Infrapatellar Saphenous Neuralgia – Diagnosis and Treatment

Persistent anterior knee pain, especially after surgery, can be very frustrating forthe patient and the clinician. Injury to the infrapatellar branch of the saphenousnerve (IPS) is not uncommon after knee surgeries and trauma, yet the diagnosisand treatment of IPS neuralgia is not usually taught in pain training programs. Inthis case report, we describe the anatomy of the saphenous nerve and specificallythe infrapatellar saphenous nerve branch; we also discuss the types of surgicaltrauma, the clinical presentation, the diagnostic modalities, the diagnosticinjection technique, and the treatment options. As early as 1945, surgeons werecautioned regarding the potential surgical trauma to the IPS. Although manyauthors dismissed the nerve damage as unavoidable, the IPS is now recognized asa potential cause of persistent anterior and anteriomedial knee pain. Even moreconcerning, damage to peripheral nerves such as the IPS has been identified as thecause and potential perpetuating factor for conditions such as complex regionalpain syndromes (CRPS). Because the clinical presentation may be vague, it hasoften been misdiagnosed and underdiagnosed. There is a documented vasomotorinstability, but, unfortunately, sympathetic blocks will not address the underlyingpathology, and therefore patients often will not respond to this modality, althoughthe correct diagnosis can lead to rapid and gratifying resolution of the pathology.An entity unknown to the clinician is never diagnosed, and so it is important tofamiliarize pain physicians with IPS neuropathy so that they may be able to offerassistance when this painful condition arises.Key words: infrapatellar saphenous nerve, saphenous neuralgia, nerve injury,knee pain, postoperative pain, peripheral nerve entrapment, diagnostic nerveblocks, complex regional pain syndrome, cryoneuroablation