The WOMAC is a statistically validated, 24-item questionnaire assessing current OA symptoms and functional limitations. The Pain subscale score consists of 5 items each rated on a 100mm VAS scale (0mm=no pain to 100mm=extreme pain). In case of premature discontinuation, the last assessment was used to calculate the percentage of change.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

Each day before morning dose, patients assessed arthritis pain in worst knee in a diary using a 5-point rating scale ranging from none to severe. A median score was estimated for each patient each week and re-categorized into different degrees of pain (rounding off to the closest integer). Results are of 12th week (day 78-84).

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

The WOMAC is a statistically validated, 24-item questionnaire assessing current OA symptoms and functional limitations. Stiffness subscale score consists of 2 items each rated on 100mm VAS scale (0mm=no stiffness to 100mm=extreme stiffness). In case of premature discontinuation, the last assessment was used to calculate the percentage of change.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

The WOMAC is a statistically validated, 24-item questionnaire assessing current OA symptoms and functional limitations. Physical Function subscale score consists of 17 items rated on a 100mm VAS scale (0mm=no difficulty to 100mm=extreme difficulty). In case of premature discontinuation, the last assessment was used to calculate percentage of change

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

The WOMAC is a statistically validated, 24-item questionnaire assessing current OA symptoms and functional limitations. Each item is rated on a 100mm VAS scale (0mm=no pain/stiffness/difficulty to 100mm=extreme no pain/stiffness/difficulty). In case of premature discontinuation, the last assessment was used to calculate percentage of change.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

Pain Visual Analogue Scales: Current Pain. Patients indicated their current pain using a 100mm VAS scale ranging from 0=no pain to 100=extreme pain. The percentage of change in current pain was calculated from baseline to week 12. In case of premature discontinuation, the last assessment was used to calculate percentage of change.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

Patients indicated their Least Pain Within Last 24 Hours using a 100mm VAS scale ranging from 0=no pain to 100=extreme pain. The percentage of change was calculated from baseline to week 12. In case of premature discontinuation, the last assessment was used to calculate percentage of change.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

Patients indicated their Worst Pain Within Last 24 Hours using a 100mm VAS scale ranging from 0=no pain to 100=extreme pain. The percentage of change was calculated from baseline to week 12. In case of premature discontinuation, the last assessment was used to calculate percentage of change.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

Patients indicated their Average Pain Within Last 24 Hours using a 100mm VAS scale ranging from 0=no pain to 100=extreme pain. The percentage of change was calculated from baseline to week 12. In case of premature discontinuation, the last assessment was used to calculate percentage of change.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

The walking test is a measure of how many seconds it takes the patient to walk a distance of 15 meters. The change from baseline to week 12 was calculated.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

The Patient Global Rating of Pain is a Likert-scale that answers the question: "How do you rate overall pain relief with the drug?" with 4 possible answers that were dichotomized: "very effective", "effective", and "somewhat effective" were summarized to "effective"; "not effective" remained unchanged.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

Patients were asked: "How have any side effects you may have felt from the drug interfered with day-to-day activities?" with 4 possible answers: "Significantly", "Somewhat", "Minimally", "Not at all".

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

Patients who have previously taken tramadol HCl were asked to compare how they compare the current pain relief to the pain relief felt when previously taking tramadol, using a 4-point Likert-scale: "Worse than before", "Same as before", "Somewhat better now", or "Much better now".

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

Patients who have previously taken tramadol HCl were asked: "Compared to when you were previously taking tramadol, how have any side effects you have felt during this study interfered with your day-to-day activities?". Possible answers were: "Interfered much less now", "Interfered somewhat less now", "Same as before", "Interfered more now".

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

The physician was asked to indicate his overall assessment of the formulation the patient was taking using a 4-point Likert-scale dichotomized for the analysis: Very Effective, Effective, and Somewhat Effective were summarized to Effective; Ineffective remained unchanged.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

The physician was asked to indicate the effectiveness of pain control 24 hours after the most recent dose of tramadol using a 4-point Likert-scale, dichotomized for the analysis: Very Effective, Effective, Somewhat Effective were summarized to Effective; Ineffective remained unchanged.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

As part of the daily diary for the entire study, patients rated the arthritis pain in their worst knee using a five-point scale ranging from 1=none to 5=severe. Mean scores summarizing the entries of the preceding period were calculated.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

As part of the daily diary for the entire study, patients rated the stiffness in their worst knee using a five-point scale ranging from 1=none to 5=severe. Mean scores summarizing the entries of the preceding period were calculated.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

As part of the daily diary for the entire study, patients rated their ability to get things done with their worst knee using a five-point scale ranging from: 1=No problem to 5=A lot of things didn't get done. Mean scores summarizing the entries of the preceding period were calculated.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

As part of the daily diary for the entire study, patients rated their difficulty walking with their worst knee using a five-point scale ranging from 1=No problem to 5=Severe difficulty. Mean scores summarizing the entries of the preceding period were calculated.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.

As part of the daily diary for the entire study, patients rated their difficulty with stairs with their worst knee using a five-point scale ranging from 1=No problem to 5=Severe difficulty. Mean scores summarizing the entries of the preceding period were calculated.

Per protocol population: patients who completed study, had no major protocol deviations before/during trial and had primary efficacy variable rating at end of study. Early drop-outs due to AEs / lack of efficacy were included if they took study drug for >2weeks in maintenance phase and had efficacy assessments within 2 days after end of study drug.