This study was designed to investigate the relationship between radiological severity and clinical and psychological factors in patients with knee osteoarthritis (OA). Patients with knee OA (n = 100) were included in the study. Radiographic staging was done using Kellgren-Lawrence (KL) radiological rating scale. Stage 1-2 changes according to KL were grouped as 'early' and stage 3-4 as 'late' radiological OA. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was used for self-reported disability. Performance-based functional assessments were measured as time needed to walk 15 m and time needed to climb ten steps. Health-related quality of life was assessed by Nottingham Health Profile (NHP). Beck Depression Inventory (BDI) was used to assess the presence and severity of depression. Social isolation was assessed by a related NHP subscale. Significantly higher scores were found in the late stage group for NHP pain, physical mobility and social isolation subscales and all WOMAC subscales. Mean BDI score was significantly higher (p = 0.001) and performance-based functional score was significantly worse (p < 0.001) in the late stage group compared to the early stage. In logistic regression analysis, NHP social isolation subscore was found to be associated with WOMAC pain subscore (p = 0.013, odds ratio [OR] = 1.163; 95% confidence interval [CI], 1.032-1.309) and radiological severity (p = 0.018, OR = 2.924; 95% CI, 1.198-7.136). Radiological severity is an important indicative factor for pain, disability, depression and social isolation. We believe that assessment of psychological involvement in addition to pain and disability might provide benefit in the management of patients with advanced radiological knee OA.