The aim of the study was to evaluate the role of ultrasonography (US) in the management of jumper's knees. Sixty-two cases of clinically suggested jumper's knees, 52 asymptomatic contralateral knees and 100 asymptomatic knees of healthy middle aged men were examined. In the symptomatic group US was normal in 25 cases, all recovered with conservative therapy. In 31 symptomatic knees the findings were consistent with jumper's knee as a hypoechoic lesion located in the upper insertion of the patellar tendon in 23 cases and in the distal insertion in one case. In 7 cases the lesion was situated in the insertion of the quadriceps tendon. Surgery was performed on 20 knees and in all of them there was a lesion matching the lesion detected by US. In 6 cases US findings were pathologic, but different from jumper's knee. US findings consistent with jumper's knee could not be detected in the asymptomatic group.