Sometimes you may have felt a strange tingling or burning pain on the inside of your leg, especially in the area below the knee. Sometimes it may feel worse when you walk or bend your leg. We often think that this is a pinched vein or a torn muscle. Yes, there is some truth to that story. Today we are going to talk about a very important nerve in our leg, but many people do not know its name. That is the saphenous nerve. Even a small damage to this nerve can cause such discomfort.
Okay, so what is this saphenous nerve?
Simply put, the saphenous nerve is a sensory nerve that runs down the inside of your leg. Now you might be wondering what a sensory nerve is. Think of our body as a complex electrical circuit. The wires in this circuit are called nerves. There are two types of these wires.
1. Motor Nerves: These carry messages from the brain to the muscles. These nerves give commands like "shake your arm" and "lift your leg."
2. Sensory Nerves: These do the opposite. They carry information about what we feel in our skin and muscles (heat, cold, pain, touch) back to the brain.
The saphenous nerve belongs to the second type, the sensory nerve. This means that it does not command the muscles to move, but it is the one that reports everything that is felt on the inside of your leg to the brain. This is part of our body's peripheral nervous system . That is, it is part of the network of nerves that extends throughout the body, outside the central system, which is the brain and spinal cord.
What is the benefit of this nerve to our body?
The main function of the saphenous nerve is to transmit sensations from the inside of your leg to the brain and spinal cord. It's like a telephone line from the skin of your leg to your brain. What kind of information goes through this line?
| Sensation type | Simply put... |
|---|---|
| Leg Position | Even if you close your eyes, you can still feel where your leg is, whether it's bent or extended. That's how this nerve helps to give the brain information about the position of your leg. |
| Pain | If something hits the inside of the leg, if there's a scratch, if there's a thorn in it, this nerve sends a signal to the brain saying, "It hurts here." |
| Temperature | If you drop some hot water on your leg, or if you rub an ice cube on it, you feel the heat or cold because of this nerve. |
| Touch | When someone touches the inside of your leg, when you rub your clothes, or when a mosquito bites you, you feel that touch because of the activity of this nerve. |
Where exactly in the leg does this sensation come from?
You have one saphenous nerve in each of your legs. This nerve mainly provides sensation to the inside of your leg. That means:
- Below the knee to the inner side
- To the inside of the chest
- To the inside of the ankle
- The arch of your foot
Simply put, this nerve helps provide sensation on the inside of your leg, from the knee all the way to the sole of your foot.
How is this nerve important to us medically?
In addition to telling the brain what we feel, this nerve is also very useful to doctors. That is for a treatment called nerve block .
A nerve block involves selecting a specific nerve and injecting it with an injection to temporarily stop the nerve from functioning. It's like blowing out a fuse. This stops the pain signals from that nerve to the brain, and the area that receives sensation from that nerve becomes numb.
Doctors perform a nerve block on the saphenous nerve for three main reasons:
1. Stop the pain in case of an accident: Imagine that you have suffered a severe injury to the inside of your leg. At that time, numbing this nerve to temporarily control the pain can provide great relief.
2. To numb the area before surgery: Instead of completely losing consciousness before a minor surgery on the inside of the leg, ankle, or sole, you can numb just this nerve before the surgery.
3. As a treatment for persistent pain: Sometimes there can be chronic pain associated with this nerve. In such cases, this method is also used to control pain.
How is this nerve located in our leg?
Although this is a bit technical, let's understand it simply.
The saphenous nerve starts at the top of your thigh, on the inside, in an area called the femoral triangle . This is like a major junction. Several important blood vessels and nerves to the leg pass through this area.
- The saphenous nerve, which begins at this junction, travels down through the muscles on the inner side of the thigh, through a tunnel-like passage called the adductor canal .
- As it emerges from this tunnel, near the knee, the nerve divides into two main branches.
- One branch (the `infrapatellar branch`) provides sensation to the skin below the kneecap.
- The other main branch (the `sartorial branch`) goes down past the knee and gives off smaller branches to provide sensation to the groin, ankle, and inner side of the foot.
This nerve is not located on the surface of the skin of the leg, but rather a little deeper. Therefore, it is rarely damaged by a minor bruise or scrape.
What conditions affect the saphenous nerve?
As we mentioned earlier, this nerve is well protected inside the leg, so it is less likely to be injured. However, in some cases, this nerve can be damaged or compressed.
The two main reasons are:
- Entrapment / Pinched Nerve: Abnormal pressure on a nerve from surrounding muscles, ligaments, or other tissues.
- Trauma: Deep cuts or wounds to the inside of the leg.
However, more than these two reasons, the most common and main reason for damage to the saphenous nerve is damage that occurs as a complication of certain surgeries . Because during surgeries performed along the path of this nerve, there is a possibility of unintentional damage to the nerve.
| Type of surgery that can cause damage | Simply put, that means... |
|---|---|
| ACL Reconstruction | A surgery performed when an important ligament that helps stabilize the knee joint is torn. |
| Knee Arthroscopy | A surgery in which a thin instrument with a camera is inserted into the knee to examine and treat the inside. |
| Meniscus Cartilage Surgery (Meniscus Repair) | Surgery to repair a torn cartilage inside the knee joint. |
| Ankle Surgery | Surgeries for ankle fractures, severe arthritis conditions, etc. |
| Varicose Vein Stripping | Surgical removal of varicose veins, which are visible on the surface of the legs. |
| Bypass surgery (CABG Surgery) | When a blood vessel in the heart is blocked, a surgery to restore blood flow by grafting a vein from the leg (saphenous vein). This can damage the saphenous nerve, which runs right next to the saphenous vein. |
| Cardiac Catheterization | Tests and treatments are performed by passing a thin tube into the heart through an incision made in the groin area. |
What symptoms should I see a doctor for?
If you continue to experience one or more of the following symptoms on the inside of your leg, especially around the knee, shin, or ankle, it is important to see a doctor to discuss it.
- Tingling and Numbness
- Burning sensation
- Shooting pain
- Dull, Achy Pain
- Muscle tightness in that area
When you tell your doctor about these symptoms, he or she will examine you. If necessary, they may refer you to a neurologist. Sometimes, they may recommend a special test, such as an EMG (Electromyography), to determine the exact function of the nerve.
The most important thing is, don't ignore any of these symptoms, thinking, "It just happened." It's especially important to let your doctor know about these symptoms, especially if you've recently had knee, ankle, or heart surgery.
If you are scheduled to have surgery, it is your right to talk to your doctor beforehand about these potential complications. Having an experienced doctor perform the surgery can greatly reduce these risks.
Take-Home Message
- The saphenous nerve is an important nerve that carries sensations like touch, pain, and temperature from the inside of your leg (from the knee to the sole of your foot) to the brain.
- Damage to this nerve is generally rare, but it most often occurs as a complication of surgeries such as knee, ankle, or bypass surgery.
- If you have persistent tingling, burning, or sharp pain on the inside of your leg, it could be a problem with the saphenous nerve.
- If you have any of these symptoms, do not ignore them and see your doctor immediately for advice.
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