A rare condition. It is easy to misdiagnosis as other condition, such as sciatica, hip arthritis, knee arthritis, greater trochanteric bursitis, etc.. Patients may be treated with epidural steroid injection, hip or knee joint injection, trochanteric bursa injection without help. some patients even has total hip placement or total knee replacement.
35 years old female was referred to me due to the right sided lower back pain, and lateral thigh pain and lateral knee pain for 3 year duration. The patient was diagnosed as disc herniation with radiculopathy, hip osteoarthritis, knee osteoarthritis and myralgia. She was treated with interventional pain management procedures, including lumbar epidural steroid injection, transforeminal epidural steroid injection, hip injection, Knee injection, trigger point injection, and greater trochanteric steroid injection without any relief of her pain. The patient had to take Oxycontin 80mg three times a day and Percocet 6 tablets a day. However, the pain was still severe and unbearable.
Examination in my office revealed severe pain on the right buttock, groin area, lateral thigh and knee. There is severe pain with any movement of hip and back, and decreased pin prick sendation on the lateral thigh in a oval shape.
There is L4/L5 disc herniation in her MRI of lumbar spine. The EMG test was within normal limits.
The patient did not respond to interventional pain management procedures mentioned above at all. The heavy dose of pain medications reduced pain somewhat, but the pain is still unbearable. When we have this condition, we should step back, looking for possiblities as below:
Atypical presentation of common condition
Multiple possible diagnosis
As showed in Fig 1, the patient had disc herniation between L4 and L5 vertibra. It compresses L5 nerve root. L5 nerve root compression will results in the leg pain from low back down to the leg and foot. However, this paitent only have pain on the lateral thigh. Obvisiouly, the disc herniation did not cause the pain the patient had.
This is rare condition and often misdiagnosed as sciatica pain or hip and knee arthritis. Some patients may have total hip replacement because of this condtion.
A nerve, lateral femoral cutaneous nerve, innervates on the outer portion of the lateral thigh. When this nerve is entrapped or pinched as it passed under ligment of groin, inguinal ligament (see Fig 3), it will cause the pain on the outer portion of lateral thigh and surrounding areas as what the patient had (see Fig 4).
Patients may have pain and abnormal sensations, such as burning, sharp pain, and numbness in the distribution of this nerve on the outer and part of the thigh and surrounding area.
The diagnosis for this patient should be Meralgia paresthetica. It is also called lateral femoral cutaneous nerve syndrome.
Causes of meralgia paresthetica
If you have meralgia paresthetica, a large sensory nerve in your outer thigh doesn’t have enough room to pass through your hip bone or joints. This may be due to swelling, trauma, or increased pressure in this area.
A lot of things can squeeze or damage the nerve, including:
Injury, such as trauma from a seatbelt during a car crash
A disease that can damage the nerves, like diabetes
Repetitive motions that could irritate the nerve, such as certain leg movements
Standing or walking for a long time
The treatment of meralgia paresthetica usually involves addressing the underlying cause.
Meralgia paresthetica can also be treated by local cortisone injection at the point where the nerve crosses the crease in the groin.
Infrequently, surgical release of the nerve is necessary.
Treatment for Meralgia Paresthetica
The goal of treatment is to relieve entrapment of the lateral cutaneous nerve. The treatment can be different depending on the cause.
Wearing loose clothes.
Taking anti-inflammatory pain medications, such as Ibuprofen, Aleve.
Steroid injection can be a choice if the conservative injection does not reduce the pain
Surgery can be another option to relieve the compression surrounding the nerve.
The patient we mentioned above was treated with steroid injections. The pain was much better after the first injection and the pain medications were tapered off. The pain was resolved after subsequent two more injection.
fig. 1 L4/L5 disc herniation compresses L5 nerve root.
Fig. L5 nerve root compression results in the leg pain from low back to foot.
fig. 1 Lateral femoral cutaneous nerve is formed fro L2 and L3 nerve root. It travels under inguinal ligament and then innervated on the lateral thigh.
fig. 1 If lateral femoral cutaneous nerve is trapped under inguinal ligament, there is pain on the lateral thigh.
fig. 1 Sketch drawing shows lateral femoral cutaneous nerve and its innervation.