Background: Total knee arthroplasty represents one of the most painful surgeries. The aim of the study was to compare analgesia and adverse effects of intrathecal (IT) ketorolac versus IT morphine, versus the combination of IT ketorolac and morphine. Materials and Methods: After ethical approval and patient consent, 80 patients undergoing knee arthroplasty were randomized to one of 4 groups. All groups received 15 mg IT bupivacaine plus IT test drug (2 ml). The control group (CG) received saline as IT test drug. The morphine group (MG) received IT 200 g morphine, the ketorolac group (KG) IT 2 mg ketorolac and the morphine-ketorolac group (MKG) 200 g morphine + 2 mg ketorolac as test drugs. Pain and adverse effects were evaluated. P < 0.05 was considered significant. Results: The MG and KG were similar in their times to time to first rescue analgesic (440 ± 38 min and 381 ± 44 min, respectively). Both groups were longer when compared to the CG (170 ± 13 min) (P < 0.01). The MG and KG had lesser ketoprofen consumption compared to the CG (P < 0.05). The time to first rescue analgesic was longer to the MKG (926 ± 222 min) (15 h) compared to CG (P < 0.001) and to the MG and the KG (P < 0.01). MKG displayed lesser ketoprofen consumption compared to MG and KG (P < 0.05) and to the CG (P < 0.02). Conclusions: The data suggest a role for spinal ketorolac and morphine in orthopaedic surgery because this combination of agents provided 15 h of analgesia compared to 7 h after each drug alone, with no significant side-effects.