• Weekly mean of the 24-hour average pain rating using an 11-point numerical Likert scale patient diary [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  

• Patient Global Impression of Improvement [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Western Ontario and McMaster Osteoarthritis Index (WOMAC) physical function, pain, and stiffness subscale [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Weekly mean of the 24-hour worst pain score [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Clinical Global Impression of Severity [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Brief Pain Inventory - Severity and Interference [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Response to treatment - ≥ 30% reduction of weekly mean in 24-hour average pain severity ratings [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Medical Outcomes Study Short Form-36 [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• EuroQoL Questionnaire - 5 Dimension [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Beck Depression Inventory - II [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Hospital Anxiety and Depression Scale anxiety subscale [ Time Frame: over 13 weeks ] [ Designated as safety issue: No ]
  
• Discontinuation rates [ Time Frame: over 13 weeks ] [ Designated as safety issue: Yes ]
  
• Treatment-emergent adverse events [ Time Frame: over 13 weeks ] [ Designated as safety issue: Yes ]
  
• Laboratory assessments [ Time Frame: over 13 weeks ] [ Designated as safety issue: Yes ]
  
• Vital signs [ Time Frame: over 13 weeks ] [ Designated as safety issue: Yes ]
  
• Reduction in weekly mean of 24-hour average pain [ Time Frame: 7-13 weeks ] [ Designated as safety issue: No ]
  
• Response to treatment - ≥ 30% reduction of weekly mean in 24-hour average pain severity ratings [ Time Frame: 7-13 weeks ] [ Designated as safety issue: No ]
  
• Adverse Events, reported as reasons for discontinuations. [ Time Frame: over 13 weeks ] [ Designated as safety issue: Yes ]
  

Inclusion Criteria:

• Male or female outpatients with osteoarthritis knee pain

Exclusion Criteria:

• Cardiovascular, hepatic, renal, respiratory, or hematologic illness, or other medical or psychiatric condition that, in the opinion of the investigator, would compromise participation or be likely to lead to hospitalization during the course of the study.
• Acute liver injury (such as hepatitis) or severe cirrhosis.
• Previous exposure to duloxetine.
• BMI over 40.
• Major depressive disorder.
• Daily use of narcotics.