A femoral nerve block is a targeted, image-guided injection that places anesthetic around the femoral nerve to help diagnose and relieve pain across the front of the thigh and the knee.
OVERVIEW
What a femoral nerve block is and how it works
The femoral nerve is one of the largest nerves in the leg. It arises from the lower lumbar spine, travels through the pelvis, and passes under the inguinal ligament into the groin, where it supplies sensation to the front of the thigh and (through its saphenous branch) the inner lower leg, and powers the quadriceps muscles that straighten the knee. When this nerve is irritated, compressed, or is the source of injury-related or post-surgical pain, a femoral nerve block can interrupt those pain signals.
During the procedure, a physician at Columbia Pain & Spine Institute places a small amount of local anesthetic — sometimes combined with a corticosteroid — around the femoral nerve in the groin region. The anesthetic temporarily blocks the nerve from transmitting pain signals to the brain. A femoral nerve block can serve two purposes: it can be diagnostic, helping confirm that the femoral nerve is the source of a patient’s anterior thigh or knee pain, and it can be therapeutic, providing a window of relief that supports physical therapy and rehabilitation.
CONDITIONS
What a femoral nerve block commonly treats
A femoral nerve block may be considered for pain felt in the anterior (front) thigh and knee that involves the femoral nerve, and to help identify that nerve as the pain source when the cause is unclear.
Commonly treats
Your physician will determine whether this block fits your diagnosis, or whether a related procedure such as a genicular nerve block for chronic knee pain or a sciatic nerve block for pain along the back of the leg is more appropriate. You can also see the full range of nerve block procedures we offer.
YOUR VISIT
What to expect
Before
Your physician reviews your history, exam findings, and imaging to confirm a femoral nerve block is appropriate. Let the office know about blood thinners, allergies, or possible pregnancy. The skin in the groin area is cleaned, and a local anesthetic numbs the injection site.
During
You lie on your back. Using ultrasound guidance — which lets the physician see the nerve and the nearby femoral artery and vein in real time — a thin needle is advanced toward the femoral nerve, and medication is delivered around it. The injection itself usually takes only a few minutes, and the full visit is generally brief.
After
You may notice numbness and temporary weakness in the thigh, which can make the knee feel like it may buckle. Because of this, you will need someone to drive you home, and you should avoid putting full weight on the leg until sensation and strength return. Many people resume normal activity the next day. Any steroid component may take several days to reach its full effect.
Femoral nerve blocks are performed in our procedure setting serving Gresham, Portland, and the greater Portland metro area. When a procedure calls for a surgery-center setting, care can be provided at the on-site Burnside Surgery Center in Gresham.
QUESTIONS
Frequently asked questions
Is a femoral nerve block diagnostic or therapeutic?
It can be both. A primarily diagnostic block uses local anesthetic to confirm whether the femoral nerve is causing your anterior thigh or knee pain. When a corticosteroid is added, the goal also becomes therapeutic — reducing inflammation around the nerve to provide longer-lasting relief. Your physician will explain which applies to your situation.
How long does the relief last?
The local anesthetic portion wears off within hours, which is expected. If a steroid is included, relief can build over a few days and may last weeks to months, though responses vary from person to person. There are no guaranteed outcomes, and your physician will discuss realistic expectations with you.
Will my leg feel weak afterward?
Temporary weakness in the quadriceps and a sense that the knee may give way are common right after the block, because the femoral nerve also controls the muscles that straighten the knee. This effect is short-lived as the anesthetic wears off, but it is why you should arrange a ride home and avoid bearing full weight on the leg until full strength returns.
LEARN MORE
Related care at Columbia Pain & Spine Institute
Nerve blocks
Explore our full range of diagnostic and therapeutic nerve block procedures.
Genicular nerve block
A targeted option for chronic knee pain — learn about the genicular nerve block.
Sciatic nerve block
For pain along the back of the leg, see the sciatic nerve block.
Browse all of our interventional pain services, or contact our Gresham and Portland team to learn whether a femoral nerve block is right for you. Referrals are accepted by fax, and questions are welcome by phone.
Contact Columbia Pain & Spine Institute