Most people measure blood pressure on their arms, and few people measure blood pressure on their legs. However, in fact, a simple blood pressure monitor can help us detect the health of blood vessels by measuring the blood pressure values in all four limbs. Conditions such as large artery inflammation, fibrosis, atherosclerosis, stenosis, and even occlusion can be detected by measuring blood pressure in the lower limbs.

Blood pressure difference can indicate cardiovascular diseases.

Most people measure blood pressure by rolling up their sleeves and extending their right arm. Although measuring brachial artery blood pressure in the right upper arm is a commonly used method for blood pressure measurement in the majority of people, there are times when it is necessary to measure blood pressure in the lower limbs as well.

In clinical practice, when diagnosing hypertension for the first time, in addition to measuring blood pressure in both upper limbs, I generally recommend measuring blood pressure in the lower limbs simultaneously to make a preliminary judgment on the presence of vascular diseases.

We know that there have been numerous studies indicating differences in blood pressure between the left and right upper arms. Moreover, when these differences reach a certain threshold, they can serve as an indication or a predictor of cardiovascular diseases.

A blood pressure difference of less than 10mmHg between the upper limbs falls within the normal range. However, if the blood pressure difference between the upper limbs exceeds 10mmHg, it suggests the possible presence of vascular diseases, such as arterial stenosis or large artery inflammation on the side with lower blood pressure.

Just like measuring blood pressure in the upper limbs, measuring blood pressure in the lower limbs can also help detect cardiovascular issues. The blood pressure difference between the upper and lower limbs can also be used to predict the risk of certain cardiovascular diseases.

Measuring blood pressure in the lower limbs is important for several reasons.

Under normal circumstances, according to the principle of blood pressure distribution, there are differences in blood pressure between the limbs, with higher blood pressure in the lower limbs compared to the upper limbs.

Generally, the blood pressure in the thigh is about 20-40mmHg higher than that in the arm. However, when the blood pressure in the lower limbs is lower than or equal to the blood pressure in the upper limbs, it often indicates arterial diseases such as atherosclerosis or arterial stenosis in the aorta or femoral artery.

Why does the blood pressure difference between the upper and lower limbs indicate the presence of cardiovascular diseases? This is because when there is occlusive atherosclerosis leading to lower limb arterial occlusion, the blood pressure may not be measurable. Additionally, when thromboangiitis obliterans affects both the upper and lower limbs, the blood pressure on the affected side may not be measurable. In the presence of large artery inflammation, the blood pressure in the upper limbs may not be measurable, or there may be a condition of high blood pressure in the upper limbs and low blood pressure in the lower limbs. By examining blood pressure discrepancies, we can uncover clues related to cardiovascular diseases.

When we discover that the blood pressure in the lower limbs is lower than or equal to the blood pressure in the upper limbs, it is advisable to promptly visit a hospital for relevant examinations such as ultrasound or magnetic resonance imaging (MRI) to accurately assess the condition and take effective measures to prevent more dangerous cardiovascular events.

In addition to examining the difference in blood pressure between the upper and lower limbs, we can also use the ankle-brachial index (ABI), which is the ratio of ankle systolic blood pressure to arm systolic blood pressure, to detect peripheral arterial diseases. Research has shown that a normal ABI value ranges from 1.0 to 1.3, while a value of less than 0.9 indicates lower limb arterial disease. When the systolic blood pressure in the lower limbs is lower than that in the upper limbs, the possibility of aortic arch stenosis should also be considered.

There are two methods for correctly measuring blood pressure in the lower limbs:

Popliteal Artery Measurement: The measurement is usually taken at the popliteal fossa, which is the indentation at the back of the knee where the calf and thigh meet. The cuff should be placed and fastened appropriately (with a snug fit, allowing for one to two fingers to fit underneath). Similar to measuring blood pressure in the arm, before measurement, it is important to remain quiet for 5-10 minutes, avoiding exercise and emotional excitement. The steps for measuring blood pressure in the popliteal artery are the same as measuring blood pressure in the upper limbs.

Ankle Artery Measurement: Place the cuff at the end of the calf, with the lower edge of the cuff approximately 3-4 cm above the ankle, specifically the inner ankle. The measurement method is the same as measuring blood pressure in the upper limbs. Generally, measuring blood pressure in the ankle arteries provides more accurate and reliable results compared to measuring in the popliteal artery. It is a simpler method and considered better for measuring blood pressure in the lower limbs.

It is recommended that individuals above the age of 50 or those with coronary heart disease should include measuring blood pressure in all four limbs as part of routine examinations. Even for healthy individuals, it is advisable to regularly measure blood pressure in the lower limbs in addition to the upper limbs. If there is an absence or decrease in the blood pressure difference between the upper and lower limbs or if it becomes negative, it may indicate peripheral vascular diseases such as large artery inflammation, fibrosis, atherosclerosis, stenosis, or even occlusion.