To investigate and analyze the TCM constitutions and clinical syndromes of knee osteoarthritis (KOA) and explore the relationship between TCM constitutions and clinical syndromes. Methods:A total of 1 591 patients with KOA admitted in orthopedics department in our hospital from Jun. 2013 to Jun. 2016 were selected to investigate and analyze the distribution of TCM constitution and clinical syndrome, and explore the relationship between TCM constitution and clinical syndrome. Results:In the total of 1 591 patients, 461 cases are mild constitution (male/female:198/263) and 1 130 cases are biased constitution (male/female:130/1 000), showing that there was significant difference in gender ratio between men and women in patients with mild constitution and biased constitution (P<0.01). Among 1 130 KOA patients with biased constitution, 625 patients (55.31%) were single biased constitution and 505 cases (44.69%) has compound constitution, mainly with yang deficiency constitution, yin deficiency constitution and qi deficiency constitution. Among the 1 591 cases of KOA patients, there were 410 cases (25.77%) with wind cold damp impediment type, 1042 cases (65.49%) with liver and kidney deficiency type, 139 cases (8.74%) with phlegm-blood stasis blocking type. Liver and kidney deficiency type was significantly higher than the cold damp impediment type and phlegm-blood stasis blocking type (P<0.01). The cold damp impediment type was significantly higher than phlegm-blood stasis blocking type (P<0.01). Yang deficiency, yin deficiency, qi deficiency and mild constitution were the main constitutions in liver and kidney deficiency type. Yang deficiency, yin deficiency and qi deficiency constitution were the main ones in cold damp impediment type. Qi deficiency, phlegm dampness, Yang deficiency and blood stasis constitution were the main ones in phlegm-blood stasis blocking type. Conclusion:In the KOA patients, mild constitution is common in male patients but biased constitution in women and TCM constitutions have a certain correlation with the clinical syndromes.