Saphenous Neuralgia: Identifying Key Clinical Features

PURPOSE: The purpose of this study was to describe clinical findings that aid in the diagnosis of saphenous neuralgia, thereby addressing the challenge of its frequent misidentification in patients with knee pain. METHODS: A cohort study was conducted on 42 patients (49 knees) with knee pain who underwent a diagnostic nerve block at Hunter’s Canal with 5-8 mL of 1% lidocaine (criteria: >80% improvement in pain) for suspected saphenous neuralgia. Descriptive analyses of responders were conducted and sensitivity and specificity in comparison to non-responders were calculated for key findings. RESULTS: 31 patients (35 knees) had a positive response. Female sex predominated with a 5:1 ratio compared to males. Patient age was relatively evenly distributed (Mean +/- SD = 41.8 +/- 20.8) across a broad age span (Range = 14 - 90 years). BMI (27.4 +/- 6.9; 15.4 - 41.8 kg/m2) primarily included normal (N = 9), overweight (N = 6), and obese class I (N = 11) patients. The duration of pain was relatively evenly distributed among short (0-6 months, N = 14), moderate (3-24 months, N = 13), and long (24+ months, N = 8) durations. Common prior diagnoses included patellofemoral pain syndrome (54%), osteoarthritis (20%), and medial meniscus tears (17%). 65% had an insidious onset of pain, and a fall (19%) was the most common acute event associated with onset of pain. Patients described pain including the medial (63%), anterior (57%), and/or lateral (20%) knee. Sensitivity and specificity were determined for neuropathic symptoms (34%; 79%), distal medial leg symptoms (31%; 100%), and the Hunter's Canal Compression Test (80%; 100%). CONCLUSIONS: Saphenous neuralgia should be considered in patients who have anterior and/or medial knee pain, particularly for those unresponsive to standard treatment for common knee pathology and female patients. Saphenous neuralgia should be considered across a broad age and pain duration spectrum, and the presence of lateral pain does not obviate this as a potential diagnosis. Historical items commonly associated with peripheral compression neuropathies (neuropathic symptoms) and with the anatomy of the saphenous nerve (distal medial leg symptoms) lack sensitivity, whereas the Hunter’s Canal Compression Test may significantly aid diagnosis due to its relatively good sensitivity and excellent specificity.