Purpose of review: Pain is the most prominent symptom in osteoarthritis. Pain experience is a complex and multifactorial phenomenon. This review, therefore, offers a brief overview of the literature on factors from main pain dimensions and summarizes current evidence for identifying pain phenotypes in knee osteoarthritis.
Recent findings: Peripheral structural damage has been traditionally considered a source of pain and this has strengthened with MRI studies; however, a discordance between structural damage and pain severity suggests individual variations in pain presentation which may be determined by genetic, environmental (obesity), psychological, and neurological factors. Each of the factors may play its role or intact with other factors to contribute to the variation which can partly explain the overall lack of treatment efficacy with the current "one-size-fits-all" treatment approach. Identifying pain phenotypes in knee osteoarthritis is promising to develop individualized treatments; however, the validity and reliability of osteoarthritis pain phenotypes have not been tested in clinical practice. Given the heterogeneity of osteoarthritis pain, peripheral, psychological, and neurological factors are considered key phenotypic dimensions in the identification of pain phenotypes. This new concept allows for patients' stratification for clinical trials, thus providing the potential for individualized interventions in patients with osteoarthritis pain.
Keywords: Knee osteoarthritis; Pain; Phenotypes; Treatment.