To determine the therapeutic effect of closed-needle irrigation of knee for pain from osteoarthritis(OA), we conducted a randomized, single blind, 8 week prospective trial study. A comparison was done between the closed-needle irrigation of knee and standard conservative treatment in 30 patients with non-end stage OA of the knee. Statistically significant differences (P＜0.05) favoring closed-needle irrigation of knee over conservative treatment were noted by the Visual Analog Scale for pain in these patients. Overall assessments on effectiveness of therapy by patients(Patient's global assessment) and physician(Knee rating scale) were also statistically superior among closed-needle irrigation group. We conclude that the closed-needle irrigation of knee for the treatment of pain from osteoarthritis is an effective treatment and is superior than the traditional conservative treatment in therapeutic effect.