[Analgesic effect of low-dose intra-articular morphine after ambulatory knee arthroscopy]

The purpose of this study was to demonstrate the effect of intra-articular morphine following knee arthroscopy performed in infiltration analgesia. Fifty-two healthy patients were randomized to receive either morphine 1 mg or placebo. The pain was assessed two, five, eight and 24 hours after the procedure by 1) a VAS scale and 2) the amount of acetaminophen consumed. Demographic data in the two groups were similar. The pain scores at eight and 24 hours and the acetaminophen consumption after eight hours were lower in the morphine group (p < 0.05). Our results confirm the hypothesis of peripherally distributed opioid receptors. Stratifying data in therapeutic vs. diagnostic arthroscopy suggests an additional effect of morphine in patients undergoing therapy (0.05 < p < 0.10), an aspect which supports the hypothesis of peripherally administered morphine acting as a potential suppressor of the substance P mediated cytokine cascade. Intraarticular morphine 1 mg after knee arthroscopy offers efficient analgesia lasting more than 24 hours. The method is devoid of side effects and deserves wider recognition.