Uterine fibroids are non-cancerous growths that develop in or on the wall of the uterus, affecting many women during their reproductive years. While often asymptomatic, fibroids can cause symptoms like heavy bleeding, pelvic pressure, and discomfort. Fibroids can also cause pain that radiates into the legs. This leg discomfort is not a direct symptom of the fibroid tissue itself, but a consequence of the fibroid’s size and location within the confined space of the pelvis. The mechanical pressure exerted by these growths on neighboring structures is the direct cause of referred leg pain.
The Mechanical Connection: How Fibroids Cause Leg Pain
The pelvis is a dense anatomical region containing the uterus, major nerves, and large blood vessels that extend down into the legs. As a fibroid grows, it displaces and presses against these structures, which is the primary mechanism for leg pain. This pressure manifests in two distinct ways: nerve compression or vascular compression, each causing a different type of discomfort.
Nerve compression most often involves the sciatic nerve, which runs from the lower back through the hips and buttocks and down each leg. When a fibroid, particularly one located on the back of the uterus, enlarges, it can press directly on the sciatic nerve or its nerve roots. This pressure causes sharp, shooting, or radiating pain, often described as sciatica, which travels down the leg and may include tingling or numbness. Fibroids may also compress other pelvic nerves, such as the obturator or femoral nerves, leading to pain or weakness in the thigh or hip.
The second major mechanism is vascular compression, where the fibroid presses on major veins returning blood from the legs to the heart. The iliac veins and the inferior vena cava are vulnerable to this external pressure due to their proximity to the uterus. Compression of these vessels slows blood flow, leading to venous congestion. This congestion is experienced as a dull, heavy ache, swelling, or a feeling of fullness in the legs. Reduced blood return can also increase the risk of developing a deep vein thrombosis (DVT).
Specific Fibroid Characteristics Leading to Leg Discomfort
The risk and severity of leg discomfort depend less on the total number of fibroids and more on their specific characteristics, such as location and volume. Subserosal fibroids, which grow on the outer surface of the uterus, are the most common cause of pressure-related symptoms. If these growths are situated on the posterior wall, they are directly positioned to compress the nerves and vessels against the bony structures of the pelvis.
Fibroids that grow downward into the cervix or those located within the broad ligament also pose a high risk because of their close proximity to the pelvic neurovascular bundles. A fibroid does not necessarily need to be exceptionally large to cause symptoms if it is strategically located in a confined space. Even a moderately sized fibroid in a high-pressure zone can be more symptomatic than a much larger one growing in a less sensitive area. Pedunculated fibroids, which are attached to the uterus by a stalk, can also cause external pressure if they press against nearby structures.
Addressing Fibroid-Related Leg Pain
For individuals experiencing leg pain suspected to be related to fibroids, the initial step involves confirming the connection through diagnostic imaging. An ultrasound can visualize the size and location of the fibroids, but a magnetic resonance imaging (MRI) scan offers a more detailed view. The MRI assesses the precise relationship between the fibroids and the major nerves and blood vessels in the pelvis, helping to rule out other causes of leg pain.
Treatment for this discomfort focuses on reducing the size of the fibroid to relieve the physical pressure on surrounding structures. Hormonal therapies, such as Gonadotropin-Releasing Hormone (GnRH) agonists and antagonists, can temporarily shrink fibroids and reduce pressure-related symptoms. A minimally invasive option is Uterine Fibroid Embolization (UFE), which blocks the blood supply to the fibroid, causing it to shrink significantly and alleviate pressure on nearby nerves and veins. Surgical options include a myomectomy, which removes only the fibroid while preserving the uterus, or a hysterectomy, the complete removal of the uterus, which provides a definitive solution for eliminating the source of compression.