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.