Compression of the the Lateral Femoral Cutaneous Nerve can cause a tricky problem called meralgia paresthetica ( called paraesthetica in the UK). This little known problem causes leg pain and numbness in the thigh, usually in a defined oval patch.
Because it's uncommon it is often overlooked or confused with femoral or sciatic pain or other nerve root impingements. During my career I have been referred patients with a diagnosis of sciatica or femoral nerve irritation and its turned out to be this – not hundreds but still a significant number.
Lateral femoral cutaneous nerve - showing the defined oval area of sensory loss
Meralgia paresthetica (paraesthetica in the UK) is caused by irritation of the lateral femoral cutaneous nerve. The lateral femoral cutaneous nerve is a branch of the femoral nerve. It starts its life arising from the 2nd and 3rd lumbar nerve roots in the lower back. These nerve roots bundle together to form this nerve. The lateral femoral cutaneous is a sensory nerve, which means it delivers messages about sensation or how something feels to the brain. The area it delivers messages about is the outer aspect of the thigh.
Sometimes, along its course the nerve can become restricted or compressed. If the restriction is severe then the nerve can develop a loss of function and can give rise to symptoms of pain and numbness in the thigh, usually in a very clearly defined oval patch. It’s the neatness of the numbness that gives the diagnosis away, you can often literally draw a line where normal sensation ends and the numbness in the thigh begins and this follows the pattern seen to the left here.
The problem arises in the groin where the nerve passes close underneath the inguinal ligament. See the diagram below.
Meralgia Paresthetica and the relationship between the lateral femoral nerve and the inguinal ligament - see how close to the ligament the nerve passes.(image courtesy Grays anatomy)
Any increased compression in this small area can lead to problems. Things that can increase the pressure include:
The best treatment is to find and remove the cause of the compression. By losing weight and getting more comfortable clothing you can sometimes reduce the symptoms. It is occasionally helpful to stretch the front of the hip as shown in the stretches below:
|Front of hip stretches|
|Lie on your back close to the edge of a bed or firm surface- hug both knees tightly to your chest and then firmly keeping hold of one leg , let the other gently drop. You should feel a stretch at the front of your hip on the leg that is down. Do not let your back arch as this may be sore if you have lower back pain.||Kneel and step forward with the side to be stretched behind you. Feel a gentle stretch at the front of the hip.|
This is not specific advice and it may not be suitable for you so make sure you have talked your treatment over with your own health care provider before trying any of these stretches.
If this fails to work then sometimes a medical or surgical option will be considered.
The hardest thing about this problem is getting the original diagnosis right. Go and see your doctor and mention this conditions if you think it may be what is causing your leg numbness, the doctor can check to see if it’s the right diagnosis for you and arrange the proper treatment.