their core and hip muscles are already fatigued from sitting. The irony is that crossing temporarily relieves discomfort by shifting your weight, but it creates the very imbalances that make upright sitting feel harder over time.
A few practical strategies help. Switching which leg you cross (if you must cross at all) distributes the asymmetry more evenly and prevents one side from becoming significantly tighter than the other. Getting up to move every 30 to 60 minutes gives your hip flexors and piriformis a chance to lengthen. Stretching your hips and glutes regularly, particularly the piriformis, can counteract the tightening that habitual crossing causes. And strengthening your core muscles makes it easier to sit with good alignment without relying on crossed legs for stability.
If you already have lower back pain and you cross your legs frequently, it’s worth treating the habit as a contributing factor. The position alone probably won’t wreck a healthy spine overnight, but combined with long hours of sitting, it adds a layer of asymmetric stress that your back is better off without.