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Roots of Post-Surgical Knee Nerve Damage Uncovered

For the first time using ultrasound imaging, researchers have identified microscopic nerves.

A PPM Brief

Two recent studies1,2 have uncovered tiny cutaneous nerves on the anterior and medial thigh and around the knee using high-resolution ultrasound imaging, which may explain the occurrence of chronic pain following knee operations. Previously, it has been deemed impossible to demonstrate that these tiny cutaneous nerves (less than 1-mm thick) exist around the knees.

In the first study,1 a team of researchers at the Medical University of Vienna, Austria located the entire course of ramus infrapatellaris (a sensitive nerve branch in front of and below the kneecap) with high-resolution ultrasound imaging. They showed that neuropathy of the intermediate and medial femoral cutaneous nerve can be reliably visualized throughout the course of the nerves, both in anatomical specimens and in patients.

Nerve damage shown to be cause of unexplained chronic pain following knee operationsPatients frequently experience severe chronic pain following knee operations. (Source: 123RF)

The second study,2 also led by researchers at the Medical University of Vienna, Austria, highlighted the branched anterior cutaneous branches of the femoral nerve, nervus femoralis, confirming the reliability to visualize these branches using high-resolution ultrasound in anatomic specimens and in healthy volunteers, which could enhance the diagnostic and therapeutic management of patients with anteromedial knee pain. It was also found that the nerve pathways are highly variable for each patient.

To accurately isolate the nerve branches causing the pain, it is essential to carry out a "diagnostic blockade," according to lead researcher Georg Riegler, MD, lead researcher from MedUni Vienna's Department of Biomedical Imaging and Image-guided Therapy. "Since the nerve supply is so variable, it is essential to first make sure which of these tiny nerves [are] causing the pain,” he said in a press release.3 “This can only be done by selectively temporarily anesthetizing, or blockading, the suspected nerve, with a maximum of 1 mL of anesthetic. If the pain is significantly reduced immediately after a blockade has been done and returns once the anesthetic has worn off, then we have located the problem."

One of the first options for treating nerve pain in the knee is to use localized pain patches or physiotherapy, followed by ultrasound-guided treatment. Other possibilities include cortisone injections, radiofrequency ablation, and surgical procedures. Dr. Riegler urged the importance of determining the exact position of the damaged nerve fibers before giving any targeted treatment to combat nerve pain.

Last updated on: October 26, 2018
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