Objective To explore the electroencephalography (EEG) characteristics of patients with knee osteoarthritis (KOA) which are different from those of healthy subjects during dynamic balance tests, and study the connection and influence between brain activity and KOA. Methods: Fifteen patients with KOA and 17 healthy subjects performed the timed up to go test (TUGT) and 5-times sit to stand test (5STS) . The EEG characteristics of the 4 frequency bands, namely δ (0.5–4 Hz), θ (4–8 Hz), α (8–14 Hz) and β (14–30 Hz)?of 9 electrodes including CZ, C3, C4 in the central lobe, PZ, P3, P4 in the parietal lobe, and OZ, O1, O2 in the occipital lobe of the cerebral cortex of the subjects were recorded. Time and frequency domain analysis were conducted. Results During 5STS, the time-domain amplitudes of electrodes C4, P3, and P4 in the δ band, electrodes C4, P3, and P4 in the θ band, and electrodes P3 and P4 in the β band of KOA patients were significantly higher than those of healthy subjects (P<0.05); the power of electroencephalogram signals of electrodes P3, P4, and O2 in the β band was significantly higher than that of healthy subjects. During TUGT, except that the time-domain amplitude of electrode PZ in the θ band of KOA patients was significantly lower than that of healthy subjects (P<0.05), there was no significant difference in all electrodes in other frequency bands; the power of electroencephalogram signals of electrodes C3, CZ, C4, PZ, P4, O1, OZ, O2 in the δ band and electrodes CZ, P3, PZ, and OZ in the α band and electrodes CZ, P4, OZ, and O2 in the β band was significantly lower than that of healthy subjects (P<0.05). Conclusions Compared with healthy subjects, the activity in the parietal lobe area of the brain of KOA patients during 5STS was stronger, while the brain activity in the central lobe, parietal lobe, and occipital lobe areas of KOA patients during TUGT was weaker than that of healthy subjects. This study may provide some references for clinicians in the prevention and treatment of KOA.