Plasma fatty acids reflect pain, disability, and psychological well-being in knee osteoarthritis in a longitudinal study with joint replacement surgery

We investigated the associations of pro- and anti-inflammatory fatty acids (FAs) with cartilage degradation, functional limitations, pain, and psychological well-being in knee osteoarthritis (KOA). Fasting plasma samples were obtained from controls (n = 12) and from end-stage KOA patients at baseline (n = 13), and 3 months (n = 11) and 12 months (n = 9) after knee replacement surgery. FA composition in total lipids was analyzed with gas chromatography and mass spectrometry. Cartilage loss was determined by magnetic resonance imaging, and knee pain and disability by physical performance and quantitative sensory testing, neuromuscular examination, and several questionnaires. The associations between variables were tested with the univariate analysis of variance adjusted for age and body mass index. KOA was characterized with elevated baseline 16:1n-7 percentages, while the proportions of 24:0 decreased 12 months after surgery and those of 24:1n-9 decreased 3 and 12 months after surgery. Several FA variables, such as 20:3n-6, 20:4n-6, long-chain saturated FAs, and 24:1n-9, were associated with pain, stiffness, disability, pain self-efficacy, or mental health. Circulating FAs can predict KOA symptoms, independent of age and body adiposity, and provide promising targets to design novel pain treatments.