Knee osteoarthritis is one of the common type of arthropathy, the clinical stage of the typical patients belongs to the middle-late stage, so it urges to improve the early diagnosis. At present, magnetic resonance imaging is most used in clinical diagnosis of knee osteoarthritis, and with the development of different MRI sequences, the sequences of early articular cartilage lesions are used in clinic. In the early diagnosis of knee osteoarthritis, the simple and practical methods such as ultrasonography is becoming a trend, and the specific biomarkers of early knee osteoarthritis have become the hot research. This overview article outlined the methods of early diagnosis from the ultrashort echo time MRI, ultrasonography and biomarkers.