The purpose of this study is to evaluate the efficacy and safety of Transdermal Therapeutic System (TTS)-fentanyl patch (transdermal patch containing a drug that is put on the skin so the drug will enter the body through the skin) in participants with moderate (medium level of seriousness) to severe (very serious, life threatening) pain of osteoarthritis (disorder, which is seen mostly in older persons, in which the joints become painful and stiff).

This is an open-label (a medical research study in which participants and researchers are told which treatments the participants are receiving, "unblinded"), single-arm, prospective (study following participants forward in time), study of TTS-fentanyl in participants with moderate to severe pain of osteoarthritis. The study will consist of 2 phases: screening phase up to 7 days before starting the treatment and treatment phase of 30 days. The first patch will be applied by investigator then by participants until 30 days. The dose of TTS-fentanyl can be increased, if needed, by 12.5 microgram per hour until adequate (reasonably good) pain control is achieved and taking into account the daily dose of supplemental paracetamol required by the participant. Other concomitant (given at the same time) analgesics (drug used to control pain) will not be used during this phase. Efficacy with regard to pain control will be recorded principally by the participant through questionnaires in a daily diary. This record will be used to support more detailed assessments at study visits on Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire. Participants' safety will be monitored.

Inclusion Criteria:

• Chronic (lasting a long time) primary osteoarthritis pain for more than 3 months with Visual Analog Scale (VAS) greater than or equal to 5
• Participants having moderate to severe pain (VAS greater than or equal to 5), which was not adequately controlled by weak opioids such as tramadol or codeine at optimal doses (at least 150 milligram [mg] per day for tramadol or 200 mg per day for codeine) for at least 7 consecutive days
• Participants who failed from other treatments such as operation or lack of efficacy of current treatment

Exclusion Criteria:

• Skin disease that prevents the use of the transdermal system or which could affect the absorption of fentanyl or local tolerability
• History or suspicion of alcohol or drug abuse within the past 5 years
• History of cardiac, nervous system or respiratory disease which in the investigator's judgment precludes participation in the study because of the potential for respiratory depression
• Confusion, reduced level of consciousness, or concomitant (given at the same time) psychiatric disorder which, in the opinion of the investigator, could prevent participation in the trial
• Pregnant or breast-feeding female; female participants of child bearing potential without adequate contraception

Baseline up to Day 30