Abstract  Background One of the earliest signs of knee osteoarthritis (OA) is knee pain which correlates with inflammation and disease severity. Knee OA affects 260 million worldwide, and is in similarity with obesity, characterized by ongoing low-grade inflammation. The low grade-inflammation affects the knee-joint area and associations to cartilage degradation and bone remodelling have been shown. Most individuals, however, seek medical care for the first time when they experience knee pain. At this stage, the destruction of the knee is often irreversible. The inflammatory marker C-reactive can be found in both individuals who are obese and individuals with knee OA. It would be beneficial for the many individuals with knee pain at risk of developing knee OA, to be identified at an earlier stage and start treatment and hence slow down the progression of the disease.  Purpose  The purpose was to study associations between obesity, low-grade inflammation, self-reported knee symptoms and the outcome of radiographic knee OA in Swedish individuals with knee pain. Three research questions were formulated. Methods The design of this two-year longitudinal cohort study included Swedish individuals with present knee pain. Data was used to assess obesity and analyse inflammation to determine presence and/or severity of radiographic knee osteoarthritis and evaluate long- and short-term and symptoms and function of the knee. Original data were retrieved from the Cohort profile: the Halland osteoarthritis (HALLOA) cohort–from knee pain to osteoarthritis: a longitudinal observational study in Sweden. Individuals were recruited from healthcare clinics and newspaper advertisement. Age ranged from 32–63 and included data from 60 individuals after two years. Obesity was assessed where body composition was analysed with a bioelectrical impedance analysis. Level of C-reactive protein (CRP) was analysed with ELISA method. The outcome of radiographic knee OA was graded with Ahlbäck classification system in combination with physical examinations of the knees. Self-reported knee symptoms and function were measured with the questionnaire knee injury and osteoarthritis outcome score (KOOS). The data were analysed with the statistical computer software IBM SPSS Statistics.  Results No significant associations were found between the obesity, low-grade inflammation and the outcome of radiographic knee OA in Swedish individuals with knee pain. However, significant associations were found between the odds of developing radiographic knee OA assessed with KOOS for the subgroups pain (p = 0.032), symptom (p = 0.016), Sport/Rec (p = 0.02) and QOL (p = 0.038).  Conclusion KOOS questionnaire should be used for individuals with knee pain to identify individuals at risk of developing knee OA and ensue the disease progression, along with exercise and weight reduction if needed. CRP is not a good marker to measure inflammation in knee OA or use as a predictor tool.