Entrapment of the lateral femoral cutaneous nerve, diagnosed medically as Meralgia Paresthetica, has been poorly understood. Obesity, pregnancy, and ill-fitting clothing are implicated, citing mechanical compression of the nerve as the cause. Treatment is conservative and usually takes several months to resolve. In a cursory search through the literature, only Travel and Simons in Myofascial Pain and Dysfunction, The Trigger Point Manual identify a different source on pages 230-233. This medical manual is the guidebook for the Neuromuscular Therapy treatments I use to treat difficult chronic pain complaints in my office near Boston.
The last post discussed the role of the sartorius muscle in this condition. More important, in my experience, is a muscle inside the pelvis that is part of the iliopsoas, our most important hip flexor.
The iliacus muscle fills much of the space in the groin at the crease between the thigh and abdomen (look at the illustration in the previous post). The inguinal ligament attaches to the ASIS of the hip bone (ilium) next to the sartorius muscle and crosses the lower abdomen to the pubic bone. Ligaments attach bone to bone and provide a stiff and stable connection with just a little elasticity to prevent fracture at joints. Ligaments are considered “hard tissue” like bone rather than “soft tissue” like muscle. When the iliacus muscle contracts, it can swell and fill the space between the inguinal ligament and the bone of the pelvis that forms a link between the pubic bone and pelvis. That crescent shaped space is called the lacuna musculorum and contains nerves, blood vessels, the iliacus muscle belly and the psoas tendon. When the iliacus muscle contracts to flex the hip, it shortens and hardens forming a muscle bulge (like popeye) that can fill the lacuna and press on the nerves and blood vessels that run through it. The LFC nerve is tucked up in the corner right between the ASIS and the inguinal ligament, two hard tissues. Pressure from the contracted iliacus can trap the nerve and cause the symptoms of Meralgia Paresthetica, among which are burning and numbness in the skin of the outer thigh.
Treatment of the iliacus involves applying sustained pressure using NMT techniques on the muscle in two places, directly on the attachment on the inside of the hip bone (ilium) and in the groin space over the hip joint. Care must be taken by the therapist to avoid pressure on the major blood vessels there which can be clearly palpated by feeling for the pulse. A home program of hip flexor stretches is an important part of relieving the entrapment that causes numbness.
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Nerve entrapment causing numbness and burning on the skin of the outer thigh can be caused by the sartorius and the iliacus muscles. The sartorius muscle attaches to the ASIS (anterior superior iliac spine) at the front angle of the hip bone and travels diagonally across the thigh to the inner knee. To find the ASIS, place your hands on your hips with fingers facing forward so you can feel the curved top of the bone (iliac crest) with your index fingers. Feel for the angled point at the front with your middle fingers. That’s the ASIS to which attaches the sartorius muscle and the inguinal ligament. The lateral femoral cutaneous (LFC) nerve runs just under that attachment point and can sometimes pierce the sartorius muscle as it exits the pelvis. Tension in the sartorius pulls on its tendonous attachment and narrows the space beneath it, trapping the nerve. If the nerve goes through the sartorius, it squeezes it. Either way, entrapment reduces or alters sensation and function causing numbness and weakness. If the nerve gets irritated it causes the burning sensation.
One of my patients who was being treated for low back and butt pain is married to a man who was complaining of burning sensation in his upper and lower leg and hypersensitivity on the skin of his thighs accompanied by numbness on the outside of his thigh and pain and numbness in his butt. He had already had his fourth back surgery and was on very heavy doses of two strong medications because he couldn’t sleep at night without them. His wife was becoming alarmed, especially since she was holistically minded and fearful about possible pain drug addition for him because his symptoms were becoming chronic.
Self-treat your muscles with pressure and massage, ice or heat (ice for pain and muscle spasm 1-5 minutes, moist heat for achiness and stiffness 1-5 minutes. (See my post on Ice or Heat)
Have Trigger Point injections when appropriate (see a physiatrist usually, also medical pain specialists, neurologists and anethesiologists) Dry needling is a good option that doesn’t use an anesthetic.