Arthritis is one of the most common disease of mankind. Major of arthritis is osteoarthritis(OA), but the cause is not clear and the characters are chronic and often progressive. So the management and the pain control of OA are very difficult and adequate ways of controlling it have not been discovered. In the present study we investigated the effects of Knee Intra-articular Injection(KII) of lidocaine with aspirin on OA of the knee. Thirty OA patients with Visual Analogue Scale(VAS) above 8 were studied and they were divided into two groups as follows; Group I(n=15); KII with 1% lidocaine 5 ml Group II(n=15); KII with 2% lidocaine 2 ml and aspirin 2 ml(180 mg, diluted with normal saline) In two groups, KII was done 2 times a week for 4 weeks and we compared the changes of VAS between two groups. The results were as follows; 1) Before the KII, initial mean VAS of group I and II was 8.8 and 8.9. After KII 2 times, VAS of group I and II was 6.6 and 6.4. These deceases were statistically significant, but there was no significant difference of VAS between two groups. 2) After KII 4 times, VAS of group I and II was 6.3 and 5.5, significant decrease was observed in group II. 3) After KII 6 times and 8 times, VAS of group I and II was not decreased anymore, but the VAS of group II was maintained in significant decreased state that of group I. We experienced that KII of lidocaine with aspirin was more effective than that of lidocaine only. So we suggest that KII of mixed solution of lidocaine and apsirin may be one of treatments for OA of the knee.