Does Crossing Your Legs Affect Blood Pressure Readings?
Yes, crossing your legs during blood pressure measurement significantly increases both systolic and diastolic blood pressure readings and should be avoided to ensure accurate measurements.
Magnitude of the Effect
The ACC/AHA guidelines explicitly state that keeping legs uncrossed is one of the 7 key strategies for accurate blood pressure measurement, noting that crossed legs bias readings upward and can lead to over-diagnosis and over-treatment of hypertension 1.
Crossing legs at the knee increases:
- Systolic BP by 2-11 mmHg depending on the population studied 2, 3, 4, 5
- Diastolic BP by 2-7 mmHg in most patients 2, 3, 4, 5
The effect is more pronounced in hypertensive patients compared to normotensive individuals 2, 4:
- Hypertensive patients: systolic increases by 6.7-10.5 mmHg and diastolic by 2.3-4.5 mmHg 2, 4
- Normotensive individuals: systolic increases by 2.3-2.7 mmHg with minimal diastolic change 2, 4
Clinical Significance
This magnitude of error is clinically meaningful because it can:
- Misclassify patients into higher blood pressure categories 2
- Lead to unnecessary initiation or intensification of antihypertensive therapy 1
- Result in overestimation of cardiovascular risk 2
The Praxis Medical Insights summary confirms that crossed legs in sitting position increases systolic BP by 2-8 mmHg 6.
Proper Measurement Technique
The American Heart Association guidelines specify that patients should be 1:
- Comfortably seated with legs uncrossed
- Feet flat on the floor
- Back and arm supported
- Arm at heart level (mid-sternum)
The K/DOQI guidelines for dialysis patients similarly emphasize that the patient must be seated quietly for at least 5 minutes in a chair with feet on the floor 1.
Important Distinction: Ankle vs. Knee Crossing
Crossing legs at the ankle does NOT significantly affect blood pressure, unlike crossing at the knee 4. This distinction is important because:
- Only knee crossing produces clinically significant increases 4
- Ankle crossing can be considered acceptable if necessary for patient comfort 4
Mechanism
The blood pressure increase from leg crossing likely results from 2:
- Increased venous return from compression of leg veins
- Increased peripheral vascular resistance
- Isometric muscle contraction
Interestingly, this same mechanism makes leg crossing a useful therapeutic maneuver for patients with orthostatic hypotension to prevent symptomatic blood pressure drops 7.
Common Pitfalls to Avoid
Do not assume small positional changes are insignificant - the ACC/AHA guidelines emphasize that most measurement "errors" including crossed legs bias readings upward and contribute to over-diagnosis 1.
Ensure consistency in measurement technique - leg position should be standardized and documented, as the 2-11 mmHg increase from crossed legs can move patients across treatment thresholds 2, 4, 5.
Remember that multiple factors compound - crossed legs combined with other common errors (unsupported back, arm not at heart level, full bladder) can cumulatively produce even larger inaccuracies 1, 6.