The sensation of a pulse or throbbing in the knee area can be startling, but it is a common experience reflecting normal body function. This feeling is a direct result of blood being pumped through a major blood vessel that passes close to the knee joint. The rhythmic throbbing is the physical manifestation of your heart propelling blood through the circulatory system.
The Anatomy Behind the Pulse
The feeling of a pulse in the knee is directly related to a structure known as the Popliteal Artery. This artery is a continuation of the main blood vessel supplying the leg, the femoral artery, and it is responsible for carrying oxygen-rich blood to the lower leg and foot. It travels through a diamond-shaped space behind the knee called the popliteal fossa.
Because of its location deep within this space, surrounded by muscle and fat, the artery is usually well-protected. However, the Popliteal Artery runs close to the knee joint capsule and the bone surfaces of the femur and tibia. This proximity allows the natural wave of the pulse to sometimes be detected at the skin’s surface, especially when the surrounding tissues are compressed or relaxed.
Common and Benign Explanations
In most cases, a noticeable knee pulse is a non-threatening occurrence resulting from temporary changes in blood flow or body position. Physical exertion, such as vigorous exercise, causes the heart rate to increase and blood flow to become more forceful. This powerful pulse can make the Popliteal Artery’s normal pulsations more pronounced and easier to feel.
Specific body postures can also temporarily increase the pulse sensation. Sitting with the knees deeply bent or in a cross-legged position can slightly compress the soft tissues and the artery itself. This compression may amplify the feeling of the pulse as the blood flow momentarily encounters mild resistance.
States of heightened emotion, such as anxiety or stress, trigger the release of hormones that accelerate the heart rate and increase the force of contraction. This elevated blood pressure and velocity can make pulses throughout the body, including the one behind the knee, significantly more palpable. Individual body composition also plays a role, as people with less fat or muscle tissue in the popliteal fossa may feel the pulse more frequently.
When the Pulse Signals a Problem
While feeling a pulse is normal, a noticeable change in its intensity or a new, persistent throbbing can sometimes signal an underlying medical condition. These conditions represent genuine changes in the artery’s structure or function, unlike benign causes related to temporary blood flow changes.
Popliteal Artery Aneurysm
One concern is a Popliteal Artery Aneurysm, which is an abnormal ballooning or dilation of the artery wall. This weakening can cause a mass that pulses strongly with each heartbeat, and it is the most common aneurysm found in the peripheral arteries.
Hypertension and Entrapment
Severe hypertension, or high blood pressure, may also contribute to a forceful pulse. Chronically elevated pressure means blood is pushed through the arteries with greater force, making the pulse feel stronger than usual. Less commonly, Popliteal Artery Entrapment Syndrome (PAES) affects younger, athletic individuals when an abnormally positioned calf muscle intermittently compresses the artery.
Peripheral Artery Disease (PAD)
Peripheral Artery Disease (PAD), caused by the buildup of plaque, generally leads to a weakened pulse. A doctor may check the popliteal pulse to assess blood flow when PAD is suspected. This is especially true if the patient experiences pain or cramping in the calf during walking, a symptom known as claudication.
Identifying Red Flags and Seeking Medical Advice
A pulsing sensation that is new, persistent, or accompanied by other symptoms warrants a medical evaluation to rule out a vascular issue. If the pulse feels significantly different from your normal pulse, a healthcare provider should assess the change.
Signs that suggest impaired circulation or arterial damage include:
- Persistent pain or throbbing that does not subside with rest or change in position.
- Swelling around the knee or a noticeable lump that pulses, which may indicate an aneurysm.
- A cold sensation, numbness, or tingling feeling in the lower leg or foot.
- Any change in the color of the skin, such as paleness or a bluish tint.