A Study Comparing the Effectiveness and Safety of Extended Release (ER) Tramadol Hydrochloride (HCl)/Acetaminophen With Immediate Release (IR) Tramadol HCl/Acetaminophen in Participants With Moderate to Severe Postoperative Pain

The purpose of this study is to compare the efficacy and safety of extended release (ER) tramadol hydrochloride (HCl)/acetaminophen with immediate release (IR) tramadol HCl/acetaminophen in participants with moderate to severe (very serious, life threatening) postoperative pain.

This study is a randomized (study drug assigned by chance), multicenter (when more than 1 hospital or medical school team work on a medical research study), active-controlled, parallel group (each group of participants will be treated at the same time), double-blind (neither physician nor participant knows the treatment that the participant receives) study. The duration of the treatment will be 2 days and will be conducted in 4 periods: screening period (from 33 to 2 days before study drug administration to the first surgical incision), surgical period (to 1 day before study drug administration), qualification period (1 day) and double-blind treatment period (1 to 2 days). Participants will be randomly assigned to 2 groups: study drug treatment group (ER) and comparator treatment group (IR). Participants will be administered 2 tablets of ER tramadol HCl (75 milligram \[mg\])/acetaminophen (650 mg) along with 2 tablets of placebo matching to IR tramadol HCl/acetaminophen in study drug treatment group; and 2 tablets of IR tramadol HCl (37.5 mg)/acetaminophen (325 mg) along with 2 tablets of placebo matching to ER tramadol HCl/acetaminophen in comparator treatment group respectively at 0, 12, 24 and 36 hours. Participants will also be administered 2 tablets of placebo matching to IR tramadol HCl/acetaminophen in study drug treatment group; and 2 tablets of IR tramadol HCl/acetaminophen in comparator treatment group respectively at 6, 18, 30 and 42 hours. Participants will be administered investigational product at 6-hour interval from the time of the first investigational product administration over 48 hours. Efficacy will be assessed using 11-point numeric rating scale (NRS). Participants' safety will be monitored throughout the study.

Eligibility Criteria:
Inclusion Criteria:

* Participants who are scheduled to have standard primary (non-revision) unilateral (having to do with only 1 side of a structure) total knee replacement arthroplasty (TKRA-surgery to fix a joint) for non-inflammatory (no swelling, redness, and pain in tissues caused by injury or damage) degenerative joint disease (NIDJD)
* Participants who are capable of oral (having to do with the mouth) intake
* Women must be: postmenopausal (for at least 1 year), surgically sterile, abstinent (not having sexual intercourse), or practicing a highly effective method of birth control before participation in the study and who agree to continue to use the same method of birth control throughout the study in cases of women of childbearing potential
* Male participants must practice contraception, and must agree not to donate his sperms for 1 month after the last dose of study drug
* Participants who will complain of baseline pain of intensity of greater than or equal to 4 on 11-point numeric rating scale (NRS) measured within 1 hour prior to randomization (study drug assigned by chance) and a maximum of 6 hours after discontinuation of participant controlled analgesia (PCA) after at least 12 hours of application following TKRA

Exclusion Criteria:

* Participants with Illness history (severe \[very serious, life threatening\] hepatic \[having to do with the liver\] failure, severe renal \[having to do with the kidney\] failure; severe respiratory depression; risk for mental fog with head injury or brain lesions \[abnormal area of tissue, such as a wound, sore, rash, or boil\]; digestive ulcer \[sore\], severe blood abnormalities; severe cardiac insufficiency; aspirin asthma \[asthmatic attack-breathing disorder in which there is a wheezing and difficulty in breathing; caused by non-steroidal anti-inflammatory drugs\] or history of aspirin asthma; history of epilepsy \[seizure disorder\]; rheumatism, significant psychiatric disorder or taking antipsychotic drugs for psychiatric treatment)
* Administration of disallowed therapy such as: administration of oral, patch, injection or local analgesics (drug used to control pain) acting centrally (the brain and the spinal cord) or peripherally (not central) before study drug administration after completion of PCA application, surgery is conducted simultaneously in addition to TKRA, administration of monoamine oxidase (MAO) inhibitors or discontinuation of the administration within 2 weeks, tricyclic antidepressants that may increase the seizure (sudden, uncontrolled muscle spasms and loss of consciousness resulting from abnormal brain function) risk when concomitantly (given at the same time) administered, neuroleptics, or drugs that may lower the seizure threshold, use of sedatives (a medication to calm or make less anxious) other than that used for general anesthesia (loss of sensation or feeling) during surgery
* Participants who used any study drug or investigational medical device within 30 days before the start of the treatment
* Participants requiring postoperative intensive care unit (ICU) care
* Participants having hypersensitivity to tramadol or acetaminophen