Jensen 1994.

Methods	Parallel, multicenter double‐blind RCT
Participants	Participants with radiologically confirmed diagnosis of OA of hip or knee Number of participants: tramadol group: 135; control group: 129 % women: active group: 76%; control group: 82%
Interventions	3–7‐day washout period: participants received up to 4 mg of acetaminophen. 2‐week double‐blind phase: participants with moderate to severe pain despite the acetaminophen were randomly allocated to: Active group 1: tramadol 100 mg 3 times/day Active group 2: dextropropoxyphene 100 mg 3 times/day Drugs were administered in capsules identical in appearance.
Outcomes	Assessment of pain/pain relief: pain during walking/daily activities, and pain during sleep (4‐point Likert scale) Assessment of functional impairment: climbing stairs, getting out of bed, or rising from a chair (4‐point Likert scale) Overall assessment of therapy at the last visit Adverse effects: signs and symptoms Withdrawals due to adverse events Extracted pain outcome: pain relief on VAS (0–100 mm) at 2 weeks, with lower values indicating benefit Extracted disability outcome: participant overall assessment (proxy for physical function)
Notes	Funded by Grünenthal GmBH, Aachen, Germany
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Patients were given a patient number in the order that they were enrolled, and received their allocated treatment according to a computer‐generated assignment schedule." (p.213)
Allocation concealment (selection bias)	Unclear risk	No mention of allocation concealment
Blinding of personnel	Unclear risk	Authors did not explicitly report blinding of personnel.
Blinding of participants	Low risk	Quote: "Both drugs were administered as capsules, and were identical in appearance." (p.213)
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "To quantify pain relief, patients made daily recordings." (p.213) Quote: "At the last visit, the patient and the investigator were asked to give an overall assessment of the therapy." (p.213)
Incomplete outcome data for pain and physical function	Low risk	Quote: "Patients who provided information on different efficacy parameters, i.e. who attended all visits, were evaluated for efficacy (evaluable cohort, EVAL)." (p.213) Quote: "The results in the EVAL cohort were consistent with the ITT cohort." (p.215) For tramadol (135 ITT, 81 EVAL, 54 [40%] not included in benefits assessment). For dextropropoxyphene (129 ITT, 109 EVAL, 20 [16%] not included in benefits assessment). Since only participants who attended all their visits were included in the benefits assessment, other participant data would have been missed. Withdrawals due to adverse events: 35.6% with tramadol vs 10.9% with dextropropoxyphene. The reason for missing outcome data was likely to be related to true outcome.
Incomplete outcome data for adverse effects All outcomes	Low risk	Quote: "All patients randomized (intent‐to‐treat cohort, ITT) were included in the analysis of safety." (p.213) Quote: "The results in the EVAL cohort were consistent with the ITT cohort" (p.215) Quote: "A significantly larger number of withdrawals in the tramadol group occurred as a result of adverse events." (p.215) Data on safety analysis were presented in table III for 135 tramadol participants and 129 dextropropoxyphene participants which was the amount of people included in the ITT cohort. However, withdrawals due to adverse events were 35.6% with tramadol vs 10.9% with dextropropoxyphene.
Selective reporting (reporting bias)	Unclear risk	All prespecified outcomes (pain status, physical impairment, adverse signs/symptoms) appeared to have been reported in the results, but we did not have access to the protocol for verification.
Other biases	Low risk	No other sources of bias.