OBJECTIVES: The prospective multinational Survey of Osteoarthritis Real World Therapies (SORT) was designed to investigate treatment patterns, adequacy of pain relief and quality of life in knee osteoarthritis (OA). This analysis describes the demographic and clinical characteristics most associated with inadequate pain relief (IPR) in knee OA in Portugal. METHODS: Male or female subjects aged ≥50 years with primary knee OA and who were receiving oral or topical analgesics were enrolled between January and December 2011 at seven primary care centers. Pain was assessed using the Brief Pain Inventory (BPI). IPR was defined as a score > 4/10 on the BPI item “What is your pain on average?” reflecting moderate to severe disease. Multivariable logistic regression model was employed to identify the subject characteristics most associated with IPR. RESULTS: Overall, 197 consecutive patients were analyzed. The mean age was 67.0 ± 8.6 years and 78.2% were female. The mean duration of knee OA was 6.2 ± 6.3 years. The most common comorbidities were hypertension (64.0%), hyperlipidemia (58.4%), disability (41.6%) and depression (37.6%). Non­steroidal anti­inflammatory drugs were the most frequently used analgesics. IPR was reported by 51.3% of patients (95%CI 44.1%, 58.4%). Disability, depression and diabetes were more frequent among patients with IPR than in patients with Non-IPR (p<0.05). No statistically significant differences were observed in the type and mean number of different classes of medication used by IPR and Non-IPR patients. Female gender (adjusted odds ratio - OR 2.15 [95%CI 1.1, 4.5]), diabetes (adjusted OR 3.1 [95%CI 1.3, 7.7]) and depression (adjusted OR 2.24 [95%CI 1.2, 4.3]) were associated with higher risk of IPR. CONCLUSIONS: Our findings indicate that improvements are needed in the management of pain in knee OA in order to achieve better outcomes and highlight the requisite for further interventions targeting frequent comorbid conditions in knee OA in Portugal.