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Chronic pain of knee osteoarthritis (KOA) greatly affects the quality of life and functional activities of patients. It is important to clarify the underlying mechanisms of KOA pain and the analgesic effect of different therapies. Neuroimaging technology has been widely used in the basic and clinical research of pain. In the recent years, neuroimaging technology has played an important role in the basic and clinical research of KOA pain. Increasing evidence demonstrates that chronic pain in KOA includes both nociceptive and neuropathic pain. The neuropathic mechanism involved in KOA pain is complex, which may be caused by peripheral or central sensitization. In this paper, we review the regional changes of brain pathophysiology caused by KOA pain based on magnetic resonance imaging (MRI), electroencephalogram (EEG), magnetoencephalogram (MEG), near-infrared spectroscopy (NIRS) and other neuroimaging techniques. We also discuss the central analgesic mechanism of different KOA therapies, with a focus on the latest achievements in the evaluation and prediction of pain. We hope to provide new thoughts for the treatment of KOA pain, especially in the early and middle stages of KOA.

As the two essential components, the white matter and gray matter compose the central nervous system of the brain. Widely known that axons of neurons mainly form the white matter, and these formed nerve fibers are responsible for transmitting information among various brain regions to achieve the coordinated operation of the entire brain. Early research on the white matter could only be done by dissecting living animals or human cadavers, until Basser et al. proposed diffusion tensor imaging (DTI) technology in 1994, which could detect the diffusion characteristics of water in the brain in vivo noninvasively. Accordingly, this technology could be applied to investigate the diffusion movement of water in white matter to obtain the information of direction and micro-anatomy of white matter fiber bundles. With the advancement on the display and analysis of the anatomical structure of white matter fiber bundles, the exploration of microscopic pathological changes, and the assistance of clinical diagnosis and neurophysiological research, DTI technology has become one of the most popular topics in brain science research. Chronic pain refers to pain lasting more than three months, which not only seriously affects the patient's physical and social functions, but also dramatically reduces the quality of life. It was reported that long-term pain stimulation might cause pathological remodeling of the central nervous system, and abnormalities in white matter were found in imaging examinations of patients with chronic pain. This review introduces the quantitative analysis methods of white matter fiber bundle microstructure based on DTI and its application in chronic pain, and further discusses the application value of DTI technology on clinical research of chronic pain.