Objective:To analyze the different analgesic response to intraarticular morphine and bupivacaine in different types of arthroscopic surgery.Design:Prospective, randomized and double‐blinded. Fifty‐three consecutive patients undergoing an arthroscopic knee procedure under general anesthesia. They were studied separately in 2 groups (types of surgery): (1) “Low inflammatory surgery”: diagnostic arthroscopy, partial meniscectomy; and (2) “High inflammatory surgery”: ACL (anterior cruciate ligament) reconstruction, lateral release, patellar shaving and plicae removal. At the end of the procedure, patients were randomized to receive 25 mL of bupivacaine 0.25% with epinephrine (1/200,000), 5 mg of morphine, or saline (placebo) into the knee joint. Postoperative pain was determined through the visual analog scale (VAS). Supplemental analgesia (ketorolac) was administered via intravenous patient‐controlled analgesia (IV PCA). Pain and requirements of analgesia were compared between bupivacaine, morphine, and placebo in each group of surgery.Results:When considering only the “Low inflammatory” group of patients, those who received bupivacaine showed a lower postoperative pain score at 4 and 8 hours (P< 0.05). When considering only the “High inflammatory” group, the patients who received morphine showed a lower postoperative pain score at 24 hours and less requirements of ketorolac (P< 0.05).Conclusions:The analgesic effect of morphine and bupivacaine is different depending on the type of arthroscopic surgery. Intraarticular bupivacaine is effective in surgeries with a low inflammatory response. For surgeries with a higher inflammatory response, morphine has a better analgesic effect. Postoperative intraarticular analgesic therapy should be indicated according to the performed arthroscopic procedure.