Thigh Pain (Meralgia Paresthetica) Overview

People describe the sensations of meralgia paresthetica in various ways—tingling, pins and needles pricking, the sensation of a cell-phone vibration, or a badly sunburned feeling.

Meralgia paresthetica, which affects 32 out of every 100,000 people, is one cause of thigh pain. The symptoms include anything from a searing burning pain to numbness in the front and side of the thigh. The pain feels very superficial, and the skin on the affected leg feels different to the touch compared to the other side. The sensations can vary from week-to-week, and the symptoms rarely extend below the knee.

The Lateral Femoral Cutaneous Nerve

The culprit inside your body zapping you with thigh pain has a long name—the lateral femoral cutaneous nerve. As a sensory nerve, its job is not to move your leg, but instead to tell you if a soccer ball is hitting your thigh, an insect is crawling over your thigh, or to sense if your thigh is otherwise being touched or burned. Originating in the spine, the nerve traverses over bones, then through muscle, ligaments, and fat to reach your thigh skin, where it performs its mission of converting tactile cues into electrical messages that it sends back to the spine and up to your brain.

The nerve encounters challenging bodily geography along its path from your spine to your leg, however, as it must summit the mountainous iliac crest of your pelvis, tunnel through the sinewy psoas muscle, leap over the bony ski-jump-like protrusion of the anterior superior iliac spine, weave through the inguinal ligament in your groin, and finally emerge out through fat layers to your skin. Interestingly, not everyone’s lateral femoral cutaneous nerve takes the same path from their lumbar spine to their thigh skin. Nor does it branch in the same areas. Scientists dissecting cadavers noted the peculiar differences in the branching pattern and locale of this nerve even in the 1800s.

Source: 123RFThe high blood sugar levels of those with undiagnosed or untreated diabetes can make nerves more vulnerable to injury, as well as those with hypothyroidism.

What Causes Meralgia Paresthetica?

No matter how your nerve travels or branches, anywhere along its route that the nerve gets pinched, it can cause a burning, tingling, or numbness in the thigh. Around 150 years ago, it was tight corsets that pinched the nerve against the hip bone. Today, a utility belt, military pack equipment or tight jeans might cause the same symptoms of pain or numbness. Or, if the nerve is getting pinched farther down by the inguinal ligament in your groin, it might be because a cellular phone in your pocket is compressing it. Cyclists have reported the pain, as well as those who are obese and have a layer of abdomen hanging against the pelvis and compressing the nerve. Seat belt injuries during a car accident can irritate the nerve as well.

A 2018 study showed that almost one-fourth of patients placed face-down in an operating room on a certain frame for posterior spine surgeries lasting longer than 3.5 hours had meralgia paresthetica as the nerve got pinched between the frame and a ligament or bone.

Besides the nerve getting pinched by forces from the outside, internal forces can also add pressure to a nerve, like that of a growing baby during pregnancy, a tumor, or scar tissue. Certain surgeries, like those that involve harvesting bone for grafting from the iliac crest of your pelvic bone, may lead to inadvertent damage to the lateral femoral cutaneous nerve, resulting in the telltale thigh pain. Other surgeries where the lateral femoral cutaneous nerve is at risk for damage include spine procedures, hip replacements, pelvic osteotomies, bariatric surgery, aortobifemoral bypass, and significantly, laparoscopic hernia repairs. One study reports that cases of meralgia paresthetica are up 5% after laparoscopic hernia repair cases using the theoretically minimally invasive instruments in comparison with open incision hernia repairs.

In addition to mechanical injury, there are a few other internal abnormalities that might make a person more susceptible to meralgia paresthetica. The high blood sugar levels of those with undiagnosed or untreated diabetes can make nerves more vulnerable to injury, as well as those with hypothyroidism, or whose bodies are prone to inflammation thanks to lead poisoning or alcoholism.

Updated on: 03/13/19
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Thigh Pain (Meralgia Paresthetica) Diagnosis
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