Randomized, double blinded comparative trial of intradermal injections of lignocaine versus N-saline around the knee to relieve pain in patients awaiting total knee replacement

Objectives: We report a randomized, double-blinded comparative study assessing the efficacy of local anesthetic with N-saline intradermal blocks around the knee to reduce pain and improve patient satisfaction while waiting for a total knee joint replacement. Methods: Patients were offered involvement in this study while on the hospital waiting list for a knee replacement. Eligible patients, after completing a prestudy assessment, received an average of 6.3 (range: 1 to 10) intradermal injections of 0.5mL either saline or 1% lignocaine injections into tender points around the knee. Patients were assessed at 2 hours and 1 week after the injections. Pain was assessed using 0 to 100 visual analog pain scale. Global perceived effect (satisfaction) was measured on a 7-point Likert scale. Results: Thirty-two of 34 patients attended at 1-week assessment, 24 (75%) felt that they were improved, and 8 (25%) considered they were unchanged or worse. In both the saline and lignocaine groups, 12 of 16 patients felt that they had improved. N-saline proved as effective as lignocaine in reducing knee pain when injected intradermally. Seventy-five percent of patients were improved at 1 week.