Keywords: saphenous neuritis, gonalgia paresthetica, saphenous nerve, neuritis, Neuropathia patellae, treatment, physiotherapy, studies. Sources: PubMed, Web of Knowledge, Google, Medical Dictionary (Dutch).
“Gonalgia Paresthetica” is also known as Neuropatia patellae or more commonly known as saphenous neuritis, and is a chronic irritation of the Ramus Infrapattelaris (incl. the nervus saphenous). This pathology is caused by a compression or irritation of the saphenous nerve which develops pain in many cases on the anterior side of the knee or on the medial side of the knee.
Clinically Relevant Anatomy (image)
The saphenous nerve is the largest cutaneous branch of the femoral nerve. This nerve travels with the superficial femoral artery and vein, and passes through the adductor canal. From the adductor canal it continues toward the skin of the medial lower leg and foot. The floor of the saphenous nerve is composed of the musculus adductor longus and magnus, and this nerve borders anterolateral to the musculus vastus medialis. The saphenous nerve innervates the musculus sartorius and the musculus vastus medialis.
Saphenous neuritis occurs mainly to adults after a physical activity or after other strenuous activities such as a walk or after a long day at work. The pain is especially felt in response to limb movements that cause nerve stretch. Pain characterized by saphenous neuritis is mostly activity-related pain, but it can also be characterized as rest-pain. Clinical research shows elective pressure pain in the canal of Hunter (Adductor Canal) at the height of the medial thigh. It can also find diffuse tenderness at the medial structures and at the pes anserinus. This pathology can appear beside other common problems, such as osteoarthritis or patellofemoral pain syndrome. The clinical appearance of saphenous neuritis is characterized by allodynia along the nerve. Many studies concluded that it is very important to know the anatomy of this nerve to evaluate and treat saphenous neuritis correctly. There are different causes of saphenous neuritis. The most frequent cause is the compression of the nerve, along its anatomic course, the Adductor Canal. The pain is most sensible at the joint line associated with hyperaesthesia or hypoaesthesia on the medial side of the lower leg (knee) when it’s caused by compression. Secondly it is the traumatic cause to saphenous neuritis. Table 1 illustrates a few causes which may produce saphenous neuritis, on a direct and indirect manner.
DIRECT Trauma (for example: rotation injury) Direct contact: compression (for example: Dashboard injury) Cut-incision Scar-synovial Resection Stretch PLRI (Posterolateral Rotator Instability)
INDIRECT Reflex Sympathetic dystrophy Fibromyalgia Lumbar Dise Disease Degenerative joint disease of the knee Meniscal tear Surgery
Medial pain at the knee is often a primary indication of saphenous neuritis. But sometimes the pain develops a few days after the initial injury. The pain of saphenous neuritis only appears with exercise or play activity. It can be devastating, but may also come and go. The pain can be characterized by sharp pain or constant pain. When the patient got pain on the anterior or/and medial side of the knee, especially on the joint line during palpation 7.3 cm proximal and 9.8 cm medial to the superior pole of the patella, it is an important indication of saphenous neuritis. For a physiotherapist, the most efficient hallmark of saphenous neuritis is tenderness to light palpation along the nervus saphenous’ course. The tenderness may mainly apparent at the nerve’s exit from the adductor canal, near the medial joint line or along the nerve in the proximal third of the leg. Starting from the adductor canal, it is possible to elicit the exact course of the irritated saphenous nerve. In some cases, an electromyography (EMG), which tests the activity of the muscles and the sensory guidance, can show a delayed conduction of the saphenous nerve. This feature is mostly related to neuritis of this nerve.
It is important for a physiotherapist to recognize saphenous neuritis immediately during the diagnosis of a knee-injury. Otherwise it can confuse the patient’s clinical picture, complicate treatment and compromise results. It should be part of every routine while examining the knee.
When saphenous neuritis is diagnostically confirmed with palpation, the best option consists is nonsurgical care. This may include activity modification and/or oral analgesics (including narcotics and nonsteroidal anti-inflammatory medication, protective padding, topical analgesic cream, etc.). Symptoms of saphenous neuritis may subside with time. If it is not the case, injection of local anesthetic, without corticosteroid, can be initiated. When this does not solve the neuritis, surgical intervention is recommended by decompression, or neuroma excision may follow.
DUDLEY M.D., FERRARI A., 2008. Reflections and Conclusions about the Problem Knee. Mill City Press. (level of evidence 5) MORGANTI C.M., MCFARLAND E.G., COSGAREA A.J, 2002. saphenous Neuritis: A poorly understoor cause of medial knee pain. Journal of the American Academy of Orthopaedic Surgeons (JAAOS). (level of evidence 2C) MARTINELLI P., MONTAGNA P., COCCAGNA G, 1982. Neuropathy of the infrapatellar branch of the saphenous nerve in the differential diagnosis of knee pain. The Italian Journal of Neurological Sciences. (level of evidence 1B) TENNENT T.D., BIRCH N.C., HOLMES M.J., BIRCH R., GODDARD N.J., 1998. Knee pain and the infrapatellar branch of the saphenous nerve. Journal of the Royal Society of Medicine. (Level of evidence 3B) HULSE R, WYNICK D, DONALDSON L.F., 2009. Intact cutaneous C fibre afferent properties in mechanical and cold neuropathic allodynia. Elsevier. (level of evidence 3B)