Objective To evaluate the effect and safety of extracorporeal shock wave therapy ( ESWT) for knee osteoarthritis ( KOA) and its effect on the articular cartilage. Methods Sixty-three persons with KOA were randomly divided into an ESWT group ( n=32) and a control group ( n=31) . Both groups received routine knee mus-cle strength training, but the ESWT group was also given ESWT ( a total of 2000 pulses at 8 Hz and 2.5 bar pressure) once a week for four consecutive weeks. The control group was given sham therapy at 0.2 bar with the rest of the pa-rameters the same as in the ESWT group. All of the subjects were assessed using a visual analogue scale ( VAS) , the Western Ontario and McMaster Universities Osteoarthritis Score ( WOMAC) , the Lequesne Index and knee cartilage T2 values before as well as one and 8 weeks after the intervention. Results The average VAS score, WOMAC in-dex, and Lequesne index of the ESWT group at 8 weeks after the treatment were significantly better than those before the intervention, and significantly better than the control group' s averages. The T2 values of the ESWT group at 8 weeks after the treatment were significantly better than before the intervention, though not significantly different from those of the control group at that point. No serious adverse reactions occurred in either group, and all of the minor ad-verse reactions had disappeared before the end of the assessment period. Conclusion ESWT can significantly im-prove the lower limb functioning of KOA patients, and its influence on knee cartilage is within the safe range.