 This is an open-label all people know the identity of the intervention, randomized study drug assigned by chance, controlled study to evaluate the efficacy, safety and effects on QOL of tramadolAPAP as an add-on therapy in Filipino participants suffering from chronic pain because of chronic osteoarthritis. Participants will be randomly assigned to 2 groups: tramadolAPAP group and non tramadolAPAP group. Participants in tramadolAPAP group will receive celecoxib 200 milligram mg and fixed dose combination of tramadol 37.5 mgAPAP 325 mg as add on therapy, while the participants in non-tramadolAPAP group will receive celecoxib 200 mg only. The total duration of the study will be 4 weeks. The participants in both the groups will be given celecoxib 200 mg once daily for 4 weeks. In addition, the participants in the tramadolAPAP group will be given add-on tramadolAPAP doses 3 times a day for 4 weeks. Participants will be asked to return for follow-up at Weeks 2 and 4. Efficacy will be assessed using 100 millimeter mm Visual Analog Scale VAS while QOL will be assessed using the Oswestry Disability Index ODI. Participant safety will be monitored throughout the study. 