Disclosures: Mohamed H. Shitia, DO: No financial relationships or conflicts of interest

Case Diagnosis: 51-year-old female with a history of right upper extremity complex regional pain syndrome (CRPS) type I presenting with an 8-month history of left medial knee/distal thigh pain.

Case Description or Program Description: This patient was referred to the outpatient musculoskeletal clinic by her primary care provider for persistent left thigh pain following an injury eight months prior. She had struck a metal doorframe with her distal medial thigh, and afterwards developed a deep, burning pain at the site of trauma. There was associated numbness, dysesthesias, allodynia, heat/cold intolerance, color changes, and swelling. Examination revealed positive Tinel’s over the adductor canal and allodynia along the medial distal thigh. Knee radiographs demonstrated mild medial compartment osteoarthritis. EMG displayed evidence of isolated saphenous neuropathy.

Setting: Outpatient musculoskeletal clinic.

Assessment/Results: The patient was offered ultrasonographic evaluation of the medial thigh with possible ultrasound-guided saphenous nerve block which she declined. She preferred a more conservative approach involving topical capsaicin cream. At 3-month follow-up, she noted gradual improvement in symptoms but still had intermittent discoloration and swelling of the medial thigh.

Discussion (relevance): Saphenous neuritis is a rare cause of anteromedial knee pain that is often overlooked for more common pathologies such as osteoarthritis, patellofemoral syndrome, meniscal injury, and lumbar radiculopathy. It can be caused by compression or trauma, and has been implicated in post-arthroplasty pain. In this patient, a diagnosis of CRPS type II is also considered, especially given her history of upper limb CRPS. Diagnosis of saphenous neuritis can be confirmed via EMG, MRI, ultrasonography, or diagnostic block. Most cases resolve with non-surgical treatment, but refractory cases may require surgical decompression.

Conclusions: Isolated saphenous neuritis is an uncommon cause of post-traumatic medial knee pain. Clinicians should consider this diagnosis in patients who exhibit allodynia or dysesthesias, particularly in the setting of direct trauma or compression to the distal anteromedial thigh, or in refractory cases.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/saphenous-neuritis-in-a-patient-with-complex-regional-pain-syndrome-a-case-report/