Pain below the kneecap can be caused by many things, such as patellofemoral pain, knee arthritis, and tendonitis. A less common cause of knee pain is saphenous entrapment close to the knee, which can cause significant knee discomfort and reduced mobility. What causes saphenous nerve pain, and how can it be treated?  

What is the Saphenous Nerve?

The saphenous nerve is a branch arising from the femoral nerve in the front of the thigh. It starts above the inside of the knee and courses down to the inner part of the shin and foot. It provides sensation to the inner side of the knee, leg, and foot.

saphenous nerve anatomy lower leg

Causes of Saphenous Nerve Entrapment  

There are many potential causes of saphenous nerve entrapment, including the following:

  • Trauma or Injury: Direct trauma to the knee, thigh, or shin, such as from sports injuries or accidents, can bruise the nerve. Ankle sprains or prolonged kneeling can also stretch or irritate the nerve.
  • Surgical Procedures: Surgeries can inadvertently damage the saphenous nerve. Knee arthroscopy, total knee replacement, and vein harvesting for coronary artery bypass grafting are examples of surgeries that can lead to saphenous nerve pain.
  • Compression or Entrapment: Scar tissue or adhesions at specific sites, such as the adductor canal of the lower thigh (Hunter’s canal), can cause nerve entrapment.
  • Inflammation: Inflammatory conditions, such as knee arthritis or tendinitis, may indirectly irritate the nerves.
  • Neuritis: Conditions like diabetes or peripheral neuropathy can increase susceptibility to nerve pain.

Saphenous Nerve Pain Symptoms

In general, saphenous nerve pain manifests with sensory changes, which may include a few of the following:

  • Patients describe pain as burning, sharp, or aching along the inner thigh, knee, or shin. It is often exacerbated by movements such as bending the knee, walking, or kneeling.
  • Pins-and-needles sensation or numbness is common on the inside of the knee, shin, or foot.
  • Sometimes, there is increased sensitivity to light touch or pressure.

Saphenous nerve pain location 

Patients often point to the inner aspect of the knee just below the kneecap. Sometimes, the pain moves to the inner shin or foot.

anteromedial knee pain in women secondary to saphenous nerve pain

How to Diagnose Saphenous Nerve Entrapment  

Saphenous nerve entrapment is often challenging to differentiate from other causes of inner knee pain, such as knee arthritis, pes bursitis, or patellar tendonitis.

Your doctor will take a comprehensive history, including a history of trauma or recent surgery. Examination of the saphenous nerve reveals focal tenderness over the inner thigh, knee, or shin. Tapping the nerve (also called percussion tenderness) reproduces the pain sensation.

Investigations help confirm nerve entrapment and exclude other causes of pain. Your doctor may consider the following investigations:

  • Ultrasound can visualise the nerve and identify compression, swelling, or injury. It can also identify possible causes of nerve trapping, such as arthritis, tendinitis, and scar tissue.
  • MRI helps rule out other soft-tissue and joint causes of knee or shin pain.
  • Nerve studies can confirm a saphenous nerve injury or other causes of nerve pain (such as peripheral neuritis).

Sometimes, we use a local anaesthetic nerve block with ultrasound guidance. A positive block helps confirm the diagnosis of a trapped nerve. 

Saphenous Nerve Pain Treatment 

If saphenous neuritis is suspected, we often use simple treatments first. Most patients respond to simple treatments within weeks to a few months. Modifying provocative activities, such as repeated kneeling with help, can be very effective. Physiotherapy incorporating specific nerve stretches and fascia release to reduce nerve tension can be very effective. A trial of topical medication, such as capsaicin cream or lidocaine patches, may help desensitise the nerve.

Medication 

Sometimes, we use specific medications to reduce nerve pain. Examples include amitriptyline and duloxetine. These medications have side effects, so you should ask your doctor whether you would be a good candidate for a medication trial.

Injections 

In general, we use injections when simple treatments are ineffective. Some physicians administer a localised corticosteroid injection to reduce swelling at the site of nerve entrapment. Sometimes, we use a more advanced procedure called a nerve hydrodissection. This procedure is a minimally invasive technique where fluid (saline, dextrose, or anaesthetic) is injected around the saphenous nerve under ultrasound guidance to release adhesions, reduce compression, and restore nerve mobility. Recently, platelet-rich plasma (PRP) has shown some success.

If injections are effective but the pain recurs, a more aggressive nerve ablation procedure may provide longer-term relief.

Surgery

We consider surgery in rare cases when conservative and minimally invasive treatments have failed. Procedures include:

  • Nerve Decompression: Releasing the nerve from surrounding tissues.
  • Neurolysis: Removal of scar tissue or adhesions compressing the nerve.

Generally, we should use surgery cautiously, only when the diagnosis is confirmed, and other treatments have failed.

Other Frequently Asked Questions about Saphenous Nerve Entrapment

Should injections for saphenous neuritis be performed using ultrasound?

Yes, Ultrasound-guided injections are more accurate and effective than landmark-guided injections.

Final Word from Sportdoctorlondon about Saphenous Nerve Pain

Saphenous nerve pain, although uncommon, can significantly impair quality of life. Early recognition of symptoms and accurate diagnosis are essential for effective management. Treatment options, ranging from physiotherapy and topical and oral medications to advanced interventions such as nerve hydrodissection, provide relief for most patients. You should see an experienced sports doctor who can diagnose and treat this condition.

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